Fixed incomplete communication stencil for D3Q15

(and any other stencil omitting certain sub-diagonal directions)

lbmpy/advanced_streaming/communication.py

+import itertools
 from pystencils import Field, Assignment
 from pystencils.slicing import shift_slice, get_slice_before_ghost_layer, normalize_slice
 from lbmpy.advanced_streaming.utility import is_inplace, get_accessor, numeric_index, \
@@ -59,14 +60,17 @@ def get_communication_slices(
     Return the source and destination slices for periodicity handling or communication between blocks.
 
     :param stencil: The stencil used by the LB method.
-    :param comm_stencil: The stencil defining the communication directions. If None, it will be set to stencil.
+    :param comm_stencil: The stencil defining the communication directions. If None, it will be set to the 
+                         full stencil (D2Q9 in 2D, D3Q27 in 3D, etc.).
     :param streaming_pattern: The streaming pattern.
     :param prev_timestep: Timestep after which communication is run.
     :param ghost_layers: Number of ghost layers in each direction.
 
     """
+
+    dim = len(stencil[0])
     if comm_stencil is None:
-        comm_stencil = stencil
+        comm_stencil = itertools.product(*([-1, 0, 1] for _ in range(dim)))
 
     pdfs = Field.create_generic('pdfs', spatial_dimensions=len(stencil[0]), index_shape=(len(stencil),))
     write_accesses = get_accessor(streaming_pattern, prev_timestep).write(pdfs, stencil)
@@ -168,8 +172,9 @@ class LBMPeriodicityHandling:
             stencil = get_stencil(stencil)
 
         self.stencil = stencil
+        self.dim = len(stencil[0])
         self.dh = data_handling
-        
+
         target = data_handling.default_target
         assert target in ['cpu', 'gpu', 'opencl']
 
@@ -184,13 +189,16 @@ class LBMPeriodicityHandling:
         self.pycuda_direct_copy = target == 'gpu' and pycuda_direct_copy
 
         def is_copy_direction(direction):
+            s = 0
             for d, p in zip(direction, periodicity):
+                s += abs(d)
                 if d != 0 and not p:
                     return False
 
-            return True
+            return s != 0
 
-        copy_directions = tuple(filter(is_copy_direction, stencil[1:]))
+        full_stencil = itertools.product(*([-1, 0, 1] for _ in range(self.dim)))
+        copy_directions = tuple(filter(is_copy_direction, full_stencil))
         self.comm_slices = []
         timesteps = get_timesteps(streaming_pattern)
         for timestep in timesteps:
@@ -224,7 +232,7 @@ class LBMPeriodicityHandling:
         for src, dst in self.comm_slices[timestep.idx]:
             kernels.append(
                 periodic_pdf_copy_kernel(
-                    pdf_field, src, dst, target=self.target, 
+                    pdf_field, src, dst, target=self.target,
                     opencl_queue=self.opencl_queue, opencl_ctx=self.opencl_ctx))
         return kernels
 

lbmpy_tests/advanced_streaming/test_communication.py

+import pystencils as ps
+
 import numpy as np
+
 from lbmpy.stencils import get_stencil
 from pystencils.slicing import get_slice_before_ghost_layer, get_ghost_region_slice
-from lbmpy.advanced_streaming.communication import get_communication_slices, _fix_length_one_slices
+from lbmpy.creationfunctions import create_lb_update_rule
+from lbmpy.advanced_streaming.communication import get_communication_slices, _fix_length_one_slices, \
+    LBMPeriodicityHandling
 from lbmpy.advanced_streaming.utility import streaming_patterns, Timestep
 
 import pytest
 
-@pytest.mark.parametrize('stencil', ['D2Q9', 'D3Q19', 'D3Q27'])
+
+@pytest.mark.parametrize('stencil', ['D2Q9', 'D3Q15', 'D3Q19', 'D3Q27'])
 @pytest.mark.parametrize('streaming_pattern', streaming_patterns)
 @pytest.mark.parametrize('timestep', [Timestep.EVEN, Timestep.ODD])
 def test_slices_not_empty(stencil, streaming_pattern, timestep):
     stencil = get_stencil(stencil)
     dim = len(stencil[0])
     q = len(stencil)
-    arr = np.zeros( (4,) * dim + (q,) )
-    slices = get_communication_slices(stencil, streaming_pattern=streaming_pattern, prev_timestep=timestep, ghost_layers=1)
+    arr = np.zeros((4,) * dim + (q,))
+    slices = get_communication_slices(stencil, streaming_pattern=streaming_pattern, prev_timestep=timestep,
+                                      ghost_layers=1)
     for _, slices_list in slices.items():
         for src, dst in slices_list:
             assert all(s != 0 for s in arr[src].shape)
             assert all(s != 0 for s in arr[dst].shape)
 
 
-@pytest.mark.parametrize('stencil', ['D2Q9', 'D3Q19', 'D3Q27'])
+@pytest.mark.parametrize('stencil', ['D2Q9', 'D3Q15', 'D3Q19', 'D3Q27'])
 @pytest.mark.parametrize('streaming_pattern', streaming_patterns)
 @pytest.mark.parametrize('timestep', [Timestep.EVEN, Timestep.ODD])
 def test_src_dst_same_shape(stencil, streaming_pattern, timestep):
     stencil = get_stencil(stencil)
     dim = len(stencil[0])
     q = len(stencil)
-    arr = np.zeros( (4,) * dim + (q,) )
-    slices = get_communication_slices(stencil, streaming_pattern=streaming_pattern, prev_timestep=timestep, ghost_layers=1)
+    arr = np.zeros((4,) * dim + (q,))
+    slices = get_communication_slices(stencil, streaming_pattern=streaming_pattern, prev_timestep=timestep,
+                                      ghost_layers=1)
     for _, slices_list in slices.items():
         for src, dst in slices_list:
             src_shape = arr[src].shape
@@ -37,7 +45,7 @@ def test_src_dst_same_shape(stencil, streaming_pattern, timestep):
             assert src_shape == dst_shape
 
 
-@pytest.mark.parametrize('stencil', ['D2Q9', 'D3Q19', 'D3Q27'])
+@pytest.mark.parametrize('stencil', ['D2Q9', 'D3Q15', 'D3Q19', 'D3Q27'])
 def test_pull_communication_slices(stencil):
     stencil = get_stencil(stencil)
 
@@ -52,9 +60,71 @@ def test_pull_communication_slices(stencil):
                 src = s[0][:-1]
                 dst = s[1][:-1]
                 break
-        
+
         inner_slice = _fix_length_one_slices(get_slice_before_ghost_layer(d, ghost_layers=1))
         inv_dir = (-e for e in d)
         gl_slice = _fix_length_one_slices(get_ghost_region_slice(inv_dir, ghost_layers=1))
         assert src == inner_slice
-        assert dst == gl_slice
\ No newline at end of file
+        assert dst == gl_slice
+
+
+@pytest.mark.parametrize('stencil_name', ['D2Q9', 'D3Q15', 'D3Q19', 'D3Q27'])
+def test_optimised_and_full_communication_equivalence(stencil_name):
+    target = 'cpu'
+    stencil = get_stencil(stencil_name)
+    dim = len(stencil[0])
+    domain_size = (4, ) * dim
+
+    dh = ps.create_data_handling(domain_size, periodicity=(True, ) * dim,
+                                 parallel=False, default_target=target)
+
+    pdf = dh.add_array("pdf", values_per_cell=len(stencil), dtype=np.int64)
+    dh.fill("pdf", 0, ghost_layers=True)
+    pdf_tmp = dh.add_array("pdf_tmp", values_per_cell=len(stencil), dtype=np.int64)
+    dh.fill("pdf_tmp", 0, ghost_layers=True)
+
+    gl = dh.ghost_layers_of_field("pdf")
+
+    num = 0
+    for idx, x in np.ndenumerate(dh.cpu_arrays['pdf']):
+        dh.cpu_arrays['pdf'][idx] = num
+        dh.cpu_arrays['pdf_tmp'][idx] = num
+        num += 1
+
+    ac = create_lb_update_rule(stencil=stencil,
+                               optimization={"symbolic_field": pdf,
+                                             "symbolic_temporary_field": pdf_tmp},
+                               kernel_type='stream_pull_only')
+    ast = ps.create_kernel(ac, target=dh.default_target, cpu_openmp=True)
+    stream = ast.compile()
+
+    full_communication = dh.synchronization_function(pdf.name, target=dh.default_target, optimization={"openmp": True})
+    full_communication()
+
+    dh.run_kernel(stream)
+    dh.swap("pdf", "pdf_tmp")
+    pdf_full_communication = np.copy(dh.cpu_arrays['pdf'])
+
+    num = 0
+    for idx, x in np.ndenumerate(dh.cpu_arrays['pdf']):
+        dh.cpu_arrays['pdf'][idx] = num
+        dh.cpu_arrays['pdf_tmp'][idx] = num
+        num += 1
+
+    optimised_communication = LBMPeriodicityHandling(stencil=stencil, data_handling=dh, pdf_field_name=pdf.name,
+                                                     streaming_pattern='pull')
+    optimised_communication()
+    dh.run_kernel(stream)
+    dh.swap("pdf", "pdf_tmp")
+
+    if dim == 3:
+        for i in range(gl, domain_size[0]):
+            for j in range(gl, domain_size[1]):
+                for k in range(gl, domain_size[2]):
+                    for f in range(len(stencil)):
+                        assert dh.cpu_arrays['pdf'][i, j, k, f] == pdf_full_communication[i, j, k, f], print(f)
+    else:
+        for i in range(gl, domain_size[0]):
+            for j in range(gl, domain_size[1]):
+                for f in range(len(stencil)):
+                    assert dh.cpu_arrays['pdf'][i, j, f] == pdf_full_communication[i, j, f]