Add accessor-agnostic update kernel generation functions

and use them for generating stream-pull kernels

lbmpy/updatekernels.py

 import numpy as np
 import sympy as sp
 
-from lbmpy.fieldaccess import StreamPullTwoFieldsAccessor
+from lbmpy.fieldaccess import StreamPullTwoFieldsAccessor, StreamPushTwoFieldsAccessor
 from lbmpy.methods.abstractlbmethod import LbmCollisionRule
 from pystencils import Assignment, AssignmentCollection, Field
 from pystencils.field import create_numpy_array_with_layout, layout_string_to_tuple
@@ -54,9 +54,9 @@ def create_lbm_kernel(collision_rule, input_field, output_field, accessor):
     return result
 
 
-def create_stream_pull_only_kernel(stencil, numpy_arr=None, src_field_name="src", dst_field_name="dst",
-                                   generic_layout='numpy', generic_field_type=np.float64):
-    """Creates a stream-pull kernel, without collision.
+def create_stream_only_kernel(stencil, numpy_arr=None, src_field_name="src", dst_field_name="dst",
+                                   generic_layout='numpy', generic_field_type=np.float64, accessor=None):
+    """Creates a stream kernel, without collision.
 
     For parameters see function ``create_stream_pull_collide_kernel``
     """
@@ -71,16 +71,19 @@ def create_stream_pull_only_kernel(stencil, numpy_arr=None, src_field_name="src"
         src = Field.create_from_numpy_array(src_field_name, numpy_arr, index_dimensions=1)
         dst = Field.create_from_numpy_array(dst_field_name, numpy_arr, index_dimensions=1)
 
-    accessor = StreamPullTwoFieldsAccessor()
     eqs = [Assignment(a, b) for a, b in zip(accessor.write(dst, stencil), accessor.read(src, stencil))]
     return AssignmentCollection(eqs, [])
 
+def create_stream_pull_only_kernel(stencil, numpy_arr=None, src_field_name="src", dst_field_name="dst",
+                                   generic_layout='numpy', generic_field_type=np.float64):
+    return create_stream_only_kernel(stencil, numpy_arr=numpy_arr, src_field_name=src_field_name, dst_field_name=dst_field_name,
+                                   generic_layout=generic_layout, generic_field_type=generic_field_type, accessor=StreamPullTwoFieldsAccessor())
+
 
-def create_stream_pull_with_output_kernel(lb_method, src_field, dst_field, output):
+def create_stream_with_output_kernel(lb_method, src_field, dst_field, output, accessor):
     stencil = lb_method.stencil
     cqc = lb_method.conserved_quantity_computation
     streamed = sp.symbols("streamed_:%d" % (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)
     write_eqs = [Assignment(a, b) for a, b in zip(accessor.write(dst_field, stencil), streamed)]
@@ -90,6 +93,9 @@ def create_stream_pull_with_output_kernel(lb_method, src_field, dst_field, outpu
     return LbmCollisionRule(lb_method, main_eqs, subexpressions,
                             simplification_hints=output_eq_collection.simplification_hints)
 
+def create_stream_pull_with_output_kernel(lb_method, src_field, dst_field, output):
+    return create_stream_with_output_kernel(lb_method, src_field, dst_field, output, accessor=StreamPullTwoFieldsAccessor())
+
 # ---------------------------------- Pdf array creation for various layouts --------------------------------------------