WIP : add cubic_lattice generator

dwave/embedding/cubic_lattice.py

@@ -0,0 +1,144 @@
+# Copyright 2020 D-Wave Systems Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+#
+# =============================================================================
+from networkx import grid_graph
+from dwave_networkx import pegasus_graph, chimera_graph
+from dwave.embedding.exceptions import *
+from dwave.embedding.diagnostic import diagnose_embedding, verify_embedding
+from dimod.generators import doped
+
+def _pegasus_cubic(x, y, z):
+    return [(z // 4, y, x, 0, z % 4), (z // 4, y, x, 1, z % 4)]
+
+
+def _chimera_cubic_z12(x, y, z):
+    return [(y * 3 + i, x * 3 + z // 4, 0, z % 4) for i in range(3)] + [(y * 3 + z // 4, x * 3 + i, 1, z % 4) for i in
+                                                                        range(3)]
+
+
+def _chimera_cubic_z8_v1(x, y, z):
+    k, d = divmod(z, 2)
+    return [(2 * y, 2 * x + d, 0, k), (2 * y + 1, 2 * x + d, 0, k), (2 * y + d, 2 * x, 1, k),
+            (2 * y + d, 2 * x + 1, 1, k)]
+
+
+def _chimera_cubic_z8_v2(x, y, z):
+    d, k = divmod(z, 4)
+    return [(2 * y, 2 * x + d, 0, k), (2 * y + 1, 2 * x + d, 0, k), (2 * y + d, 2 * x, 1, k),
+            (2 * y + d, 2 * x + 1, 1, k)]
+
+
+def _cubic_lattice_pegasus(size, grid=(12, 5, 5)):
+    """ given the target size of a pegasus graph and the grid, will return the
+        cubic lattice embedding of the given grid on a complete pegasus of size. """
+
+    pegasus = pegasus_graph(size, nice_coordinates = True)
+    g = grid_graph(list(grid))
+
+    emb = {v: _pegasus_cubic(*v) for v in g}
+    relabeled_emb = {k: [pegasus.nodes[vi]['linear_index'] for vi in v] for k, v in emb.items()}
+    return relabeled_emb
+
+
+def _cubic_lattice_chimera(size, version=1, grid=(8, 8, 8)):
+    """ given the target size of a chimera graph, can only be 16, embedding version and the grid, will return the
+        cubic lattice embedding of the given grid on a complete C16. """
+
+    if size < 16:
+        raise ValueError("cannot generate cubic lattice for chimera size < 16")
+    chimera = chimera_graph(size, coordinates=True)
+
+    g = grid_graph(list(grid))
+
+    if grid == (8, 8, 8):
+        if version == 1:
+            emb = {v: _chimera_cubic_z8_v1(*v) for v in g}
+        elif version == 2:
+            emb = {v: _chimera_cubic_z8_v2(*v) for v in g}
+    else:
+        emb = {v: _chimera_cubic_z12(*v) for v in g}
+
+    relabeled_emb = {k: [chimera.nodes[vi]['linear_index'] for vi in v] for k, v in emb.items()}
+    return relabeled_emb
+
+
+def _clean_embedding(embedding, source, target):
+    """ given an embedding for a complete chimera/pegasus, and a target graph of a chimera/pegasus with missing
+        nodes/edges the function will clean the source graph and the embedding """
+    to_remove = set(())
+
+    for x in diagnose_embedding(embedding, source, target):
+
+        if issubclass(x[0], InvalidNodeError) or isinstance(x[0], DisconnectedChainError):
+            to_remove.add(x[1])
+        elif issubclass(x[0], MissingEdgeError):
+            to_remove.add(x[1])
+            to_remove.add(x[2])
+        elif issubclass(x[0], DisconnectedChainError):
+            to_remove.add(x[1])
+        else:
+            raise TypeError("Do not know how to handle {}".format(x[0]))
+
+    source.remove_nodes_from(to_remove)
+    [embedding.pop(key) for key in to_remove]
+
+    if verify_embedding(embedding, source, target):
+        return embedding, source
+    else:
+        raise EmbeddingError("Couldn't find a cubic lattice embedding")
+
+
+def cubic_lattice_embedding(source, target, version=1):
+    """
+
+    Args:
+        source (:obj:`~networkx.Graph`): A grid graph of dimensions (8,8,8) or (12,5,5). It will be modified in
+            place based on the nodes of the target graph.
+        target (:obj:`~networkx.Graph`): A pegasus or a chimera graph.
+        version (int): only applicable for chimera (8,8,8) grid. can be 1 or 2. toggles between different modes
+            of cubic lattice generation.
+
+    Returns (dict): cubic lattice embedding
+
+    """
+    try:
+        topology = target.graph['family']
+        size = target.graph['rows']
+        grid = tuple([x + 1 for x in list(source.nodes)[-1]])
+
+    except:
+        raise TypeError('the graph family should be either chimera or pegasus, received nothing')
+
+    if topology == 'pegasus':
+        embedding = _cubic_lattice_pegasus(size, grid=grid)
+
+    elif topology == 'chimera':
+        embedding = _cubic_lattice_chimera(size, version=version, grid=grid)
+
+    else:
+        raise TypeError("Don't know how to generate cubic lattice for topology {}".format(topology))
+
+    embedding, source = _clean_embedding(embedding, source, target)
+    return embedding, source
+
+
+def cubic_lattice(target, grid, version=1, doping=0, seed=None):
+    source = grid_graph(list(grid))
+    embedding, source = cubic_lattice_embedding(source, target, version)
+    bqm = doped(doping, source, seed=seed)
+
+    return bqm, embedding
+
+

tests/test_cubic_lattice.py

@@ -0,0 +1,49 @@
+# Copyright 2016 D-Wave Systems Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+#
+# ================================================================================================
+
+import unittest
+from dwave.system import DWaveSampler
+from networkx import grid_graph
+from dwave_networkx import chimera_graph, draw_chimera_embedding
+from dwave.embedding.exceptions import *
+from dwave.embedding.diagnostic import diagnose_embedding, verify_embedding
+
+
+class Test_cubic_lattice(unittest.TestCase):
+    def test_chimera_888_v1(self):
+
+        size = 16
+        sampler = DWaveSampler()
+        target = chimera_graph(size, edge_list=sampler.edgelist, node_list=sampler.nodelist)
+
+        grid = (8, 8, 8)
+        source = grid_graph(list(grid))
+        bqm, embedding = cubic_lattice(target, (8, 8, 8), doping=1)
+
+        draw_chimera_embedding(target, emb=embedding)
+        plt.show()
+        print(bqm)
+
+    def test_chimera_888_v2(self):
+
+    def test_chimera_1255(self):
+
+    def test_pegasus_p6(self):
+
+    def test_pegasus_p16(self):
+
+
+