From 50816cbeb4386c1ff9923e572f31f7fa42ae33b2 Mon Sep 17 00:00:00 2001
From: markus holzer <markus.holzer@fau.de>
Date: Thu, 10 Jun 2021 11:48:19 +0200
Subject: [PATCH] Cleaned update kernels
---
lbmpy/updatekernels.py | 52 ++++++++++++++++++++++++++++++++----------
1 file changed, 40 insertions(+), 12 deletions(-)
diff --git a/lbmpy/updatekernels.py b/lbmpy/updatekernels.py
index f979880b..0673f37e 100644
--- a/lbmpy/updatekernels.py
+++ b/lbmpy/updatekernels.py
@@ -12,14 +12,13 @@ from pystencils.sympyextensions import fast_subs
# -------------------------------------------- LBM Kernel Creation -----------------------------------------------------
-def create_lbm_kernel(collision_rule, input_field, output_field, accessor):
+def create_lbm_kernel(collision_rule, src_field, dst_field=None, accessor=StreamPullTwoFieldsAccessor()):
"""Replaces the pre- and post collision symbols in the collision rule by field accesses.
Args:
collision_rule: instance of LbmCollisionRule, defining the collision step
- input_field: field used for reading pdf values
- output_field: field used for writing pdf values
- if accessor.is_inplace this parameter is ignored
+ src_field: field used for reading pdf values
+ dst_field: field used for writing pdf values if accessor.is_inplace this parameter is ignored
accessor: instance of PdfFieldAccessor, defining where to read and write values
to create e.g. a fused stream-collide kernel
@@ -27,15 +26,18 @@ def create_lbm_kernel(collision_rule, input_field, output_field, accessor):
LbmCollisionRule where pre- and post collision symbols have been replaced
"""
if accessor.is_inplace:
- output_field = input_field
+ dst_field = src_field
+
+ if not accessor.is_inplace and dst_field is None:
+ raise ValueError("For two field accessors a destination field has to be provided")
method = collision_rule.method
pre_collision_symbols = method.pre_collision_pdf_symbols
post_collision_symbols = method.post_collision_pdf_symbols
substitutions = {}
- input_accesses = accessor.read(input_field, method.stencil)
- output_accesses = accessor.write(output_field, method.stencil)
+ input_accesses = accessor.read(src_field, method.stencil)
+ output_accesses = accessor.write(dst_field, method.stencil)
for (idx, offset), input_access, output_access in zip(enumerate(method.stencil), input_accesses, output_accesses):
substitutions[pre_collision_symbols[idx]] = input_access
@@ -55,7 +57,7 @@ def create_lbm_kernel(collision_rule, input_field, output_field, accessor):
return result
-def create_stream_only_kernel(stencil, src_field, dst_field, accessor=StreamPullTwoFieldsAccessor()):
+def create_stream_only_kernel(stencil, src_field, dst_field=None, accessor=StreamPullTwoFieldsAccessor()):
"""Creates a stream kernel, without collision.
Args:
@@ -67,7 +69,13 @@ def create_stream_only_kernel(stencil, src_field, dst_field, accessor=StreamPull
Returns:
AssignmentCollection of the stream only update rule
"""
- temporary_symbols = sp.symbols(f'tmp_:{len(stencil)}')
+ if accessor.is_inplace:
+ dst_field = src_field
+
+ if not accessor.is_inplace and dst_field is None:
+ raise ValueError("For two field accessors a destination field has to be provided")
+
+ temporary_symbols = sp.symbols(f'streamed_:{len(stencil)}')
subexpressions = [Assignment(tmp, acc) for tmp, acc in zip(temporary_symbols, accessor.read(src_field, stencil))]
main_assignments = [Assignment(acc, tmp) for acc, tmp in zip(accessor.write(dst_field, stencil), temporary_symbols)]
return AssignmentCollection(main_assignments, subexpressions=subexpressions)
@@ -103,13 +111,33 @@ def create_stream_pull_only_kernel(stencil, numpy_arr=None, src_field_name="src"
return create_stream_only_kernel(stencil, src, dst, accessor=StreamPullTwoFieldsAccessor())
-def create_stream_pull_with_output_kernel(lb_method, src_field, dst_field, output):
+def create_stream_pull_with_output_kernel(lb_method, src_field, dst_field=None, output=None,
+ accessor=StreamPullTwoFieldsAccessor()):
+ """Creates a stream kernel, without collision but macroscopic quantaties like density or velocity can be calculated.
+
+ Args:
+ lb_method: lattice Boltzmann method see 'creationfunctions.create_lb_method'
+ src_field: Field the pre-streaming values are read from
+ dst_field: field used for writing pdf values if accessor.is_inplace this parameter is ignored
+ output: Dictonary which containes macroscopic quantities as keys which should be calculated and fields as
+ values which should be used to write the data e.g.: {'density': density_field}
+ accessor: Field accessor which is used to create the update rule. See 'fieldaccess.PdfFieldAccessor'
+
+ Returns:
+ AssignmentCollection of the stream only update rule
+ """
+ if accessor.is_inplace:
+ dst_field = src_field
+
+ if not accessor.is_inplace and dst_field is None:
+ raise ValueError("For two field accessors a destination field has to be provided")
+
stencil = lb_method.stencil
cqc = lb_method.conserved_quantity_computation
streamed = sp.symbols(f"streamed_:{len(stencil)}")
- accessor = StreamPullTwoFieldsAccessor()
stream_assignments = [Assignment(a, b) for a, b in zip(streamed, accessor.read(src_field, stencil))]
- output_eq_collection = cqc.output_equations_from_pdfs(streamed, output)
+ output_eq_collection = cqc.output_equations_from_pdfs(streamed, output) if output\
+ else AssignmentCollection(main_assignments=[])
write_eqs = [Assignment(a, b) for a, b in zip(accessor.write(dst_field, stencil), streamed)]
subexpressions = stream_assignments + output_eq_collection.subexpressions
--
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