kwant/system.py

-# Copyright 2011-2013 Kwant authors.
+# Copyright 2011-2019 Kwant authors.
 #
 # This file is part of Kwant.  It is subject to the license terms in the file
 # LICENSE.rst found in the top-level directory of this distribution and at
@@ -8,13 +8,269 @@
 
 """Low-level interface of systems"""
 
-__all__ = ['System', 'FiniteSystem', 'InfiniteSystem']
+__all__ = [
+    'Site', 'SiteArray', 'SiteFamily',
+    'System', 'VectorizedSystem', 'FiniteSystem', 'FiniteVectorizedSystem',
+    'InfiniteSystem', 'InfiniteVectorizedSystem',
+]
 
 import abc
 import warnings
+import operator
 from copy import copy
+from collections import namedtuple
+from functools import total_ordering, lru_cache
+import numpy as np
 from . import _system
-from ._common  import deprecate_args
+from ._common  import deprecate_args, KwantDeprecationWarning
+
+
+
+################ Sites and Site families
+
+class Site(tuple):
+    """A site, member of a `SiteFamily`.
+
+    Sites are the vertices of the graph which describes the tight binding
+    system in a `Builder`.
+
+    A site is uniquely identified by its family and its tag.
+
+    Parameters
+    ----------
+    family : an instance of `SiteFamily`
+        The 'type' of the site.
+    tag : a hashable python object
+        The unique identifier of the site within the site family, typically a
+        vector of integers.
+
+    Raises
+    ------
+    ValueError
+        If `tag` is not a proper tag for `family`.
+
+    Notes
+    -----
+    For convenience, ``family(*tag)`` can be used instead of ``Site(family,
+    tag)`` to create a site.
+
+    The parameters of the constructor (see above) are stored as instance
+    variables under the same names.  Given a site ``site``, common things to
+    query are thus ``site.family``, ``site.tag``, and ``site.pos``.
+    """
+    __slots__ = ()
+
+    family = property(operator.itemgetter(0),
+                      doc="The site family to which the site belongs.")
+    tag = property(operator.itemgetter(1), doc="The tag of the site.")
+
+
+    def __new__(cls, family, tag, _i_know_what_i_do=False):
+        if _i_know_what_i_do:
+            return tuple.__new__(cls, (family, tag))
+        try:
+            tag = family.normalize_tag(tag)
+        except (TypeError, ValueError) as e:
+            msg = 'Tag {0} is not allowed for site family {1}: {2}'
+            raise type(e)(msg.format(repr(tag), repr(family), e.args[0]))
+        return tuple.__new__(cls, (family, tag))
+
+    def __repr__(self):
+        return 'Site({0}, {1})'.format(repr(self.family), repr(self.tag))
+
+    def __str__(self):
+        sf = self.family
+        return '<Site {0} of {1}>'.format(self.tag, sf.name if sf.name else sf)
+
+    def __getnewargs__(self):
+        return (self.family, self.tag, True)
+
+    @property
+    def pos(self):
+        """Real space position of the site.
+
+        This relies on ``family`` having a ``pos`` method (see `SiteFamily`).
+        """
+        return self.family.pos(self.tag)
+
+
+class SiteArray:
+    """An array of sites, members of a `SiteFamily`.
+
+    Parameters
+    ----------
+    family : an instance of `SiteFamily`
+        The 'type' of the sites.
+    tags : a sequence of python objects
+        Sequence of unique identifiers of the sites within the
+        site array family, typically vectors of integers.
+
+    Raises
+    ------
+    ValueError
+        If `tags` are not proper tags for `family`.
+
+    See Also
+    --------
+    kwant.system.Site
+    """
+
+    def __init__(self, family, tags):
+        self.family = family
+        try:
+            tags = family.normalize_tags(tags)
+        except (TypeError, ValueError) as e:
+            msg = 'Tags {0} are not allowed for site family {1}: {2}'
+            raise type(e)(msg.format(repr(tags), repr(family), e.args[0]))
+        self.tags = tags
+
+    def __repr__(self):
+        return 'SiteArray({0}, {1})'.format(repr(self.family), repr(self.tags))
+
+    def __str__(self):
+        sf = self.family
+        return ('<SiteArray {0} of {1}>'
+                .format(self.tags, sf.name if sf.name else sf))
+
+    def __len__(self):
+        return len(self.tags)
+
+    def __eq__(self, other):
+        if not isinstance(other, SiteArray):
+            raise NotImplementedError()
+        return self.family == other.family and np.all(self.tags == other.tags)
+
+    def positions(self):
+        """Real space position of the site.
+
+        This relies on ``family`` having a ``pos`` method (see `SiteFamily`).
+        """
+        return self.family.positions(self.tags)
+
+
+@total_ordering
+class SiteFamily:
+    """Abstract base class for site families.
+
+    Site families are the 'type' of `Site` objects.  Within a family, individual
+    sites are uniquely identified by tags.  Valid tags must be hashable Python
+    objects, further details are up to the family.
+
+    Site families must be immutable and fully defined by their initial
+    arguments.  They must inherit from this abstract base class and call its
+    __init__ function providing it with two arguments: a canonical
+    representation and a name.  The canonical representation will be returned as
+    the objects representation and must uniquely identify the site family
+    instance.  The name is a string used to distinguish otherwise identical site
+    families.  It may be empty. ``norbs`` defines the number of orbitals
+    on sites associated with this site family; it may be `None`, in which case
+    the number of orbitals is not specified.
+
+
+    All site families must define either 'normalize_tag' or 'normalize_tags',
+    which brings a tag (or, in the latter case, a sequence of tags) to the
+    standard format for this site family.
+
+    Site families may also implement methods ``pos(tag)`` and
+    ``positions(tags)``, which return a vector of realspace coordinates or an
+    array of vectors of realspace coordinates of the site(s) belonging to this
+    family with the given tag(s). These methods are used in plotting routines.
+    ``positions(tags)`` should return an array with shape ``(N, M)`` where
+    ``N`` is the length of ``tags``, and ``M`` is the realspace dimension.
+
+    If the ``norbs`` of a site family are provided, and sites of this family
+    are used to populate a `~kwant.builder.Builder`, then the associated
+    Hamiltonian values must have the correct shape. That is, if a site family
+    has ``norbs = 2``, then any on-site terms for sites belonging to this
+    family should be 2x2 matrices. Similarly, any hoppings to/from sites
+    belonging to this family must have a matrix structure where there are two
+    rows/columns. This condition applies equally to Hamiltonian values that
+    are given by functions. If this condition is not satisfied, an error will
+    be raised.
+    """
+
+    def __init__(self, canonical_repr, name, norbs):
+        self.canonical_repr = canonical_repr
+        self.hash = hash(canonical_repr)
+        self.name = name
+        if norbs is None:
+            warnings.warn("Not specfying norbs is deprecated. Always specify "
+                          "norbs when creating site families.",
+                          KwantDeprecationWarning, stacklevel=3)
+        if norbs is not None:
+            if int(norbs) != norbs or norbs <= 0:
+                raise ValueError('The norbs parameter must be an integer > 0.')
+            norbs = int(norbs)
+        self.norbs = norbs
+
+    def __init_subclass__(cls, **kwargs):
+        super().__init_subclass__(**kwargs)
+        if (cls.normalize_tag is SiteFamily.normalize_tag
+            and cls.normalize_tags is SiteFamily.normalize_tags):
+            raise TypeError("Must redefine either 'normalize_tag' or "
+                            "'normalize_tags'")
+
+    def __repr__(self):
+        return self.canonical_repr
+
+    def __str__(self):
+        if self.name:
+            msg = '<{0} site family {1}{2}>'
+        else:
+            msg = '<unnamed {0} site family{2}>'
+        orbs = ' with {0} orbitals'.format(self.norbs) if self.norbs else ''
+        return msg.format(self.__class__.__name__, self.name, orbs)
+
+    def __hash__(self):
+        return self.hash
+
+    def __eq__(self, other):
+        try:
+            return self.canonical_repr == other.canonical_repr
+        except AttributeError:
+            return False
+
+    def __ne__(self, other):
+        try:
+            return self.canonical_repr != other.canonical_repr
+        except AttributeError:
+            return True
+
+    def __lt__(self, other):
+        # If this raises an AttributeError, we were trying
+        # to compare it to something non-comparable anyway.
+        return self.canonical_repr < other.canonical_repr
+
+    def normalize_tag(self, tag):
+        """Return a normalized version of the tag.
+
+        Raises TypeError or ValueError if the tag is not acceptable.
+        """
+        tag, = self.normalize_tags([tag])
+        return tag
+
+    def normalize_tags(self, tags):
+        """Return a normalized version of the tags.
+
+        Raises TypeError or ValueError if the tags are not acceptable.
+        """
+        return np.array([self.normalize_tag(tag) for tag in tags])
+
+    def __call__(self, *tag):
+        """
+        A convenience function.
+
+        This function allows to write fam(1, 2) instead of Site(fam, (1, 2)).
+        """
+        # Catch a likely and difficult to find mistake.
+        if tag and isinstance(tag[0], tuple):
+            raise ValueError('Use site_family(1, 2) instead of '
+                             'site_family((1, 2))!')
+        return Site(self, tag)
+
+
+
+################ Systems
 
 
 class System(metaclass=abc.ABCMeta):
@@ -92,12 +348,100 @@ class System(metaclass=abc.ABCMeta):
         details = ', and '.join((', '.join(details[:-1]), details[-1]))
         return '<{} with {}>'.format(self.__class__.__name__, details)
 
+    hamiltonian_submatrix = _system.hamiltonian_submatrix
+
+
+Term = namedtuple(
+    "Term",
+    ["subgraph", "hermitian", "parameters"],
+)
+
+
+class VectorizedSystem(System, metaclass=abc.ABCMeta):
+    """Abstract general low-level system with support for vectorization.
+
+    Attributes
+    ----------
+    graph : kwant.graph.CGraph
+        The system graph.
+    subgraphs : sequence of tuples
+        Each subgraph has the form '((idx1, idx2), (offsets1, offsets2))'
+        where 'offsets1' and 'offsets2' index sites within the site arrays
+        indexed by 'idx1' and 'idx2'.
+    terms : sequence of tuples
+        Each tuple has the following structure:
+        (subgraph: int, hermitian: bool, parameters: List(str))
+        'subgraph' indexes 'subgraphs' and supplies the to/from sites of this
+        term. 'hermitian' is 'True' if the term needs its Hermitian
+        conjugate to be added when evaluating the Hamiltonian, and 'parameters'
+        contains a list of parameter names used when evaluating this term.
+    site_arrays : sequence of SiteArray
+        The sites of the system.
+    site_ranges : None or Nx3 integer array
+        Has 1 row per site array, plus one extra row.  Each row consists
+        of ``(first_site, norbs, orb_offset)``: the index of the first
+        site in the site array, the number of orbitals on each site in
+        the site array, and the offset of the first orbital of the first
+        site in the site array.  In addition, the final row has the form
+        ``(len(graph.num_nodes), 0, tot_norbs)`` where ``tot_norbs`` is the
+        total number of orbitals in the system.  ``None`` if any site array
+        in 'site_arrays' does not have 'norbs' specified. Note 'site_ranges'
+        is directly computable from 'site_arrays'.
+    parameters : frozenset of strings
+        The names of the parameters on which the system depends. This attribute
+        is provisional and may be changed in a future version of Kwant
+
+    Notes
+    -----
+    The sites of the system are indexed by integers ranging from 0 to
+    ``self.graph.num_nodes - 1``.
+
+    Optionally, a class derived from ``System`` can provide a method ``pos`` which
+    is assumed to return the real-space position of a site given its index.
+    """
+    @abc.abstractmethod
+    def hamiltonian_term(self, term_number, selector=slice(None),
+                         args=(), params=None):
+        """Return the Hamiltonians for hamiltonian term number k.
 
-# Add a C-implemented function as an unbound method to class System.
-System.hamiltonian_submatrix = _system.hamiltonian_submatrix
+        Parameters
+        ----------
+        term_number : int
+            The number of the term to evaluate.
+        selector : slice or sequence of int, default: slice(None)
+            The elements of the term to evaluate.
+        args : tuple
+            Positional arguments to the term. (Deprecated)
+        params : dict
+            Keyword parameters to the term
 
+        Returns
+        -------
+        hamiltonian : 3d complex array
+            Has shape ``(N, P, Q)`` where ``N`` is the number of matrix
+            elements in this term (or the number selected by 'selector'
+            if provided), ``P`` and ``Q`` are the number of orbitals in the
+            'to' and 'from' site arrays associated with this term.
 
-class FiniteSystem(System, metaclass=abc.ABCMeta):
+        Providing positional arguments via 'args' is deprecated,
+        instead, provide named parameters as a dictionary via 'params'.
+        """
+    @property
+    @lru_cache(1)
+    def site_ranges(self):
+        site_offsets = np.cumsum([0] + [len(arr) for arr in self.site_arrays])
+        norbs = [arr.family.norbs for arr in self.site_arrays] + [0]
+        if any(norb is None for norb in norbs):
+            return None
+        orb_offsets = np.cumsum(
+            [0] + [len(arr) * arr.family.norbs for arr in self.site_arrays]
+        )
+        return np.array([site_offsets, norbs, orb_offsets]).transpose()
+
+    hamiltonian_submatrix = _system.vectorized_hamiltonian_submatrix
+
+
+class FiniteSystemMixin(metaclass=abc.ABCMeta):
     """Abstract finite low-level system, possibly with leads.
 
     Attributes
@@ -220,7 +564,19 @@ class FiniteSystem(System, metaclass=abc.ABCMeta):
         return symmetries.validate(ham)
 
 
-class InfiniteSystem(System, metaclass=abc.ABCMeta):
+class FiniteSystem(System, FiniteSystemMixin, metaclass=abc.ABCMeta):
+    pass
+
+
+class FiniteVectorizedSystem(VectorizedSystem, FiniteSystemMixin, metaclass=abc.ABCMeta):
+    pass
+
+
+def is_finite(syst):
+    return isinstance(syst, (FiniteSystem, FiniteVectorizedSystem))
+
+
+class InfiniteSystemMixin(metaclass=abc.ABCMeta):
     """Abstract infinite low-level system.
 
     An infinite system consists of an infinite series of identical cells.
@@ -261,30 +617,10 @@ class InfiniteSystem(System, metaclass=abc.ABCMeta):
     infinite system.  The other scheme has the numbers of site 0 and 1
     exchanged, as well as of site 3 and 4.
 
+    Sites in the fundamental domain cell must belong to a different site array
+    than the sites in the previous cell. In the above example this means that
+    sites '(0, 1, 2)' and '(3, 4)' must belong to different site arrays.
     """
-    @deprecate_args
-    def cell_hamiltonian(self, args=(), sparse=False, *, params=None):
-        """Hamiltonian of a single cell of the infinite system.
-
-        Providing positional arguments via 'args' is deprecated,
-        instead, provide named parameters as a dictionary via 'params'.
-        """
-        cell_sites = range(self.cell_size)
-        return self.hamiltonian_submatrix(args, cell_sites, cell_sites,
-                                          sparse=sparse, params=params)
-
-    @deprecate_args
-    def inter_cell_hopping(self, args=(), sparse=False, *, params=None):
-        """Hopping Hamiltonian between two cells of the infinite system.
-
-        Providing positional arguments via 'args' is deprecated,
-        instead, provide named parameters as a dictionary via 'params'.
-        """
-        cell_sites = range(self.cell_size)
-        interface_sites = range(self.cell_size, self.graph.num_nodes)
-        return self.hamiltonian_submatrix(args, cell_sites, interface_sites,
-                                          sparse=sparse, params=params)
-
     @deprecate_args
     def modes(self, energy=0, args=(), *, params=None):
         """Return mode decomposition of the lead
@@ -368,6 +704,41 @@ class InfiniteSystem(System, metaclass=abc.ABCMeta):
         return list(broken)
 
 
+class InfiniteSystem(System, InfiniteSystemMixin, metaclass=abc.ABCMeta):
+
+    @deprecate_args
+    def cell_hamiltonian(self, args=(), sparse=False, *, params=None):
+        """Hamiltonian of a single cell of the infinite system.
+
+        Providing positional arguments via 'args' is deprecated,
+        instead, provide named parameters as a dictionary via 'params'.
+        """
+        cell_sites = range(self.cell_size)
+        return self.hamiltonian_submatrix(args, cell_sites, cell_sites,
+                                          sparse=sparse, params=params)
+
+    @deprecate_args
+    def inter_cell_hopping(self, args=(), sparse=False, *, params=None):
+        """Hopping Hamiltonian between two cells of the infinite system.
+
+        Providing positional arguments via 'args' is deprecated,
+        instead, provide named parameters as a dictionary via 'params'.
+        """
+        cell_sites = range(self.cell_size)
+        interface_sites = range(self.cell_size, self.graph.num_nodes)
+        return self.hamiltonian_submatrix(args, cell_sites, interface_sites,
+                                          sparse=sparse, params=params)
+
+
+class InfiniteVectorizedSystem(VectorizedSystem, InfiniteSystemMixin, metaclass=abc.ABCMeta):
+    cell_hamiltonian = _system.vectorized_cell_hamiltonian
+    inter_cell_hopping = _system.vectorized_inter_cell_hopping
+
+
+def is_infinite(syst):
+    return isinstance(syst, (InfiniteSystem, InfiniteVectorizedSystem))
+
+
 class PrecalculatedLead:
     def __init__(self, modes=None, selfenergy=None):
         """A general lead defined by its self energy.

kwant/tests/test_builder.py

-# Copyright 2011-2018 Kwant authors.
+# Copyright 2011-2019 Kwant authors.
 #
 # This file is part of Kwant.  It is subject to the license terms in the file
 # LICENSE.rst found in the top-level directory of this distribution and at
@@ -19,8 +19,8 @@ from pytest import raises, warns
 from numpy.testing import assert_almost_equal
 
 import kwant
-from kwant import builder
-from kwant._common import ensure_rng
+from kwant import builder, system
+from kwant._common import ensure_rng, KwantDeprecationWarning
 
 
 def test_bad_keys():
@@ -28,7 +28,7 @@ def test_bad_keys():
     def setitem(key):
         syst[key] = None
 
-    fam = builder.SimpleSiteFamily()
+    fam = builder.SimpleSiteFamily(norbs=1)
     syst = builder.Builder()
 
     failures = [
@@ -97,9 +97,9 @@ def test_bad_keys():
 
 def test_site_families():
     syst = builder.Builder()
-    fam = builder.SimpleSiteFamily()
-    ofam = builder.SimpleSiteFamily()
-    yafam = builder.SimpleSiteFamily('another_name')
+    fam = builder.SimpleSiteFamily(norbs=1)
+    ofam = builder.SimpleSiteFamily(norbs=1)
+    yafam = builder.SimpleSiteFamily('another_name', norbs=1)
 
     syst[fam(0)] = 7
     assert syst[fam(0)] == 7
@@ -162,7 +162,7 @@ class VerySimpleSymmetry(builder.Symmetry):
 # made.
 def check_construction_and_indexing(sites, sites_fd, hoppings, hoppings_fd,
                                     unknown_hoppings, sym=None):
-    fam = builder.SimpleSiteFamily()
+    fam = builder.SimpleSiteFamily(norbs=1)
     syst = builder.Builder(sym)
     t, V = 1.0j, 0.0
     syst[sites] = V
@@ -212,7 +212,7 @@ def check_construction_and_indexing(sites, sites_fd, hoppings, hoppings_fd,
 
 def test_construction_and_indexing():
     # Without symmetry
-    fam = builder.SimpleSiteFamily()
+    fam = builder.SimpleSiteFamily(norbs=1)
     sites = [fam(0, 0), fam(0, 1), fam(1, 0)]
     hoppings = [(fam(0, 0), fam(0, 1)),
                 (fam(0, 1), fam(1, 0)),
@@ -250,7 +250,7 @@ def test_hermitian_conjugation():
             raise ValueError
 
     syst = builder.Builder()
-    fam = builder.SimpleSiteFamily()
+    fam = builder.SimpleSiteFamily(norbs=1)
     syst[fam(0)] = syst[fam(1)] = ta.identity(2)
 
     syst[fam(0), fam(1)] = f
@@ -266,7 +266,7 @@ def test_hermitian_conjugation():
 def test_value_equality_and_identity():
     m = ta.array([[1, 2], [3j, 4j]])
     syst = builder.Builder()
-    fam = builder.SimpleSiteFamily()
+    fam = builder.SimpleSiteFamily(norbs=1)
 
     syst[fam(0)] = m
     syst[fam(1)] = m
@@ -290,12 +290,28 @@ def random_hopping_integral(rng):
 
 
 def check_onsite(fsyst, sites, subset=False, check_values=True):
+    vectorized = isinstance(fsyst, (system.FiniteVectorizedSystem, system.InfiniteVectorizedSystem))
+
+    if vectorized:
+        site_offsets = np.cumsum([0] + [len(s) for s in fsyst.site_arrays])
+
     freq = {}
     for node in range(fsyst.graph.num_nodes):
         site = fsyst.sites[node].tag
         freq[site] = freq.get(site, 0) + 1
         if check_values and site in sites:
-            assert fsyst.onsites[node][0] is sites[site]
+            if vectorized:
+                term = fsyst._onsite_term_by_site_id[node]
+                value = fsyst._term_values[term]
+                if callable(value):
+                    assert value is sites[site]
+                else:
+                    (w, _), (off, _) = fsyst.subgraphs[fsyst.terms[term].subgraph]
+                    node_off = node - site_offsets[w]
+                    selector = np.searchsorted(off, node_off)
+                    assert np.allclose(value[selector], sites[site])
+            else:
+                assert fsyst.onsites[node][0] is sites[site]
     if not subset:
         # Check that all sites of `fsyst` are in `sites`.
         for site in freq.keys():
@@ -306,24 +322,50 @@ def check_onsite(fsyst, sites, subset=False, check_values=True):
 
 
 def check_hoppings(fsyst, hops):
+    vectorized = isinstance(fsyst, (system.FiniteVectorizedSystem, system.InfiniteVectorizedSystem))
+
+    if vectorized:
+        site_offsets = np.cumsum([0] + [len(s) for s in fsyst.site_arrays])
+
     assert fsyst.graph.num_edges == 2 * len(hops)
     for edge_id, edge in enumerate(fsyst.graph):
-        tail, head = edge
-        tail = fsyst.sites[tail].tag
-        head = fsyst.sites[head].tag
-        value = fsyst.hoppings[edge_id][0]
-        if value is builder.Other:
-            assert (head, tail) in hops
+        i, j = edge
+        tail = fsyst.sites[i].tag
+        head = fsyst.sites[j].tag
+
+        if vectorized:
+            term = fsyst._hopping_term_by_edge_id[edge_id]
+            if term < 0:  # Hermitian conjugate
+                assert (head, tail) in hops
+            else:
+                value = fsyst._term_values[term]
+                assert (tail, head) in hops
+                if callable(value):
+                    assert value is hops[tail, head]
+                else:
+                    dtype = np.dtype([('f0', int), ('f1', int)])
+                    subgraph = fsyst.terms[term].subgraph
+                    (to_w, from_w), hoppings = fsyst.subgraphs[subgraph]
+                    hop = (i - site_offsets[to_w], j - site_offsets[from_w])
+                    hop = np.array(hop, dtype=dtype)
+                    hoppings = hoppings.transpose().view(dtype).reshape(-1)
+                    selector = np.recarray.searchsorted(hoppings, hop)
+                    assert np.allclose(value[selector], hops[tail, head])
         else:
-            assert (tail, head) in hops
-            assert value is hops[tail, head]
+            value = fsyst.hoppings[edge_id][0]
+            if value is builder.Other:
+                assert (head, tail) in hops
+            else:
+                assert (tail, head) in hops
+                assert value is hops[tail, head]
 
 def check_id_by_site(fsyst):
     for i, site in enumerate(fsyst.sites):
         assert fsyst.id_by_site[site] == i
 
 
-def test_finalization():
+@pytest.mark.parametrize("vectorize", [False, True])
+def test_finalization(vectorize):
     """Test the finalization of finite and infinite systems.
 
     In order to exactly verify the finalization, low-level features of the
@@ -377,8 +419,8 @@ def test_finalization():
     neighbors = sorted(neighbors)
 
     # Build scattering region from blueprint and test it.
-    syst = builder.Builder()
-    fam = kwant.lattice.general(ta.identity(2))
+    syst = builder.Builder(vectorize=vectorize)
+    fam = kwant.lattice.general(ta.identity(2), norbs=1)
     for site, value in sr_sites.items():
         syst[fam(*site)] = value
     for hop, value in sr_hops.items():
@@ -388,7 +430,7 @@ def test_finalization():
     check_onsite(fsyst, sr_sites)
     check_hoppings(fsyst, sr_hops)
     # check that sites are sorted
-    assert fsyst.sites == tuple(sorted(fam(*site) for site in sr_sites))
+    assert tuple(fsyst.sites) == tuple(sorted(fam(*site) for site in sr_sites))
 
     # Build lead from blueprint and test it.
     lead = builder.Builder(kwant.TranslationalSymmetry((size, 0)))
@@ -421,12 +463,12 @@ def test_finalization():
 
     # Attach lead with improper interface.
     syst.leads[-1] = builder.BuilderLead(
-        lead, 2 * tuple(builder.Site(fam, n) for n in neighbors))
+        lead, 2 * tuple(system.Site(fam, n) for n in neighbors))
     raises(ValueError, syst.finalized)
 
     # Attach lead properly.
     syst.leads[-1] = builder.BuilderLead(
-        lead, (builder.Site(fam, n) for n in neighbors))
+        lead, (system.Site(fam, n) for n in neighbors))
     fsyst = syst.finalized()
     assert len(fsyst.lead_interfaces) == 1
     assert ([fsyst.sites[i].tag for i in fsyst.lead_interfaces[0]] ==
@@ -434,15 +476,15 @@ def test_finalization():
 
     # test that we cannot finalize a system with a badly sorted interface order
     raises(ValueError, builder.InfiniteSystem, lead,
-           [builder.Site(fam, n) for n in reversed(neighbors)])
+           [system.Site(fam, n) for n in reversed(neighbors)])
     # site ordering independent of whether interface was specified
-    flead_order = builder.InfiniteSystem(lead, [builder.Site(fam, n)
+    flead_order = builder.InfiniteSystem(lead, [system.Site(fam, n)
                                                 for n in neighbors])
-    assert flead.sites == flead_order.sites
+    assert tuple(flead.sites) == tuple(flead_order.sites)
 
 
     syst.leads[-1] = builder.BuilderLead(
-        lead, (builder.Site(fam, n) for n in neighbors))
+        lead, (system.Site(fam, n) for n in neighbors))
     fsyst = syst.finalized()
     assert len(fsyst.lead_interfaces) == 1
     assert ([fsyst.sites[i].tag for i in fsyst.lead_interfaces[0]] ==
@@ -457,44 +499,62 @@ def test_finalization():
     raises(ValueError, lead.finalized)
 
 
-def test_site_ranges():
+def _make_system_from_sites(sites, vectorize):
+    syst = builder.Builder(vectorize=vectorize)
+    for s in sites:
+        norbs = s.family.norbs
+        if norbs:
+            syst[s] = np.eye(s.family.norbs)
+        else:
+            syst[s] = None
+    return syst.finalized()
+
+
+@pytest.mark.parametrize("vectorize", [False, True])
+def test_site_ranges(vectorize):
     lat1a = kwant.lattice.chain(norbs=1, name='a')
     lat1b = kwant.lattice.chain(norbs=1, name='b')
     lat2 = kwant.lattice.chain(norbs=2)
-    site_ranges = builder._site_ranges
 
     # simple case -- single site family
     for lat in (lat1a, lat2):
         sites = list(map(lat, range(10)))
-        ranges = site_ranges(sites)
+        syst = _make_system_from_sites(sites, vectorize)
+        ranges = syst.site_ranges
         expected = [(0, lat.norbs, 0), (10, 0, 10 * lat.norbs)]
-        assert ranges == expected
+        assert np.array_equal(ranges, expected)
 
     # pair of site families
-    sites = it.chain(map(lat1a, range(4)), map(lat1b, range(6)),
-                     map(lat1a, range(4)))
-    expected = [(0, 1, 0), (4, 1, 4), (10, 1, 10), (14, 0, 14)]
-    assert expected == site_ranges(tuple(sites))
+    sites = it.chain(map(lat1a, range(4)), map(lat1b, range(6)))
+    syst = _make_system_from_sites(sites, vectorize)
+    expected = [(0, 1, 0), (4, 1, 4), (10, 0, 10)]
+    assert np.array_equal(expected, syst.site_ranges)
     sites = it.chain(map(lat2, range(4)), map(lat1a, range(6)),
                      map(lat1b, range(4)))
+    syst = _make_system_from_sites(sites, vectorize)
     expected = [(0, 2, 0), (4, 1, 4*2), (10, 1, 4*2+6), (14, 0, 4*2+10)]
-    assert expected == site_ranges(tuple(sites))
+    assert np.array_equal(expected, syst.site_ranges)
 
     # test with an actual builder
     for lat in (lat1a, lat2):
         sites = list(map(lat, range(10)))
-        syst = kwant.Builder()
+        syst = kwant.Builder(vectorize=vectorize)
         syst[sites] = np.eye(lat.norbs)
         ranges = syst.finalized().site_ranges
         expected = [(0, lat.norbs, 0), (10, 0, 10 * lat.norbs)]
-        assert ranges == expected
-        # poison system with a single site with no norbs defined
-        syst[kwant.lattice.chain()(0)] = 1
-        ranges = syst.finalized().site_ranges
-        assert ranges == None
-
-
-def test_hamiltonian_evaluation():
+        assert np.array_equal(ranges, expected)
+        if not vectorize:  # vectorized systems *must* have all norbs
+            # poison system with a single site with no norbs defined.
+            # Also catch the deprecation warning.
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore")
+                syst[kwant.lattice.chain(norbs=None)(0)] = 1
+            ranges = syst.finalized().site_ranges
+            assert ranges is None
+
+
+@pytest.mark.parametrize("vectorize", [False, True])
+def test_hamiltonian_evaluation(vectorize):
     def f_onsite(site):
         return site.tag[0]
 
@@ -502,14 +562,26 @@ def test_hamiltonian_evaluation():
         a, b = a.tag, b.tag
         return complex(a[0] + b[0], a[1] - b[1])
 
+    def f_onsite_vectorized(sites):
+        return sites.tags[:, 0]
+
+    def f_hopping_vectorized(a, b):
+        a, b = a.tags, b.tags
+        return a[:, 0] + b[:, 0] + 1j * (a[:, 1] - b[:, 1])
+
     tags = [(0, 0), (1, 1), (2, 2), (3, 3)]
     edges = [(0, 1), (0, 2), (0, 3), (1, 2)]
 
-    syst = builder.Builder()
-    fam = builder.SimpleSiteFamily()
+    syst = builder.Builder(vectorize=vectorize)
+    fam = builder.SimpleSiteFamily(norbs=1)
     sites = [fam(*tag) for tag in tags]
-    syst[(fam(*tag) for tag in tags)] = f_onsite
-    syst[((fam(*tags[i]), fam(*tags[j])) for (i, j) in edges)] = f_hopping
+    hoppings = [(sites[i], sites[j]) for i, j in edges]
+    if vectorize:
+        syst[sites] = f_onsite_vectorized
+        syst[hoppings] = f_hopping_vectorized
+    else:
+        syst[sites] = f_onsite
+        syst[hoppings] = f_hopping
     fsyst = syst.finalized()
 
     assert fsyst.graph.num_nodes == len(tags)
@@ -518,12 +590,16 @@ def test_hamiltonian_evaluation():
     for i in range(len(tags)):
         site = fsyst.sites[i]
         assert site in sites
-        assert fsyst.hamiltonian(i, i) == syst[site](site)
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+            assert fsyst.hamiltonian(i, i) == f_onsite(site)
 
     for t, h in fsyst.graph:
         tsite = fsyst.sites[t]
         hsite = fsyst.sites[h]
-        assert fsyst.hamiltonian(t, h) == syst[tsite, hsite](tsite, hsite)
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+            assert fsyst.hamiltonian(t, h) == f_hopping(tsite, hsite)
 
     # test when user-function raises errors
     def onsite_raises(site):
@@ -536,13 +612,18 @@ def test_hamiltonian_evaluation():
         a, b = hop
         # exceptions are converted to kwant.UserCodeError and we add our message
         with raises(kwant.UserCodeError) as exc_info:
-            fsyst.hamiltonian(a, a)
+            with warnings.catch_warnings():
+                warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+                fsyst.hamiltonian(a, a)
         msg = 'Error occurred in user-supplied value function "onsite_raises"'
         assert msg in str(exc_info.value)
 
         for hop in [(a, b), (b, a)]:
             with raises(kwant.UserCodeError) as exc_info:
-                fsyst.hamiltonian(*hop)
+                with warnings.catch_warnings():
+                    # Ignore deprecation warnings for 'hamiltonian'
+                    warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+                    fsyst.hamiltonian(*hop)
             msg = ('Error occurred in user-supplied '
                    'value function "hopping_raises"')
             assert msg in str(exc_info.value)
@@ -552,7 +633,7 @@ def test_hamiltonian_evaluation():
     syst[new_hop[0]] = onsite_raises
     syst[new_hop] = hopping_raises
     fsyst = syst.finalized()
-    hop = tuple(map(fsyst.sites.index, new_hop))
+    hop = tuple(map(fsyst.id_by_site.__getitem__, new_hop))
     test_raising(fsyst, hop)
 
     # test with infinite system
@@ -560,17 +641,125 @@ def test_hamiltonian_evaluation():
     for k, v in it.chain(syst.site_value_pairs(), syst.hopping_value_pairs()):
         inf_syst[k] = v
     inf_fsyst = inf_syst.finalized()
-    hop = tuple(map(inf_fsyst.sites.index, new_hop))
+    hop = tuple(map(inf_fsyst.id_by_site.__getitem__, new_hop))
     test_raising(inf_fsyst, hop)
 
 
+def test_vectorized_hamiltonian_evaluation():
+
+    def onsite(site):
+        return site.tag[0]
+
+    def vectorized_onsite(sites):
+        return sites.tags[:, 0]
+
+    def hopping(to_site, from_site):
+        a, b = to_site.tag, from_site.tag
+        return a[0] + b[0] + 1j * (a[1] - b[1])
+
+    def vectorized_hopping(to_sites, from_sites):
+        a, b = to_sites.tags, from_sites.tags
+        return a[:, 0] + b[:, 0] + 1j * (a[:, 1] - b[:, 1])
+
+    tags = [(0, 0), (1, 1), (2, 2), (3, 3)]
+    edges = [(0, 1), (0, 2), (0, 3), (1, 2)]
+
+    fam = builder.SimpleSiteFamily(norbs=1)
+    sites = [fam(*tag) for tag in tags]
+    hops = [(fam(*tags[i]), fam(*tags[j])) for (i, j) in edges]
+
+    syst_simple = builder.Builder(vectorize=False)
+    syst_simple[sites] = onsite
+    syst_simple[hops] = hopping
+    fsyst_simple = syst_simple.finalized()
+
+    syst_vectorized = builder.Builder(vectorize=True)
+    syst_vectorized[sites] = vectorized_onsite
+    syst_vectorized[hops] = vectorized_hopping
+    fsyst_vectorized = syst_vectorized.finalized()
+
+    assert fsyst_vectorized.graph.num_nodes == len(tags)
+    assert fsyst_vectorized.graph.num_edges == 2 * len(edges)
+    assert len(fsyst_vectorized.site_arrays) == 1
+    assert fsyst_vectorized.site_arrays[0] == system.SiteArray(fam, tags)
+
+    assert np.allclose(
+        fsyst_simple.hamiltonian_submatrix(),
+        fsyst_vectorized.hamiltonian_submatrix(),
+    )
+
+    for i in range(len(tags)):
+        site = fsyst_vectorized.sites[i]
+        assert site in sites
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+            assert (
+                fsyst_vectorized.hamiltonian(i, i)
+                == fsyst_simple.hamiltonian(i, i))
+
+    for t, h in fsyst_vectorized.graph:
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+            assert (
+                fsyst_vectorized.hamiltonian(t, h)
+                == fsyst_simple.hamiltonian(t, h))
+
+    # Test infinite system, including hoppings that go both ways into
+    # the next cell
+    lat = kwant.lattice.square(norbs=1)
+
+    syst_vectorized = builder.Builder(kwant.TranslationalSymmetry((-1, 0)),
+                                      vectorize=True)
+    syst_vectorized[lat(0, 0)] = 4
+    syst_vectorized[lat(0, 1)] = 5
+    syst_vectorized[lat(0, 2)] = vectorized_onsite
+    syst_vectorized[(lat(1, 0), lat(0, 0))] = 1j
+    syst_vectorized[(lat(2, 1), lat(1, 1))] = vectorized_hopping
+    fsyst_vectorized = syst_vectorized.finalized()
+
+    syst_simple = builder.Builder(kwant.TranslationalSymmetry((-1, 0)),
+                                      vectorize=False)
+    syst_simple[lat(0, 0)] = 4
+    syst_simple[lat(0, 1)] = 5
+    syst_simple[lat(0, 2)] = onsite
+    syst_simple[(lat(1, 0), lat(0, 0))] = 1j
+    syst_simple[(lat(2, 1), lat(1, 1))] = hopping
+    fsyst_simple = syst_simple.finalized()
+
+    assert np.allclose(
+        fsyst_vectorized.hamiltonian_submatrix(),
+        fsyst_simple.hamiltonian_submatrix(),
+    )
+    assert np.allclose(
+        fsyst_vectorized.cell_hamiltonian(),
+        fsyst_simple.cell_hamiltonian(),
+    )
+    assert np.allclose(
+        fsyst_vectorized.inter_cell_hopping(),
+        fsyst_simple.inter_cell_hopping(),
+    )
+
+
+def test_vectorized_requires_norbs():
+
+    # Catch deprecation warning for lack of norbs
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore")
+        fam = builder.SimpleSiteFamily()
+
+    syst = builder.Builder(vectorize=True)
+    syst[fam(0, 0)] = 1
+
+    raises(ValueError, syst.finalized)
+
+
 def test_dangling():
     def make_system():
         #        1
         #       / \
         #    3-0---2-4-5  6-7  8
         syst = builder.Builder()
-        fam = builder.SimpleSiteFamily()
+        fam = builder.SimpleSiteFamily(norbs=1)
         syst[(fam(i) for i in range(9))] = None
         syst[[(fam(0), fam(1)), (fam(1), fam(2)), (fam(2), fam(0))]] = None
         syst[[(fam(0), fam(3)), (fam(2), fam(4)), (fam(4), fam(5))]] = None
@@ -596,7 +785,7 @@ def test_dangling():
 
 
 def test_builder_with_symmetry():
-    g = kwant.lattice.general(ta.identity(3))
+    g = kwant.lattice.general(ta.identity(3), norbs=1)
     sym = kwant.TranslationalSymmetry((0, 0, 3), (0, 2, 0))
     syst = builder.Builder(sym)
 
@@ -642,7 +831,7 @@ def test_builder_with_symmetry():
 
 
 def test_fill():
-    g = kwant.lattice.square()
+    g = kwant.lattice.square(norbs=1)
     sym_x = kwant.TranslationalSymmetry((-1, 0))
     sym_xy = kwant.TranslationalSymmetry((-1, 0), (0, 1))
 
@@ -658,7 +847,7 @@ def test_fill():
                        lambda pos: True),
                       (builder.NoSymmetry(),
                        lambda pos: ta.dot(pos, pos) < 17)]:
-        cubic = kwant.lattice.general(ta.identity(3))
+        cubic = kwant.lattice.general(ta.identity(3), norbs=1)
 
         # Make a weird system.
         orig = kwant.Builder(sym)
@@ -769,7 +958,7 @@ def test_fill():
     assert sorted(target.hoppings()) == sorted(should_be_syst.hoppings())
 
     ## test that 'fill' respects the symmetry of the target builder
-    lat = kwant.lattice.chain(a=1)
+    lat = kwant.lattice.chain(a=1, norbs=1)
     template = builder.Builder(kwant.TranslationalSymmetry((-1,)))
     template[lat(0)] = 2
     template[lat.neighbors()] = -1
@@ -796,7 +985,7 @@ def test_fill():
         target.fill(template, lambda x: True, lat(0))
 
     # Test for warning when one of the starting sites is outside the template
-    lat = kwant.lattice.square()
+    lat = kwant.lattice.square(norbs=1)
     template = builder.Builder(kwant.TranslationalSymmetry((-1, 0)))
     template[lat(0, 0)] = None
     template[lat.neighbors()] = None
@@ -811,7 +1000,7 @@ def test_fill_sticky():
     separately.
     """
     # Generate model template.
-    lat = kwant.lattice.kagome()
+    lat = kwant.lattice.kagome(norbs=1)
     template = kwant.Builder(kwant.TranslationalSymmetry(
         lat.vec((1, 0)), lat.vec((0, 1))))
     for i, sl in enumerate(lat.sublattices):
@@ -844,7 +1033,7 @@ def test_fill_sticky():
 
 def test_attach_lead():
     fam = builder.SimpleSiteFamily(norbs=1)
-    fam_noncommensurate = builder.SimpleSiteFamily(name='other')
+    fam_noncommensurate = builder.SimpleSiteFamily(name='other', norbs=1)
 
     syst = builder.Builder()
     syst[fam(1)] = 0
@@ -901,7 +1090,7 @@ def test_attach_lead():
 
 
 def test_attach_lead_incomplete_unit_cell():
-    lat = kwant.lattice.chain()
+    lat = kwant.lattice.chain(norbs=1)
     syst = kwant.Builder()
     lead = kwant.Builder(kwant.TranslationalSymmetry((2,)))
     syst[lat(1)] = lead[lat(0)] = lead[lat(1)] = 0
@@ -912,7 +1101,7 @@ def test_attach_lead_incomplete_unit_cell():
 def test_neighbors_not_in_single_domain():
     sr = builder.Builder()
     lead = builder.Builder(VerySimpleSymmetry(-1))
-    fam = builder.SimpleSiteFamily()
+    fam = builder.SimpleSiteFamily(norbs=1)
     sr[(fam(x, y) for x in range(3) for y in range(3) if x >= y)] = 0
     sr[builder.HoppingKind((1, 0), fam)] = 1
     sr[builder.HoppingKind((0, 1), fam)] = 1
@@ -935,7 +1124,7 @@ def test_closest():
     rng = ensure_rng(10)
     for sym_dim in range(1, 4):
         for space_dim in range(sym_dim, 4):
-            lat = kwant.lattice.general(ta.identity(space_dim))
+            lat = kwant.lattice.general(ta.identity(space_dim), norbs=1)
 
             # Choose random periods.
             while True:
@@ -967,7 +1156,7 @@ def test_closest():
 
 
 def test_update():
-    lat = builder.SimpleSiteFamily()
+    lat = builder.SimpleSiteFamily(norbs=1)
 
     syst = builder.Builder()
     syst[[lat(0,), lat(1,)]] = 1
@@ -1006,8 +1195,8 @@ def test_update():
 # ghgh    hhgh
 #
 def test_HoppingKind():
-    g = kwant.lattice.general(ta.identity(3), name='some_lattice')
-    h = kwant.lattice.general(ta.identity(3), name='another_lattice')
+    g = kwant.lattice.general(ta.identity(3), name='some_lattice', norbs=1)
+    h = kwant.lattice.general(ta.identity(3), name='another_lattice', norbs=1)
     sym = kwant.TranslationalSymmetry((0, 2, 0))
     syst = builder.Builder(sym)
     syst[((h if max(x, y, z) % 2 else g)(x, y, z)
@@ -1047,8 +1236,8 @@ def test_HoppingKind():
 
 
 def test_invalid_HoppingKind():
-    g = kwant.lattice.general(ta.identity(3))
-    h = kwant.lattice.general(np.identity(3)[:-1])  # 2D lattice in 3D
+    g = kwant.lattice.general(ta.identity(3), norbs=1)
+    h = kwant.lattice.general(np.identity(3)[:-1], norbs=1)  # 2D lattice in 3D
 
     delta = (1, 0, 0)
 
@@ -1062,7 +1251,7 @@ def test_invalid_HoppingKind():
 
 
 def test_ModesLead_and_SelfEnergyLead():
-    lat = builder.SimpleSiteFamily()
+    lat = builder.SimpleSiteFamily(norbs=1)
     hoppings = [builder.HoppingKind((1, 0), lat),
                 builder.HoppingKind((0, 1), lat)]
     rng = Random(123)
@@ -1139,7 +1328,7 @@ def test_ModesLead_and_SelfEnergyLead():
 
 
 def test_site_pickle():
-    site = kwant.lattice.square()(0, 0)
+    site = kwant.lattice.square(norbs=1)(0, 0)
     assert pickle.loads(pickle.dumps(site)) == site
 
 
@@ -1201,15 +1390,22 @@ def test_discrete_symmetries():
 # We need to keep testing 'args', but we don't want to see
 # all the deprecation warnings in the test logs
 @pytest.mark.filterwarnings("ignore:.*'args' parameter")
-def test_argument_passing():
-    chain = kwant.lattice.chain()
+@pytest.mark.parametrize("vectorize", [False, True])
+def test_argument_passing(vectorize):
+    chain = kwant.lattice.chain(norbs=1)
 
     # Test for passing parameters to hamiltonian matrix elements
     def onsite(site, p1, p2):
-        return p1 + p2
+        if vectorize:
+            return (p1 + p2) * np.ones(len(site))
+        else:
+            return p1 + p2
 
     def hopping(site1, site2, p1, p2):
-        return p1 - p2
+        if vectorize:
+            return (p1 - p2) * np.ones(len(site1))
+        else:
+            return p1 - p2
 
     def gen_fill_syst(onsite, hopping, syst):
         syst[(chain(i) for i in range(3))] = onsite
@@ -1218,8 +1414,9 @@ def test_argument_passing():
 
     fill_syst = ft.partial(gen_fill_syst, onsite, hopping)
 
-    syst = fill_syst(kwant.Builder())
-    inf_syst = fill_syst(kwant.Builder(kwant.TranslationalSymmetry((-3,))))
+    syst = fill_syst(kwant.Builder(vectorize=vectorize))
+    inf_syst = fill_syst(kwant.Builder(kwant.TranslationalSymmetry((-3,)),
+                                       vectorize=vectorize))
 
     tests = (
         syst.hamiltonian_submatrix,
@@ -1235,28 +1432,34 @@ def test_argument_passing():
 
     # test that mixing 'args' and 'params' raises TypeError
     with raises(TypeError):
-        syst.hamiltonian(0, 0, *(2, 1), params=dict(p1=2, p2=1))
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+            syst.hamiltonian(0, 0, *(2, 1), params=dict(p1=2, p2=1))
+
     with raises(TypeError):
-        inf_syst.hamiltonian(0, 0, *(2, 1), params=dict(p1=2, p2=1))
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+            inf_syst.hamiltonian(0, 0, *(2, 1), params=dict(p1=2, p2=1))
 
     # Missing parameters raises TypeError
     with raises(TypeError):
-        syst.hamiltonian(0, 0, params=dict(p1=2))
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+            syst.hamiltonian(0, 0, params=dict(p1=2))
+
     with raises(TypeError):
-        syst.hamiltonian_submatrix(params=dict(p1=2))
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", category=KwantDeprecationWarning)
+            syst.hamiltonian_submatrix(params=dict(p1=2))
 
     # test that passing parameters without default values works, and that
     # passing parameters with default values fails
-    def onsite(site, p1, p2):
-        return p1 + p2
-
-    def hopping(site, site2, p1, p2):
-        return p1 - p2
 
     fill_syst = ft.partial(gen_fill_syst, onsite, hopping)
 
-    syst = fill_syst(kwant.Builder())
-    inf_syst = fill_syst(kwant.Builder(kwant.TranslationalSymmetry((-3,))))
+    syst = fill_syst(kwant.Builder(vectorize=vectorize))
+    inf_syst = fill_syst(kwant.Builder(kwant.TranslationalSymmetry((-3,)),
+                                       vectorize=vectorize))
 
     tests = (
         syst.hamiltonian_submatrix,
@@ -1272,12 +1475,18 @@ def test_argument_passing():
 
     # Some common, some different args for value functions
     def onsite2(site, a, b):
-        return site.pos + a + b
+        if vectorize:
+            return site.positions()[:, 0] + a + b
+        else:
+            return site.pos[0] + a + b
 
     def hopping2(site1, site2, a, c, b):
-        return a + b + c
+        if vectorize:
+            return (a + b + c) * np.ones(len(site1))
+        else:
+            return a + b + c
 
-    syst = kwant.Builder()
+    syst = kwant.Builder(vectorize=vectorize)
     syst[(chain(i) for i in range(3))] = onsite2
     syst[((chain(i), chain(i + 1)) for i in range(2))] = hopping2
     fsyst = syst.finalized()
@@ -1336,7 +1545,7 @@ def test_subs():
         salt = str(b) + str(c)
         return kwant.digest.uniform(ta.array((sitea.tag, siteb.tag)), salt=salt)
 
-    lat = kwant.lattice.chain()
+    lat = kwant.lattice.chain(norbs=1)
 
     def make_system(sym=kwant.builder.NoSymmetry(), n=3):
         syst = kwant.Builder(sym)
@@ -1388,8 +1597,9 @@ def test_subs():
     lead = lead.finalized()
     assert lead.parameters == {'lead_a', 'lead_b', 'lead_c'}
 
+
 def test_attach_stores_padding():
-    lat = kwant.lattice.chain()
+    lat = kwant.lattice.chain(norbs=1)
     syst = kwant.Builder()
     syst[lat(0)] = 0
     lead = kwant.Builder(kwant.TranslationalSymmetry(lat.prim_vecs[0]))
@@ -1400,7 +1610,7 @@ def test_attach_stores_padding():
 
 
 def test_finalization_preserves_padding():
-    lat = kwant.lattice.chain()
+    lat = kwant.lattice.chain(norbs=1)
     syst = kwant.Builder()
     for i in range(10):
         syst[lat(i)] = 0
@@ -1416,3 +1626,28 @@ def test_finalization_preserves_padding():
     syst = syst.finalized()
     # The order is guaranteed because the paddings are sorted.
     assert [syst.sites[i] for i in syst.lead_paddings[0]] == padding[:-1]
+
+
+def test_add_peierls_phase():
+
+    lat = kwant.lattice.square(norbs=1)
+    syst = kwant.Builder()
+    syst[(lat(i, j) for i in range(5) for j in range(5))] = 4
+    syst[lat.neighbors()] = lambda a, b, t: -t
+
+    lead = kwant.Builder(kwant.TranslationalSymmetry((-1, 0)))
+    lead[(lat(0, j) for j in range(5))] = 4
+    lead[lat.neighbors()] = -1
+
+    syst.attach_lead(lead)
+    syst.attach_lead(lead.reversed())
+
+    syst, phase = builder.add_peierls_phase(syst)
+
+    assert isinstance(syst, builder.FiniteSystem)
+
+    params = phase(1, 0, 0)
+
+    assert all(p in params for p in ('phi', 'phi_lead0', 'phi_lead1'))
+
+    kwant.smatrix(syst, energy=0.1, params=dict(t=-1, **params))

kwant/tests/test_comprehensive.py

@@ -18,7 +18,7 @@ def test_qhe(W=16, L=8):
         x, y = pos
         return -L < x < L and abs(y) < W - 5.5 * math.exp(-x**2 / 5**2)
 
-    lat = kwant.lattice.square()
+    lat = kwant.lattice.square(norbs=1)
     syst = kwant.Builder()
 
     syst[lat.shape(central_region, (0, 0))] = onsite

kwant/tests/test_lattice.py

@@ -6,6 +6,7 @@
 # the file AUTHORS.rst at the top-level directory of this distribution and at
 # http://kwant-project.org/authors.
 
+import warnings
 from math import sqrt
 import numpy as np
 import tinyarray as ta
@@ -17,40 +18,42 @@ import pytest
 
 def test_closest():
     rng = ensure_rng(4)
-    lat = lattice.general(((1, 0), (0.5, sqrt(3)/2)))
+    lat = lattice.general(((1, 0), (0.5, sqrt(3)/2)), norbs=1)
     for i in range(50):
         point = 20 * rng.random_sample(2)
         closest = lat(*lat.closest(point)).pos
         assert np.linalg.norm(point - closest) <= 1 / sqrt(3)
-    lat = lattice.general(rng.randn(3, 3))
+    lat = lattice.general(rng.randn(3, 3), norbs=1)
     for i in range(50):
         tag = rng.randint(10, size=(3,))
         assert lat.closest(lat(*tag).pos) == tag
 
 
 def test_general():
-    for lat in (lattice.general(((1, 0), (0.5, 0.5))),
+    for lat in (lattice.general(((1, 0), (0.5, 0.5)), norbs=1),
                 lattice.general(((1, 0), (0.5, sqrt(3)/2)),
-                                     ((0, 0), (0, 1/sqrt(3))))):
+                                ((0, 0), (0, 1/sqrt(3))),
+                                norbs=1,
+                               )):
         for sl in lat.sublattices:
             tag = (-5, 33)
             site = sl(*tag)
             assert tag == sl.closest(site.pos)
 
     # Test 2D lattice with 1 vector.
-    lat = lattice.general([[1, 0]])
+    lat = lattice.general([[1, 0]], norbs=1)
     site = lat(0)
     raises(ValueError, lat, 0, 1)
 
 
 def test_neighbors():
-    lat = lattice.honeycomb(1e-10)
+    lat = lattice.honeycomb(1e-10, norbs=1)
     num_nth_nearest = [len(lat.neighbors(n)) for n in range(5)]
     assert num_nth_nearest == [2, 3, 6, 3, 6]
-    lat = lattice.general([(0, 1e8, 0, 0), (0, 0, 1e8, 0)])
+    lat = lattice.general([(0, 1e8, 0, 0), (0, 0, 1e8, 0)], norbs=1)
     num_nth_nearest = [len(lat.neighbors(n)) for n in range(5)]
     assert num_nth_nearest == [1, 2, 2, 2, 4]
-    lat = lattice.chain(1e-10)
+    lat = lattice.chain(1e-10, norbs=1)
     num_nth_nearest = [len(lat.neighbors(n)) for n in range(5)]
     assert num_nth_nearest == 5 * [1]
 
@@ -59,7 +62,7 @@ def test_shape():
     def in_circle(pos):
         return pos[0] ** 2 + pos[1] ** 2 < 3
 
-    lat = lattice.honeycomb()
+    lat = lattice.honeycomb(norbs=1)
     sites = list(lat.shape(in_circle, (0, 0))())
     sites_alt = list()
     sl0, sl1 = lat.sublattices
@@ -88,7 +91,7 @@ def test_wire():
     vecs = rng.randn(3, 3)
     vecs[0] = [1, 0, 0]
     center = rng.randn(3)
-    lat = lattice.general(vecs, rng.randn(4, 3))
+    lat = lattice.general(vecs, rng.randn(4, 3), norbs=1)
     syst = builder.Builder(lattice.TranslationalSymmetry((2, 0, 0)))
     def wire_shape(pos):
         pos = np.array(pos)
@@ -103,8 +106,8 @@ def test_wire():
 
 def test_translational_symmetry():
     ts = lattice.TranslationalSymmetry
-    f2 = lattice.general(np.identity(2))
-    f3 = lattice.general(np.identity(3))
+    f2 = lattice.general(np.identity(2), norbs=1)
+    f3 = lattice.general(np.identity(3), norbs=1)
     shifted = lambda site, delta: site.family(*ta.add(site.tag, delta))
 
     raises(ValueError, ts, (0, 0, 4), (0, 5, 0), (0, 0, 2))
@@ -112,7 +115,7 @@ def test_translational_symmetry():
     raises(ValueError, sym.add_site_family, f2)
 
     # Test lattices with dimension smaller than dimension of space.
-    f2in3 = lattice.general([[4, 4, 0], [4, -4, 0]])
+    f2in3 = lattice.general([[4, 4, 0], [4, -4, 0]], norbs=1)
     sym = ts((8, 0, 0))
     sym.add_site_family(f2in3)
     sym = ts((8, 0, 1))
@@ -150,7 +153,7 @@ def test_translational_symmetry():
                         (site, shifted(site, hop)))
 
     # Test act for hoppings belonging to different lattices.
-    f2p = lattice.general(2 * np.identity(2))
+    f2p = lattice.general(2 * np.identity(2), norbs=1)
     sym = ts(*(2 * np.identity(2)))
     assert sym.act((1, 1), f2(0, 0), f2p(0, 0)) == (f2(2, 2), f2p(1, 1))
     assert sym.act((1, 1), f2p(0, 0), f2(0, 0)) == (f2p(1, 1), f2(2, 2))
@@ -160,7 +163,7 @@ def test_translational_symmetry():
     # generated symmetry with proper vectors.
     rng = ensure_rng(30)
     vec = rng.randn(3, 5)
-    lat = lattice.general(vec)
+    lat = lattice.general(vec, norbs=1)
     total = 0
     for k in range(1, 4):
         for i in range(10):
@@ -176,7 +179,7 @@ def test_translational_symmetry():
 
 def test_translational_symmetry_reversed():
     rng = ensure_rng(30)
-    lat = lattice.general(np.identity(3))
+    lat = lattice.general(np.identity(3), norbs=1)
     sites = [lat(i, j, k) for i in range(-2, 6) for j in range(-2, 6)
                           for k in range(-2, 6)]
     for i in range(4):
@@ -194,9 +197,9 @@ def test_translational_symmetry_reversed():
 
 
 def test_monatomic_lattice():
-    lat = lattice.square()
-    lat2 = lattice.general(np.identity(2))
-    lat3 = lattice.square(name='no')
+    lat = lattice.square(norbs=1)
+    lat2 = lattice.general(np.identity(2), norbs=1)
+    lat3 = lattice.square(name='no', norbs=1)
     assert len(set([lat, lat2, lat3, lat(0, 0), lat2(0, 0), lat3(0, 0)])) == 4
 
 @pytest.mark.parametrize('prim_vecs, basis', [
@@ -210,16 +213,22 @@ def test_monatomic_lattice():
 ])
 def test_lattice_constraints(prim_vecs, basis):
     with pytest.raises(ValueError):
-        lattice.general(prim_vecs, basis)
+        lattice.general(prim_vecs, basis, norbs=1)
 
 
 def test_norbs():
     id_mat = np.identity(2)
     # Monatomic lattices
-    assert lattice.general(id_mat).norbs == None
+    # Catch deprecation warning
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore")
+        assert lattice.general(id_mat).norbs == None
     assert lattice.general(id_mat, norbs=2).norbs == 2
     # Polyatomic lattices
-    lat = lattice.general(id_mat, basis=id_mat, norbs=None)
+    # Catch deprecation warning
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore")
+        lat = lattice.general(id_mat, basis=id_mat, norbs=None)
     for l in lat.sublattices:
         assert l.norbs == None
     lat = lattice.general(id_mat, basis=id_mat, norbs=2)
@@ -237,8 +246,14 @@ def test_norbs():
     raises(ValueError, lattice.general, id_mat, norbs=1.5)
     raises(ValueError, lattice.general, id_mat, id_mat, norbs=1.5)
     raises(ValueError, lattice.general, id_mat, id_mat, norbs=[1.5, 1.5])
+    # should raise ValueError if norbs is <= 0
+    raises(ValueError, lattice.general, id_mat, norbs=0)
+    raises(ValueError, lattice.general, id_mat, norbs=-1)
     # test that lattices with different norbs are compared `not equal`
-    lat = lattice.general(id_mat, basis=id_mat, norbs=None)
+    # Catch deprecation warning
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore")
+        lat = lattice.general(id_mat, basis=id_mat, norbs=None)
     lat1 = lattice.general(id_mat, basis=id_mat, norbs=1)
     lat2 = lattice.general(id_mat, basis=id_mat, norbs=2)
     assert lat != lat1
@@ -247,7 +262,7 @@ def test_norbs():
 
 
 def test_symmetry_act():
-    lat = lattice.square()
+    lat = lattice.square(norbs=1)
     sym = lattice.TranslationalSymmetry((1, 0), (0, 1))
     site = lat(0, 0)
     hopping = (lat(0, 0), lat(1, 0))

kwant/tests/test_operator.py

@@ -6,6 +6,7 @@
 # the file AUTHORS.rst at the top-level directory of this distribution and at
 # http://kwant-project.org/authors.
 
+import warnings
 import functools as ft
 from collections import deque
 import pickle
@@ -59,7 +60,10 @@ def test_operator_construction():
     N = len(fsyst.sites)
 
     # test construction failure if norbs not given
-    latnone = kwant.lattice.chain()
+    # Catch deprecation warning
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore")
+        latnone = kwant.lattice.chain()
     syst[latnone(0)] = 1
     for A in opservables:
         raises(ValueError, A, syst.finalized())
@@ -128,12 +132,35 @@ def test_operator_construction():
     fwhere = tuple(fsyst.id_by_site[s] for s in where)
     A = ops.Density(fsyst, where=where)
     assert np.all(np.asarray(A.where).reshape(-1) == fwhere)
+    # Test for passing integers as 'where'
+    A = ops.Density(fsyst, where=fwhere)
+    assert np.all(np.asarray(A.where).reshape(-1) == fwhere)
+    # Test passing invalid sites
+    with raises(ValueError):
+        ops.Density(fsyst, where=[lat(100)])
+    with raises(ValueError):
+        ops.Density(fsyst, where=[-1])
+    with raises(ValueError):
+        ops.Density(fsyst, where=[10000])
 
     where = [(lat(2, 2), lat(1, 2)), (lat(0, 0), lat(0, 1))]
     fwhere = np.asarray([(fsyst.id_by_site[a], fsyst.id_by_site[b])
               for a, b in where])
     A = ops.Current(fsyst, where=where)
     assert np.all(np.asarray(A.where) == fwhere)
+    # Test for passing integers as 'where'
+    A = ops.Current(fsyst, where=fwhere)
+    assert np.all(np.asarray(A.where) == fwhere)
+    # Test passing invalid hoppings
+    with raises(ValueError):
+        ops.Current(fsyst, where=[(lat(2, 2), lat(0, 0))])
+    with raises(ValueError):
+        ops.Current(fsyst, where=[(-1, 1)])
+    with raises(ValueError):
+        ops.Current(fsyst, where=[(len(fsyst.sites), 1)])
+    with raises(ValueError):
+        ops.Current(fsyst, where=[(fsyst.id_by_site[lat(2, 2)],
+                                   fsyst.id_by_site[lat(0, 0)])])
 
     # test construction with `where` given by a function
     tag_list = [(1, 0), (1, 1), (1, 2)]
@@ -304,7 +331,7 @@ def test_opservables_spin():
     down, up = kwant.wave_function(fsyst, energy=1., params=params)(0)
 
     x_hoppings = kwant.builder.HoppingKind((1,), lat)
-    spin_current_z = ops.Current(fsyst, sigmaz, where=x_hoppings(syst))
+    spin_current_z = ops.Current(fsyst, sigmaz, where=list(x_hoppings(syst)))
     _test(spin_current_z, up, params=params, per_el_val=1)
     _test(spin_current_z, down, params=params, per_el_val=-1)
 
@@ -366,12 +393,14 @@ def test_opservables_gauged():
                          (Us[i], sigmaz, Us[i].conjugate().transpose()))
 
     x_hoppings = kwant.builder.HoppingKind((1,), lat)
-    spin_current_gauge = ops.Current(fsyst, M_a, where=x_hoppings(syst))
+    spin_current_gauge = ops.Current(fsyst, M_a,
+                                     where=list(x_hoppings(syst)))
     _test(spin_current_gauge, up, per_el_val=1)
     _test(spin_current_gauge, down, per_el_val=-1)
     # check the reverse is also true
     minus_x_hoppings = kwant.builder.HoppingKind((-1,), lat)
-    spin_current_gauge = ops.Current(fsyst, M_a, where=minus_x_hoppings(syst))
+    spin_current_gauge = ops.Current(fsyst, M_a,
+                                     where=list(minus_x_hoppings(syst)))
     _test(spin_current_gauge, up, per_el_val=-1)
     _test(spin_current_gauge, down, per_el_val=1)
 
@@ -416,7 +445,7 @@ def test_arg_passing(A):
     lat1 = kwant.lattice.chain(norbs=1)
 
     syst = kwant.Builder()
-    syst[lat1(0)] = syst[lat1(1)] = lambda s0, a, b: s0.pos + a + b
+    syst[lat1(0)] = syst[lat1(1)] = lambda s0, a, b: s0.pos[0] + a + b
     syst[lat1.neighbors()] = lambda s0, s1, a, b: a - b
     fsyst = syst.finalized()
 

kwant/tests/test_plotter.py

@@ -91,7 +91,7 @@ def syst_2d(W=3, r1=3, r2=8):
 
 
 def syst_3d(W=3, r1=2, r2=4, a=1, t=1.0):
-    lat = kwant.lattice.general(((a, 0, 0), (0, a, 0), (0, 0, a)))
+    lat = kwant.lattice.general(((a, 0, 0), (0, a, 0), (0, 0, a)), norbs=1)
     syst = kwant.Builder()
 
     def ring(pos):
@@ -162,13 +162,29 @@ def test_plot_more_site_families_than_colors():
     # https://gitlab.kwant-project.org/kwant/kwant/issues/257
     ncolors = len(pyplot.rcParams['axes.prop_cycle'])
     syst = kwant.Builder()
-    lattices = [kwant.lattice.square(name=i) for i in range(ncolors + 1)]
+    lattices = [kwant.lattice.square(name=i, norbs=1)
+                for i in range(ncolors + 1)]
     for i, lat in enumerate(lattices):
         syst[lat(i, 0)] = None
     with tempfile.TemporaryFile('w+b') as out:
         plotter.plot(syst, file=out)
 
 
+@pytest.mark.skipif(not _plotter.mpl_available, reason="Matplotlib unavailable.")
+def test_plot_raises_on_bad_site_spec():
+    syst = kwant.Builder()
+    lat = kwant.lattice.square(norbs=1)
+    syst[(lat(i, j) for i in range(5) for j in range(5))] = None
+
+    # Cannot provide site_size as an array when syst is a Builder
+    with pytest.raises(TypeError):
+        plotter.plot(syst, site_size=[1] * 25)
+
+    # Cannot provide site_size as an array when syst is a Builder
+    with pytest.raises(TypeError):
+        plotter.plot(syst, site_symbol=['o'] * 25)
+
+
 def good_transform(pos):
     x, y = pos
     return y, x
@@ -237,7 +253,7 @@ def test_spectrum():
     def ham_2d(a, b, c):
         return np.eye(2) * (a**2 + b**2 + c**2)
 
-    lat = kwant.lattice.chain()
+    lat = kwant.lattice.chain(norbs=1)
     syst = kwant.Builder()
     syst[(lat(i) for i in range(3))] = lambda site, a, b: a + b
     syst[lat.neighbors()] = lambda site1, site2, c: c
@@ -361,7 +377,7 @@ def _border_is_0(field):
 def _test_border_0(interpolator):
     ## Test that current is always identically zero at box boundaries
     syst = kwant.Builder()
-    lat = kwant.lattice.square()
+    lat = kwant.lattice.square(norbs=1)
     syst[[lat(0, 0), lat(1, 0)]] = None
     syst[(lat(0, 0), lat(1, 0))] = None
     syst = syst.finalized()
@@ -488,7 +504,7 @@ def test_current_interpolation():
 
     ### Tests on a divergence-free current (closed system)
 
-    lat = kwant.lattice.general([(1, 0), (0.5, np.sqrt(3) / 2)])
+    lat = kwant.lattice.general([(1, 0), (0.5, np.sqrt(3) / 2)], norbs=1)
     syst = kwant.Builder()
     sites = [lat(0, 0), lat(1, 0), lat(0, 1), lat(2, 2)]
     syst[sites] = None

kwant/tests/test_system.py

-# Copyright 2011-2016 Kwant authors.
+# Copyright 2011-2019 Kwant authors.
 #
 # This file is part of Kwant.  It is subject to the license terms in the file
 # LICENSE.rst found in the top-level directory of this distribution and at
@@ -8,6 +8,7 @@
 
 import pickle
 import copy
+import pytest
 from pytest import raises
 import numpy as np
 from scipy import sparse
@@ -15,9 +16,11 @@ import kwant
 from kwant._common import ensure_rng
 
 
-def test_hamiltonian_submatrix():
-    syst = kwant.Builder()
-    chain = kwant.lattice.chain()
+@pytest.mark.parametrize("vectorize", [False, True])
+def test_hamiltonian_submatrix(vectorize):
+    syst = kwant.Builder(vectorize=vectorize)
+    chain = kwant.lattice.chain(norbs=1)
+    chain2 = kwant.lattice.chain(norbs=2)
     for i in range(3):
         syst[chain(i)] = 0.5 * i
     for i in range(2):
@@ -27,7 +30,11 @@ def test_hamiltonian_submatrix():
     mat = syst2.hamiltonian_submatrix()
     assert mat.shape == (3, 3)
     # Sorting is required due to unknown compression order of builder.
-    perm = np.argsort([os[0] for os in syst2.onsites])
+    if vectorize:
+        _, (site_offsets, _) = syst2.subgraphs[0]
+    else:
+        site_offsets = [os[0] for os in syst2.onsites]
+    perm = np.argsort(site_offsets)
     mat_should_be = np.array([[0, 1j, 0], [-1j, 0.5, 2j], [0, -2j, 1]])
 
     mat = mat[perm, :]
@@ -41,19 +48,12 @@ def test_hamiltonian_submatrix():
     mat = mat[:, perm]
     np.testing.assert_array_equal(mat, mat_should_be)
 
-    mat = syst2.hamiltonian_submatrix((), perm[[0, 1]], perm[[2]])
-    np.testing.assert_array_equal(mat, mat_should_be[:2, 2:3])
-
-    mat = syst2.hamiltonian_submatrix((), perm[[0, 1]], perm[[2]], sparse=True)
-    mat = mat.toarray()
-    np.testing.assert_array_equal(mat, mat_should_be[:2, 2:3])
-
     # Test for correct treatment of matrix input.
-    syst = kwant.Builder()
-    syst[chain(0)] = np.array([[0, 1j], [-1j, 0]])
+    syst = kwant.Builder(vectorize=vectorize)
+    syst[chain2(0)] = np.array([[0, 1j], [-1j, 0]])
     syst[chain(1)] = np.array([[1]])
     syst[chain(2)] = np.array([[2]])
-    syst[chain(1), chain(0)] = np.array([[1, 2j]])
+    syst[chain(1), chain2(0)] = np.array([[1, 2j]])
     syst[chain(2), chain(1)] = np.array([[3j]])
     syst2 = syst.finalized()
     mat_dense = syst2.hamiltonian_submatrix()
@@ -62,9 +62,10 @@ def test_hamiltonian_submatrix():
 
     # Test precalculation of modes.
     rng = ensure_rng(5)
-    lead = kwant.Builder(kwant.TranslationalSymmetry((-1,)))
-    lead[chain(0)] = np.zeros((2, 2))
-    lead[chain(0), chain(1)] = rng.randn(2, 2)
+    lead = kwant.Builder(kwant.TranslationalSymmetry((-1,)),
+                         vectorize=vectorize)
+    lead[chain2(0)] = np.zeros((2, 2))
+    lead[chain2(0), chain2(1)] = rng.randn(2, 2)
     syst.attach_lead(lead)
     syst2 = syst.finalized()
     smatrix = kwant.smatrix(syst2, .1).data
@@ -74,20 +75,27 @@ def test_hamiltonian_submatrix():
     raises(ValueError, kwant.solvers.default.greens_function, syst3, 0.2)
 
     # Test for shape errors.
-    syst[chain(0), chain(2)] = np.array([[1, 2]])
+    syst[chain2(0), chain(2)] = np.array([[1, 2]])
     syst2 = syst.finalized()
     raises(ValueError, syst2.hamiltonian_submatrix)
     raises(ValueError, syst2.hamiltonian_submatrix, sparse=True)
-    syst[chain(0), chain(2)] = 1
+    syst[chain2(0), chain(2)] = 1
     syst2 = syst.finalized()
     raises(ValueError, syst2.hamiltonian_submatrix)
     raises(ValueError, syst2.hamiltonian_submatrix, sparse=True)
+    if vectorize:  # non-vectorized systems don't check this at finalization
+        # Add another hopping of the same type but with a different
+        # (and still incompatible) shape.
+        syst[chain2(0), chain(1)] = np.array([[1, 2]])
+        raises(ValueError, syst.finalized)
 
 
-def test_pickling():
-    syst = kwant.Builder()
-    lead = kwant.Builder(symmetry=kwant.TranslationalSymmetry([1.]))
-    lat = kwant.lattice.chain()
+@pytest.mark.parametrize("vectorize", [False, True])
+def test_pickling(vectorize):
+    syst = kwant.Builder(vectorize=vectorize)
+    lead = kwant.Builder(symmetry=kwant.TranslationalSymmetry([1.]),
+                         vectorize=vectorize)
+    lat = kwant.lattice.chain(norbs=1)
     syst[lat(0)] = syst[lat(1)] = 0
     syst[lat(0), lat(1)] = 1
     lead[lat(0)] = syst[lat(1)] = 0

kwant/tests/test_wraparound.py

@@ -37,7 +37,8 @@ def _simple_syst(lat, E=0, t=1+1j, sym=None):
 
 def test_consistence_with_bands(kx=1.9, nkys=31):
     kys = np.linspace(-np.pi, np.pi, nkys)
-    for lat in [kwant.lattice.honeycomb(), kwant.lattice.square()]:
+    for lat in [kwant.lattice.honeycomb(norbs=1),
+                kwant.lattice.square(norbs=1)]:
         syst = _simple_syst(lat)
         wa_keep_1 = wraparound(syst, keep=1).finalized()
         wa_keep_none = wraparound(syst).finalized()
@@ -56,7 +57,7 @@ def test_consistence_with_bands(kx=1.9, nkys=31):
 
 
 def test_opposite_hoppings():
-    lat = kwant.lattice.square()
+    lat = kwant.lattice.square(norbs=1)
 
     for val in [1j, lambda a, b: 1j]:
         syst = kwant.Builder(kwant.TranslationalSymmetry((1, 1)))
@@ -74,7 +75,8 @@ def test_opposite_hoppings():
 def test_value_types(k=(-1.1, 0.5), E=2, t=1):
     k = dict(zip(('k_x', 'k_y', 'k_z'), k))
     sym_extents = [1, 2, 3]
-    lattices = [kwant.lattice.honeycomb(), kwant.lattice.square()]
+    lattices = [kwant.lattice.honeycomb(norbs=1),
+                kwant.lattice.square(norbs=1)]
     lat_syms = [
         (lat, kwant.TranslationalSymmetry(lat.vec((n, 0)), lat.vec((0, n))))
         for n, lat in itertools.product(sym_extents, lattices)
@@ -112,7 +114,7 @@ def test_value_types(k=(-1.1, 0.5), E=2, t=1):
 
 
 def test_signatures():
-    lat = kwant.lattice.square()
+    lat = kwant.lattice.square(norbs=1)
     syst = kwant.Builder(kwant.TranslationalSymmetry((-3, 0), (0, 1)))
     # onsites and hoppings that will be bound as sites
     syst[lat(-2, 0)] = 4
@@ -162,7 +164,7 @@ def test_signatures():
 
 
 def test_symmetry():
-    syst = _simple_syst(kwant.lattice.square())
+    syst = _simple_syst(kwant.lattice.square(norbs=1))
 
     matrices = [np.random.rand(2, 2) for i in range(4)]
     laws = (matrices, [(lambda a: m) for m in matrices])
@@ -190,10 +192,10 @@ def test_symmetry():
 
 @pytest.mark.skipif(not _plotter.mpl_available, reason="Matplotlib unavailable.")
 def test_plot_2d_bands():
-    chain = kwant.lattice.chain()
-    square = kwant.lattice.square()
-    cube = kwant.lattice.general([(1, 0, 0), (0, 1, 0), (0, 0, 1)])
-    hc = kwant.lattice.honeycomb()
+    chain = kwant.lattice.chain(norbs=1)
+    square = kwant.lattice.square(norbs=1)
+    cube = kwant.lattice.general([(1, 0, 0), (0, 1, 0), (0, 0, 1)], norbs=1)
+    hc = kwant.lattice.honeycomb(norbs=1)
 
     syst_1d = kwant.Builder(kwant.TranslationalSymmetry(*chain._prim_vecs))
     syst_1d[chain(0)] = 2
@@ -245,7 +247,7 @@ def test_fd_mismatch():
     # around in all directions, but could not be wrapped around when 'keep' is
     # provided.
     sqrt3 = np.sqrt(3)
-    lat = kwant.lattice.general([(sqrt3, 0), (-sqrt3/2, 1.5)])
+    lat = kwant.lattice.general([(sqrt3, 0), (-sqrt3/2, 1.5)], norbs=1)
     T = kwant.TranslationalSymmetry((sqrt3, 0), (0, 3))
 
     syst1 = kwant.Builder(T)
@@ -269,7 +271,8 @@ def test_fd_mismatch():
     ## Test that spectrum of non-trivial system (including above cases)
     ## is the same, regardless of the way in which it is wrapped around
     lat = kwant.lattice.general([(sqrt3, 0), (-sqrt3/2, 1.5)],
-                                [(sqrt3 / 2, 0.5), (0, 1)])
+                                [(sqrt3 / 2, 0.5), (0, 1)],
+                                norbs=1)
     a, b = lat.sublattices
     T = kwant.TranslationalSymmetry((3 * sqrt3, 0), (0, 3))
     syst = kwant.Builder(T)
@@ -302,7 +305,7 @@ def test_fd_mismatch():
     assert all(np.allclose(E, E[0]) for E in E_k)
 
     # Test square lattice with oblique unit cell
-    lat = kwant.lattice.general(np.eye(2))
+    lat = kwant.lattice.general(np.eye(2), norbs=1)
     translations = kwant.lattice.TranslationalSymmetry([2, 2], [0, 2])
     syst = kwant.Builder(symmetry=translations)
     syst[lat.shape(lambda site: True, [0, 0])] = 1
@@ -314,7 +317,7 @@ def test_fd_mismatch():
 
     # Test Rocksalt structure
     # cubic lattice that contains both sublattices
-    lat = kwant.lattice.general(np.eye(3))
+    lat = kwant.lattice.general(np.eye(3), norbs=1)
     # Builder with FCC translational symmetries.
     translations = kwant.lattice.TranslationalSymmetry([1, 1, 0], [1, 0, 1], [0, 1, 1])
     syst = kwant.Builder(symmetry=translations)
@@ -341,7 +344,7 @@ def test_fd_mismatch():
     def shape(site):
         return abs(site.tag[2]) < 4
 
-    lat = kwant.lattice.general(np.eye(3))
+    lat = kwant.lattice.general(np.eye(3), norbs=1)
     # First choice: primitive UC
     translations = kwant.lattice.TranslationalSymmetry([1, 1, 0], [1, -1, 0], [1, 0, 1])
     syst = kwant.Builder(symmetry=translations)

kwant/wraparound.py

@@ -20,36 +20,12 @@ from . import builder, system, plotter
 from .linalg import lll
 from .builder import herm_conj, HermConjOfFunc
 from .lattice import TranslationalSymmetry
-from ._common import get_parameters
+from ._common import get_parameters, memoize
 
 
 __all__ = ['wraparound', 'plot_2d_bands']
 
 
-def _hashable(obj):
-    return isinstance(obj, collections.abc.Hashable)
-
-
-def _memoize(f):
-    """Decorator to memoize a function that works even with unhashable args.
-
-    This decorator will even work with functions whose args are not hashable.
-    The cache key is made up by the hashable arguments and the ids of the
-    non-hashable args.  It is up to the user to make sure that non-hashable
-    args do not change during the lifetime of the decorator.
-
-    This decorator will keep reevaluating functions that return None.
-    """
-    def lookup(*args):
-        key = tuple(arg if _hashable(arg) else id(arg) for arg in args)
-        result = cache.get(key)
-        if result is None:
-            cache[key] = result = f(*args)
-        return result
-    cache = {}
-    return lookup
-
-
 def _set_signature(func, params):
     """Set the signature of 'func'.
 
@@ -103,7 +79,7 @@ def wraparound(builder, keep=None, *, coordinate_names='xyz'):
     format. It will be deprecated in the 2.0 release of Kwant.
     """
 
-    @_memoize
+    @memoize
     def bind_site(val):
         def f(*args):
             a, *args = args
@@ -113,7 +89,7 @@ def wraparound(builder, keep=None, *, coordinate_names='xyz'):
         _set_signature(f, get_parameters(val) + momenta)
         return f
 
-    @_memoize
+    @memoize
     def bind_hopping_as_site(elem, val):
         def f(*args):
             a, *args = args
@@ -128,7 +104,7 @@ def wraparound(builder, keep=None, *, coordinate_names='xyz'):
         _set_signature(f, params + momenta)
         return f
 
-    @_memoize
+    @memoize
     def bind_hopping(elem, val):
         def f(*args):
             a, b, *args = args
@@ -142,7 +118,7 @@ def wraparound(builder, keep=None, *, coordinate_names='xyz'):
         _set_signature(f, params + momenta)
         return f
 
-    @_memoize
+    @memoize
     def bind_sum(num_sites, *vals):
         """Construct joint signature for all 'vals'."""
 
@@ -207,6 +183,9 @@ def wraparound(builder, keep=None, *, coordinate_names='xyz'):
         f.__signature__ = inspect.Signature(params.values())
         return f
 
+    if builder.vectorize:
+        raise TypeError("'wraparound' does not work with vectorized Builders.")
+
     try:
         momenta = ['k_{}'.format(coordinate_names[i])
                    for i in range(len(builder.symmetry.periods))]
@@ -386,10 +365,14 @@ def plot_2d_bands(syst, k_x=31, k_y=31, params=None,
     if not hasattr(syst, '_wrapped_symmetry'):
         raise TypeError("Expecting a system that was produced by "
                         "'kwant.wraparound.wraparound'.")
-    if not isinstance(syst, system.FiniteSystem):
+    if isinstance(syst, system.InfiniteSystem):
         msg = ("All symmetry directions must be wrapped around: specify "
                "'keep=None' when calling 'kwant.wraparound.wraparound'.")
         raise TypeError(msg)
+    if isinstance(syst, builder.Builder):
+        msg = ("Expecting a finalized system: remember to finalize your "
+               "system with 'syst.finalized()'.")
+        raise TypeError(msg)
 
     params = params or {}
     lat_ndim, space_ndim = syst._wrapped_symmetry.periods.shape

pytest.ini

 [pytest]
 testpaths = kwant
 flakes-ignore =
-    __init__.py UnusedImport
+    __init__.py UnusedImport ImportStarUsed ImportStarUsage
     kwant/_plotter.py UnusedImport
     graph/tests/test_scotch.py UndefinedName
-    graph/tests/test_dissection.py UndefinedName

setup.py

@@ -517,7 +517,7 @@ def maybe_add_numpy_include(exts):
 
 
 def main():
-    check_python_version((3, 5))
+    check_python_version((3, 6))
     check_versions()
 
     exts = collections.OrderedDict([
@@ -581,12 +581,12 @@ def main():
                     'build_ext': build_ext,
                     'test': test},
           ext_modules=exts,
-          install_requires=['numpy >= 1.11.0', 'scipy >= 0.17.0',
+          install_requires=['numpy >= 1.13.3', 'scipy >= 0.19.1',
                             'tinyarray >= 1.2'],
           extras_require={
               # The oldest versions between: Debian stable, Ubuntu LTS
-              'plotting': 'matplotlib >= 1.5.1',
-              'continuum': 'sympy >= 0.7.6',
+              'plotting': 'matplotlib >= 2.1.1',
+              'continuum': 'sympy >= 1.1.1',
               # qsymm is only packaged on PyPI
               'qsymm': 'qsymm >= 1.2.6',
           },