Merge branch 'RegressionComm' into 'master'

Regression comm

See merge request !141

lbmpy/advanced_streaming/communication.py

 import itertools
 from pystencils import CreateKernelConfig, Field, Assignment, AssignmentCollection
 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, Timestep, get_timesteps
+from lbmpy.advanced_streaming.utility import is_inplace, get_accessor, numeric_index,\
+    Timestep, get_timesteps, numeric_offsets
 from pystencils.datahandling import SerialDataHandling
 from pystencils.enums import Target
 from itertools import chain
@@ -132,6 +133,13 @@ def get_communication_slices(
             origin_slice = get_slice_before_ghost_layer(comm_dir, ghost_layers=ghost_layers, thickness=1)
             src_slice = _fix_length_one_slices(origin_slice)
 
+            write_offsets = numeric_offsets(write_accesses[d])
+            tangential_dir = tuple(s - c for s, c in zip(streaming_dir, comm_dir))
+
+            # TODO: this is just a hotfix. _trim_slice_in_direction breaks FreeSlip BC with adjacent periodic side
+            if streaming_pattern != "pull":
+                src_slice = shift_slice(_trim_slice_in_direction(src_slice, tangential_dir), write_offsets)
+
             neighbour_transform = _get_neighbour_transform(comm_dir, ghost_layers)
             dst_slice = shift_slice(src_slice, neighbour_transform)
 
@@ -210,3 +218,18 @@ def _fix_length_one_slices(slices):
             return slices
     else:
         return tuple(_fix_length_one_slices(s) for s in slices)
+
+
+def _trim_slice_in_direction(slices, direction):
+    assert len(slices) == len(direction)
+
+    result = []
+    for s, d in zip(slices, direction):
+        if isinstance(s, int):
+            result.append(s)
+            continue
+        start = s.start + 1 if d == -1 else s.start
+        stop = s.stop - 1 if d == 1 else s.stop
+        result.append(slice(start, stop, s.step))
+
+    return tuple(result)