diff --git a/doc/source/pre/whatsnew/0.2.rst b/doc/source/pre/whatsnew/0.2.rst
index 3a0e8e95a4a30a86168855fbd017be1279193cfe..2022810f63e0c00d3df442d91ff1e772f45ba0d8 100644
--- a/doc/source/pre/whatsnew/0.2.rst
+++ b/doc/source/pre/whatsnew/0.2.rst
@@ -42,7 +42,7 @@ description check `~kwant.plotter.plot` documentation.
The behavior of `~kwant.plotter.plot` with low level systems has changed.
Arguments of plot which are functions are given site numbers in place of
-`~kwant.builder.Site` objects when plotting a low level system. This
+`~kwant.system.Site` objects when plotting a low level system. This
provides an easy way to make the appearance of lines and symbols depend on
computation results.
diff --git a/doc/source/pre/whatsnew/1.0.rst b/doc/source/pre/whatsnew/1.0.rst
index 1eb4cf07efa8cda9b030497893b99b263afbabd7..473e414af1052f24ef271e38a2bd2b92ba34d361 100644
--- a/doc/source/pre/whatsnew/1.0.rst
+++ b/doc/source/pre/whatsnew/1.0.rst
@@ -39,7 +39,7 @@ now it suffices to write ::
syst[lat.neighbors()] = t
This is possible because `~kwant.builder.Builder` now accepts *functions* as
-keys in addition to `~kwant.builder.Site` objects and tuples of them
+keys in addition to `~kwant.system.Site` objects and tuples of them
(hoppings). These functions are expected to yield either sites or hoppings,
when given a builder instance as the sole argument. The use of such keys is to
implement sets of sites or hoppings that depend on what is already present in
diff --git a/doc/source/reference/kwant.builder.rst b/doc/source/reference/kwant.builder.rst
index 327afca9e9f44c797378b918baa0799ef30af45f..f453d40217ca545a38f2ab7744b3febd2f13786a 100644
--- a/doc/source/reference/kwant.builder.rst
+++ b/doc/source/reference/kwant.builder.rst
@@ -9,7 +9,6 @@ Types
:toctree: generated/
Builder
- Site
HoppingKind
SimpleSiteFamily
BuilderLead
@@ -23,7 +22,6 @@ Abstract base classes
.. autosummary::
:toctree: generated/
- SiteFamily
Symmetry
Lead
diff --git a/doc/source/reference/kwant.system.rst b/doc/source/reference/kwant.system.rst
index 3b6f26274da393807c37c6c2826ce5518fe41c7d..6d6dbec6d73187f14143099cbf6ec10bda12559e 100644
--- a/doc/source/reference/kwant.system.rst
+++ b/doc/source/reference/kwant.system.rst
@@ -19,6 +19,16 @@ In practice, very often Kwant systems are finalized
`kwant.builder.FiniteSystem` or `kwant.builder.InfiniteSystem`) and offer some
additional attributes.
+Sites
+-----
+.. autosummary::
+ :toctree: generated/
+
+ Site
+ SiteFamily
+
+Systems
+--------
.. autosummary::
:toctree: generated/
diff --git a/doc/source/tutorial/first_steps.rst b/doc/source/tutorial/first_steps.rst
index 41ed21bb7fdfef0279b95f000db6d9199fa9ed63..b0760b6432e4d22003aa8bdfb9c18e5352999972 100644
--- a/doc/source/tutorial/first_steps.rst
+++ b/doc/source/tutorial/first_steps.rst
@@ -358,13 +358,13 @@ subbands that increases with energy.
**sites** as indices. Sites themselves have a certain type, and
belong to a **site family**. A site family is also used to convert
something that represents a site (like a tuple) into a
- proper `~kwant.builder.Site` object that can be used with
+ proper `~kwant.system.Site` object that can be used with
`~kwant.builder.Builder`.
In the above example, `lat` is the site family. ``lat(i, j)``
then translates the description of a lattice site in terms of two
integer indices (which is the natural way to do here) into
- a proper `~kwant.builder.Site` object.
+ a proper `~kwant.system.Site` object.
The concept of site families and sites allows `~kwant.builder.Builder`
to mix arbitrary lattices and site families
diff --git a/doc/source/tutorial/operators.rst b/doc/source/tutorial/operators.rst
index ed346f178fc3582a2f8909c8bc4cc76de03cad53..1fdd27871a4f3852df6b32ea92f1b9d633bb6897 100644
--- a/doc/source/tutorial/operators.rst
+++ b/doc/source/tutorial/operators.rst
@@ -438,7 +438,7 @@ the `~kwant.operator.Current`, instead of a constant matrix:
# evaluate the operator
m_current = J_m(psi, params=dict(r0=25, delta=10))
-The function must take a `~kwant.builder.Site` as its first parameter,
+The function must take a `~kwant.system.Site` as its first parameter,
and may optionally take other parameters (i.e. it must have the same
signature as a Hamiltonian onsite function), and must return the square
matrix that defines the operator we wish to calculate.
@@ -529,8 +529,8 @@ We see that the probability current is conserved across the scattering region,
but the z-projected spin current is not due to the fact that the Hamiltonian
does not commute with :math:`σ_z` everywhere in the scattering region.
-.. note:: ``where`` can also be provided as a sequence of `~kwant.builder.Site`
- or a sequence of hoppings (i.e. pairs of `~kwant.builder.Site`),
+.. note:: ``where`` can also be provided as a sequence of `~kwant.system.Site`
+ or a sequence of hoppings (i.e. pairs of `~kwant.system.Site`),
rather than a function.
diff --git a/doc/source/tutorial/plotting.rst b/doc/source/tutorial/plotting.rst
index bf6b51ae7e148fc6fdad8c37c5f24ed57421a079..48b6ed4796251b64aa9de10922ce911cd3aade86 100644
--- a/doc/source/tutorial/plotting.rst
+++ b/doc/source/tutorial/plotting.rst
@@ -105,7 +105,7 @@ the start end end site of hopping as arguments:
kwant.plot(syst, site_lw=0.1, site_color=family_color, hop_lw=hopping_lw);
Note that since we are using an unfinalized Builder, a ``site`` is really an
-instance of `~kwant.builder.Site`. With these adjustments we arrive at a plot
+instance of `~kwant.system.Site`. With these adjustments we arrive at a plot
that carries the same information, but is much easier to interpret.
Apart from plotting the *system* itself, `~kwant.plotter.plot` can also be used
@@ -175,7 +175,7 @@ this is interpreted as the radius of the inner circle).
Finally, note that since we are dealing with a finalized system now, a site `i`
is represented by an integer. In order to obtain the original
-`~kwant.builder.Site`, ``syst.sites[i]`` can be used.
+`~kwant.system.Site`, ``syst.sites[i]`` can be used.
The way how data is presented of course influences what features of the data
are best visible in a given plot. With `~kwant.plotter.plot` one can easily go
diff --git a/doc/source/tutorial/spin_potential_shape.rst b/doc/source/tutorial/spin_potential_shape.rst
index b87eaa7f6afced106110ca10823e48a6cb667069..23d90bf8bbf384af9d3644a34867c635c5eaf115 100644
--- a/doc/source/tutorial/spin_potential_shape.rst
+++ b/doc/source/tutorial/spin_potential_shape.rst
@@ -285,7 +285,7 @@ define the potential profile of a quantum well as:
else:
return 0
-This function takes two arguments: the first of type `~kwant.builder.Site`,
+This function takes two arguments: the first of type `~kwant.system.Site`,
from which you can get the real-space coordinates using ``site.pos``, and the
value of the potential as the second. Note that in `potential` we can access
variables `L` and `L_well` that are defined globally.
@@ -375,10 +375,10 @@ oscillatory transmission behavior through resonances in the quantum well.
.. specialnote:: Technical details
- Functions can also be used for hoppings. In this case, they take
- two `~kwant.builder.Site`'s as arguments and then an arbitrary number
+ two `~kwant.system.Site`'s as arguments and then an arbitrary number
of additional arguments.
- - Apart from the real-space position `pos`, `~kwant.builder.Site` has also an
+ - Apart from the real-space position `pos`, `~kwant.system.Site` has also an
attribute `tag` containing the lattice indices of the site.
.. _tutorial-abring:
@@ -449,7 +449,7 @@ that returns ``True`` whenever a point is inside the shape, and
return (r1 ** 2 < rsq < r2 ** 2)
Note that this function takes a real-space position as argument (not a
-`~kwant.builder.Site`).
+`~kwant.system.Site`).
We can now simply add all of the lattice points inside this shape at
once, using the function `~kwant.lattice.Square.shape`
diff --git a/kwant/builder.py b/kwant/builder.py
index 390ca0ba3c54d30d080d67c5002b43a49b74f4bf..e28f63f4e4d0b8c941939712098576d6f7daf0a1 100644
--- a/kwant/builder.py
+++ b/kwant/builder.py
@@ -1,4 +1,4 @@
-# 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
@@ -19,6 +19,7 @@ import tinyarray as ta
import numpy as np
from scipy import sparse
from . import system, graph, KwantDeprecationWarning, UserCodeError
+from .system import Site, SiteFamily
from .linalg import lll
from .operator import Density
from .physics import DiscreteSymmetry, magnetic_gauge
@@ -26,182 +27,13 @@ from ._common import (ensure_isinstance, get_parameters, reraise_warnings,
interleave, deprecate_args, memoize)
-__all__ = ['Builder', 'Site', 'SiteFamily', 'SimpleSiteFamily', 'Symmetry',
- 'HoppingKind', 'Lead', 'BuilderLead', 'SelfEnergyLead', 'ModesLead',
- 'add_peierls_phase']
+__all__ = ['Builder', 'SimpleSiteFamily', 'Symmetry', 'HoppingKind', 'Lead',
+ 'BuilderLead', 'SelfEnergyLead', 'ModesLead', 'add_peierls_phase']
-################ 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)
-
+################ Site families
@total_ordering
-class SiteFamily(metaclass=abc.ABCMeta):
- """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 the method `normalize_tag` which brings a tag
- to the standard format for this site family.
-
- Site families that are intended for use with plotting should also provide a
- method `pos(tag)`, which returns a vector with real-space coordinates of the
- site belonging to this family with a given tag.
-
- 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 __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
-
- @abc.abstractmethod
- def normalize_tag(self, tag):
- """Return a normalized version of the tag.
-
- Raises TypeError or ValueError if the tag is not acceptable.
- """
- pass
-
- 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)
-
-
class SimpleSiteFamily(SiteFamily):
"""A site family used as an example and for testing.
@@ -412,8 +244,8 @@ class HoppingKind(tuple):
----------
delta : Sequence of integers
The sequence is interpreted as a vector with integer elements.
- family_a : `~kwant.builder.SiteFamily`
- family_b : `~kwant.builder.SiteFamily` or ``None`` (default)
+ family_a : `~kwant.system.SiteFamily`
+ family_b : `~kwant.system.SiteFamily` or ``None`` (default)
The default value means: use the same family as `family_a`.
Notes
@@ -570,7 +402,7 @@ class BuilderLead(Lead):
The tight-binding system of a lead. It has to possess appropriate
symmetry, and it may not contain hoppings between further than
neighboring images of the fundamental domain.
- interface : sequence of `Site` instances
+ interface : sequence of `~kwant.system.Site` instances
Sequence of sites in the scattering region to which the lead is
attached.
@@ -578,9 +410,9 @@ class BuilderLead(Lead):
----------
builder : `Builder`
The tight-binding system of a lead.
- interface : list of `Site` instances
+ interface : list of `~kwant.system.Site` instances
A sorted list of interface sites.
- padding : list of `Site` instances
+ padding : list of `~kwant.system.Site` instances
A sorted list of sites that originate from the lead, have the same
onsite Hamiltonian, and are connected by the same hoppings as the lead
sites.
@@ -638,7 +470,7 @@ class SelfEnergyLead(Lead):
selfenergy_func : function
Has the same signature as `selfenergy` (without the ``self``
parameter) and returns the self energy matrix for the interface sites.
- interface : sequence of `Site` instances
+ interface : sequence of `~kwant.system.Site` instances
parameters : sequence of strings
The parameters on which the lead depends.
"""
@@ -669,7 +501,7 @@ class ModesLead(Lead):
and returns the modes of the lead as a tuple of
`~kwant.physics.PropagatingModes` and `~kwant.physics.StabilizedModes`.
interface :
- sequence of `Site` instances
+ sequence of `~kwant.system.Site` instances
parameters : sequence of strings
The parameters on which the lead depends.
"""
@@ -797,10 +629,11 @@ class Builder:
This is one of the central types in Kwant. It is used to construct tight
binding systems in a flexible way.
- The nodes of the graph are `Site` instances. The edges, i.e. the hoppings,
- are pairs (2-tuples) of sites. Each node and each edge has a value
- associated with it. The values associated with nodes are interpreted as
- on-site Hamiltonians, the ones associated with edges as hopping integrals.
+ The nodes of the graph are `~kwant.system.Site` instances. The edges,
+ i.e. the hoppings, are pairs (2-tuples) of sites. Each node and each
+ edge has a value associated with it. The values associated with nodes
+ are interpreted as on-site Hamiltonians, the ones associated with edges
+ as hopping integrals.
To make the graph accessible in a way that is natural within the Python
language it is exposed as a *mapping* (much like a built-in Python
@@ -1452,7 +1285,7 @@ class Builder:
A boolean function of site returning whether the site should be
added to the target builder or not. The shape must be compatible
with the symmetry of the target builder.
- start : `Site` instance or iterable thereof or iterable of numbers
+ start : `~kwant.system.Site` or iterable thereof or iterable of numbers
The site(s) at which the the flood-fill starts. If start is an
iterable of numbers, the starting site will be
``template.closest(start)``.
@@ -1462,7 +1295,7 @@ class Builder:
Returns
-------
- added_sites : list of `Site` objects that were added to the system.
+ added_sites : list of `~kwant.system.Site` that were added to the system.
Raises
------
@@ -1614,7 +1447,7 @@ class Builder:
----------
lead_builder : `Builder` with 1D translational symmetry
Builder of the lead which has to be attached.
- origin : `Site`
+ origin : `~kwant.system.Site`
The site which should belong to a domain where the lead should
begin. It is used to attach a lead inside the system, e.g. to an
inner radius of a ring.
@@ -1624,7 +1457,7 @@ class Builder:
Returns
-------
- added_sites : list of `Site` objects that were added to the system.
+ added_sites : list of `~kwant.system.Site`
Raises
------
@@ -2155,11 +1988,11 @@ class FiniteSystem(_FinalizedBuilderMixin, system.FiniteSystem):
Attributes
----------
sites : sequence
- ``sites[i]`` is the `~kwant.builder.Site` instance that corresponds
+ ``sites[i]`` is the `~kwant.system.Site` instance that corresponds
to the integer-labeled site ``i`` of the low-level system. The sites
are ordered first by their family and then by their tag.
- id_by_site : dict
- The inverse of ``sites``; maps high-level `~kwant.builder.Site`
+ id_by_site : mapping
+ The inverse of ``sites``; maps high-level `~kwant.system.Site`
instances to their integer label.
Satisfies ``id_by_site[sites[i]] == i``.
"""
@@ -2275,10 +2108,10 @@ class InfiniteSystem(_FinalizedBuilderMixin, system.InfiniteSystem):
Attributes
----------
sites : sequence
- ``sites[i]`` is the `~kwant.builder.Site` instance that corresponds
+ ``sites[i]`` is the `~kwant.system.Site` instance that corresponds
to the integer-labeled site ``i`` of the low-level system.
- id_by_site : dict
- The inverse of ``sites``; maps high-level `~kwant.builder.Site`
+ id_by_site : mapping
+ The inverse of ``sites``; maps high-level `~kwant.system.Site`
instances to their integer label.
Satisfies ``id_by_site[sites[i]] == i``.
diff --git a/kwant/continuum/discretizer.py b/kwant/continuum/discretizer.py
index 53f2379cd53f17588dc9e59cb0300a11e90c54c3..ce9e6fe2f65bffeed3da826b02f1618e474a1757 100644
--- a/kwant/continuum/discretizer.py
+++ b/kwant/continuum/discretizer.py
@@ -1,4 +1,4 @@
-# Copyright 2011-2017 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
@@ -20,7 +20,7 @@ from sympy.printing.lambdarepr import LambdaPrinter
from sympy.printing.precedence import precedence
from sympy.core.function import AppliedUndef
-from .. import builder, lattice
+from .. import builder, lattice, system
from .. import KwantDeprecationWarning
from .._common import reraise_warnings
from ._common import (sympify, gcd, position_operators, momentum_operators,
@@ -63,7 +63,7 @@ class _DiscretizedBuilder(builder.Builder):
for key, val in itertools.chain(self.site_value_pairs(),
self.hopping_value_pairs()):
- if isinstance(key, builder.Site):
+ if isinstance(key, system.Site):
result.append("# Onsite element:\n")
else:
a, b = key
diff --git a/kwant/continuum/landau_levels.py b/kwant/continuum/landau_levels.py
index 13e70c4e6b7224d3dab456d5a4497587514ea8af..c653c55ef2634cd13e932f0c3f9c5fd026c10ff9 100644
--- a/kwant/continuum/landau_levels.py
+++ b/kwant/continuum/landau_levels.py
@@ -176,7 +176,7 @@ class LandauLattice(kwant.lattice.Monatomic):
"""
A `~kwant.lattice.Monatomic` lattice with a Landau level index per site.
- Site tags (see `~kwant.builder.SiteFamily`) are pairs of integers, where
+ Site tags (see `~kwant.system.SiteFamily`) are pairs of integers, where
the first integer describes the real space position and the second the
Landau level index.
diff --git a/kwant/kpm.py b/kwant/kpm.py
index 5da09b097e394bc57c07c7de97fb958a3665fc3b..44cf9758f4ddfff3f098be074ca929689c562f11 100644
--- a/kwant/kpm.py
+++ b/kwant/kpm.py
@@ -1,5 +1,5 @@
# -*- coding: utf-8 -*-
-# 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
@@ -928,7 +928,7 @@ def RandomVectors(syst, where=None, rng=None):
----------
syst : `~kwant.system.FiniteSystem` or matrix Hamiltonian
If a system is passed, it should contain no leads.
- where : sequence of `int` or `~kwant.builder.Site`, or callable, optional
+ where : sequence of `int` or `~kwant.system.Site`, or callable, optional
Spatial range of the vectors produced. If ``syst`` is a
`~kwant.system.FiniteSystem`, where behaves as in
`~kwant.operator.Density`. If ``syst`` is a matrix, ``where``
@@ -950,7 +950,7 @@ class LocalVectors:
----------
syst : `~kwant.system.FiniteSystem` or matrix Hamiltonian
If a system is passed, it should contain no leads.
- where : sequence of `int` or `~kwant.builder.Site`, or callable, optional
+ where : sequence of `int` or `~kwant.system.Site`, or callable, optional
Spatial range of the vectors produced. If ``syst`` is a
`~kwant.system.FiniteSystem`, where behaves as in
`~kwant.operator.Density`. If ``syst`` is a matrix, ``where``
diff --git a/kwant/lattice.py b/kwant/lattice.py
index 899ce5474216421b97f35b922a51a62cd85b9602..4099890a480bc9f611148fe4e0e4f519e906e2fd 100644
--- a/kwant/lattice.py
+++ b/kwant/lattice.py
@@ -13,7 +13,7 @@ from math import sqrt
from itertools import product
import numpy as np
import tinyarray as ta
-from . import builder
+from . import builder, system
from .linalg import lll
from ._common import ensure_isinstance
@@ -70,7 +70,7 @@ class Polyatomic:
A Bravais lattice with an arbitrary number of sites in the basis.
Contains `Monatomic` sublattices. Note that an instance of ``Polyatomic`` is
- not itself a `~kwant.builder.SiteFamily`, only its sublattices are.
+ not itself a `~kwant.system.SiteFamily`, only its sublattices are.
Parameters
----------
@@ -171,7 +171,7 @@ class Polyatomic:
>>> syst[lat.neighbors()] = 1
"""
def shape_sites(symmetry=None):
- Site = builder.Site
+ Site = system.Site
if symmetry is None:
symmetry = builder.NoSymmetry()
@@ -306,7 +306,7 @@ class Polyatomic:
"""
# This algorithm is not designed to be fast and can be improved,
# however there is no real need.
- Site = builder.Site
+ Site = system.Site
sls = self.sublattices
shortest_hopping = sls[0].n_closest(
sls[0].pos(([0] * sls[0].lattice_dim)), 2)[-1]
@@ -396,12 +396,12 @@ def short_array_str(array):
return full[1 : -1]
-class Monatomic(builder.SiteFamily, Polyatomic):
+class Monatomic(system.SiteFamily, Polyatomic):
"""
A Bravais lattice with a single site in the basis.
- Instances of this class provide the `~kwant.builder.SiteFamily` interface.
- Site tags (see `~kwant.builder.SiteFamily`) are sequences of integers and
+ Instances of this class provide the `~kwant.system.SiteFamily` interface.
+ Site tags (see `~kwant.system.SiteFamily`) are sequences of integers and
describe the lattice coordinates of a site.
``Monatomic`` instances are used as site families on their own or as
diff --git a/kwant/operator.pyx b/kwant/operator.pyx
index a10624d1ccf3d7d6a2a175e16d6e00e3126c3bad..5133ebb522994d288ef2c5344cb9d016366f6fa9 100644
--- a/kwant/operator.pyx
+++ b/kwant/operator.pyx
@@ -13,7 +13,6 @@ import cython
from operator import itemgetter
import functools as ft
import collections
-import numbers
import numpy as np
import tinyarray as ta
@@ -25,7 +24,7 @@ from .graph.core cimport EdgeIterator
from .graph.core import DisabledFeatureError, NodeDoesNotExistError
from .graph.defs cimport gint
from .graph.defs import gint_dtype
-from .system import InfiniteSystem
+from .system import InfiniteSystem, Site
from ._common import UserCodeError, get_parameters, deprecate_args
@@ -179,8 +178,7 @@ def _normalize_site_where(syst, where):
else:
where = [s for s in range(syst.graph.num_nodes) if where(s)]
else:
- # Cannot check for builder.Site due to circular imports
- if not isinstance(where[0], numbers.Integral):
+ if isinstance(where[0], Site):
try:
where = [syst.id_by_site[s] for s in where]
except AttributeError:
@@ -223,8 +221,7 @@ def _normalize_hopping_where(syst, where):
else:
where = list(filter(lambda h: where(*h), syst.graph))
else:
- # Cannot check for builder.Site due to circular imports
- if not isinstance(where[0][0], numbers.Integral):
+ if isinstance(where[0][0], Site):
try:
where = list((syst.id_by_site[a], syst.id_by_site[b])
for a, b in where)
@@ -735,10 +732,10 @@ cdef class Density(_LocalOperator):
maps from site families to square matrices. If a function is given it
must take the same arguments as the onsite Hamiltonian functions of the
system.
- where : sequence of `int` or `~kwant.builder.Site`, or callable, optional
+ where : sequence of `int` or `~kwant.system.Site`, or callable, optional
Where to evaluate the operator. If ``syst`` is not a finalized Builder,
then this should be a sequence of integers. If a function is provided,
- it should take a single `int` or `~kwant.builder.Site` (if ``syst`` is
+ it should take a single `int` or `~kwant.system.Site` (if ``syst`` is
a finalized builder) and return True or False. If not provided, the
operator will be calculated over all sites in the system.
check_hermiticity: bool
@@ -884,11 +881,11 @@ cdef class Current(_LocalOperator):
matrices (scalars are allowed if the site family has 1 orbital per
site). If a function is given it must take the same arguments as the
onsite Hamiltonian functions of the system.
- where : sequence of pairs of `int` or `~kwant.builder.Site`, or callable, optional
+ where : sequence of pairs of `int` or `~kwant.system.Site`, or callable, optional
Where to evaluate the operator. If ``syst`` is not a finalized Builder,
then this should be a sequence of pairs of integers. If a function is
provided, it should take a pair of integers or a pair of
- `~kwant.builder.Site` (if ``syst`` is a finalized builder) and return
+ `~kwant.system.Site` (if ``syst`` is a finalized builder) and return
True or False. If not provided, the operator will be calculated over
all hoppings in the system.
check_hermiticity : bool
@@ -1016,10 +1013,10 @@ cdef class Source(_LocalOperator):
matrices (scalars are allowed if the site family has 1 orbital per
site). If a function is given it must take the same arguments as the
onsite Hamiltonian functions of the system.
- where : sequence of `int` or `~kwant.builder.Site`, or callable, optional
+ where : sequence of `int` or `~kwant.system.Site`, or callable, optional
Where to evaluate the operator. If ``syst`` is not a finalized Builder,
then this should be a sequence of integers. If a function is provided,
- it should take a single `int` or `~kwant.builder.Site` (if ``syst`` is
+ it should take a single `int` or `~kwant.system.Site` (if ``syst`` is
a finalized builder) and return True or False. If not provided, the
operator will be calculated over all sites in the system.
check_hermiticity : bool
diff --git a/kwant/physics/gauge.py b/kwant/physics/gauge.py
index eb4e696164ac9c7c3f9e5ce1c986df601d4d0bb2..cfb927a6fb1e3397ad4d739160f0e4031b736060 100644
--- a/kwant/physics/gauge.py
+++ b/kwant/physics/gauge.py
@@ -1,4 +1,4 @@
-# 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
@@ -303,7 +303,7 @@ def _loops_in_infinite(syst):
extended_sites : callable : int -> Site
Given a site index in the extended system consisting of
two unit cells, returns the associated high-level
- `kwant.builder.Site`.
+ `kwant.system.Site`.
"""
assert isinstance(syst, system.InfiniteSystem)
_check_infinite_syst(syst)
@@ -375,7 +375,7 @@ def _loops_in_composite(syst):
-1 if the site is part of the reduced scattering region (see notes).
extended_sites : callable : int -> Site
Given a site index in the extended scattering region (see notes),
- returns the associated high-level `kwant.builder.Site`.
+ returns the associated high-level `kwant.system.Site`.
Notes
-----
@@ -401,7 +401,7 @@ def _loops_in_composite(syst):
# Get distance matrix for the extended scattering region,
# a function that maps sites to their lead patches (-1 for sites
# in the reduced scattering region), and a function that maps sites
- # to high-level 'kwant.builder.Site' objects.
+ # to high-level 'kwant.system.Site' objects.
distance_matrix, which_patch, extended_sites =\
_extended_scattering_region(syst)
@@ -439,7 +439,7 @@ def _extended_scattering_region(syst):
-1 if the site is part of the reduced scattering region.
extended_sites : callable : int -> Site
Given a site index in the extended scattering region, returns
- the associated high-level `kwant.builder.Site`.
+ the associated high-level `kwant.system.Site`.
Notes
-----
@@ -1027,7 +1027,7 @@ class magnetic_gauge:
The first callable computes the Peierls phase in the scattering
region and the remaining callables compute the Peierls phases
in each of the leads. Each callable takes a pair of
- `~kwant.builder.Site` (a hopping) and returns a unit complex
+ `~kwant.system.Site` (a hopping) and returns a unit complex
number (Peierls phase) that multiplies that hopping.
"""
return self._peierls(syst_field, *lead_fields, tol=tol, average=False)
diff --git a/kwant/plotter.py b/kwant/plotter.py
index fabe5f61c9234b2323e0c11c860962b3b5b2bd5d..a9e5ec42793fb37eee4e5908624443cafc1db59d 100644
--- a/kwant/plotter.py
+++ b/kwant/plotter.py
@@ -1,5 +1,5 @@
# -*- coding: utf-8 -*-
-# 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
@@ -402,7 +402,7 @@ def sys_leads_sites(sys, num_lead_cells=2):
Returns
-------
sites : list of (site, lead_number, copy_number) tuples
- A site is a `~kwant.builder.Site` instance if the system is not finalized,
+ A site is a `~kwant.system.Site` instance if the system is not finalized,
and an integer otherwise. For system sites `lead_number` is `None` and
`copy_number` is `0`, for leads both are integers.
lead_cells : list of slices
@@ -528,7 +528,7 @@ def sys_leads_hoppings(sys, num_lead_cells=2):
Returns
-------
hoppings : list of (hopping, lead_number, copy_number) tuples
- A site is a `~kwant.builder.Site` instance if the system is not finalized,
+ A site is a `~kwant.system.Site` instance if the system is not finalized,
and an integer otherwise. For system sites `lead_number` is `None` and
`copy_number` is `0`, for leads both are integers.
lead_cells : list of slices
@@ -812,7 +812,7 @@ def plot(sys, num_lead_cells=2, unit='nn',
- The meaning of "site" depends on whether the system to be plotted is a
builder or a low level system. For builders, a site is a
- kwant.builder.Site object. For low level systems, a site is an integer
+ kwant.system.Site object. For low level systems, a site is an integer
-- the site number.
- color and symbol definitions may be tuples, but not lists or arrays.
diff --git a/kwant/system.py b/kwant/system.py
index d270691508189866a0d75809917048303443c883..5498ead7987f4674f89eb2fcaf35523156331718 100644
--- a/kwant/system.py
+++ b/kwant/system.py
@@ -1,4 +1,4 @@
-# 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 +8,196 @@
"""Low-level interface of systems"""
-__all__ = ['System', 'FiniteSystem', 'InfiniteSystem']
+__all__ = [
+ 'Site', 'SiteArray', 'SiteFamily',
+ 'System', 'FiniteSystem', 'InfiniteSystem',
+]
import abc
import warnings
+import operator
from copy import copy
+from collections import namedtuple
+from functools import total_ordering
+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)
+
+
+@total_ordering
+class SiteFamily(metaclass=abc.ABCMeta):
+ """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 the method `normalize_tag` which brings a tag
+ to the standard format for this site family.
+
+ Site families that are intended for use with plotting should also provide a
+ method `pos(tag)`, which returns a vector with real-space coordinates of the
+ site belonging to this family with a given tag.
+
+ 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 __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
+
+ @abc.abstractmethod
+ def normalize_tag(self, tag):
+ """Return a normalized version of the tag.
+
+ Raises TypeError or ValueError if the tag is not acceptable.
+ """
+ pass
+
+ 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):
diff --git a/kwant/tests/test_builder.py b/kwant/tests/test_builder.py
index e0ed4bfe274998b684f89d167386f1911ff9c270..f41652a85c1306fbd25e6b1d5015dd1a550d50b2 100644
--- a/kwant/tests/test_builder.py
+++ b/kwant/tests/test_builder.py
@@ -19,7 +19,7 @@ from pytest import raises, warns
from numpy.testing import assert_almost_equal
import kwant
-from kwant import builder
+from kwant import builder, system
from kwant._common import ensure_rng
@@ -421,12 +421,12 @@ 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 +434,15 @@ 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
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]] ==