Always use codegen.rewriting.optimize

Pretty much !34 (merged) but with the changes to create_kernel. Can be closed if not wanted. Leaving it here for archiving purposes.

!34 (merged) has the workflow:

assignments = optimize(assignments, optimizations)
ast = create_kernel(assignments)

pystencils/cpu/kernelcreation.py

@@ -8,6 +8,7 @@ from pystencils.astnodes import Block, KernelFunction, LoopOverCoordinate, Sympy
 from pystencils.cpu.cpujit import make_python_function
 from pystencils.data_types import BasicType, StructType, TypedSymbol, create_type
 from pystencils.field import Field, FieldType
+from pystencils.math_optimizations import optims_pystencils_cpu, optimize_assignments
 from pystencils.transformations import (
     add_types, filtered_tree_iteration, get_base_buffer_index, get_optimal_loop_ordering,
     make_loop_over_domain, move_constants_before_loop, parse_base_pointer_info,
@@ -18,7 +19,7 @@ AssignmentOrAstNodeList = List[Union[Assignment, ast.Node]]
 
 def create_kernel(assignments: AssignmentOrAstNodeList, function_name: str = "kernel", type_info='double',
                   split_groups=(), iteration_slice=None, ghost_layers=None,
-                  skip_independence_check=False) -> KernelFunction:
+                  skip_independence_check=False, sympy_optimizations=optims_pystencils_cpu) -> KernelFunction:
     """Creates an abstract syntax tree for a kernel function, by taking a list of update rules.
 
     Loops are created according to the field accesses in the equations.
@@ -54,6 +55,10 @@ def create_kernel(assignments: AssignmentOrAstNodeList, function_name: str = "ke
         else:
             raise ValueError("Term has to be field access or symbol")
 
+    if sympy_optimizations is None:
+        sympy_optimizations = optims_pystencils_cpu
+    assignments = optimize_assignments(assignments, sympy_optimizations)
+
     fields_read, fields_written, assignments = add_types(assignments, type_info, not skip_independence_check)
     all_fields = fields_read.union(fields_written)
     read_only_fields = set([f.name for f in fields_read - fields_written])
@@ -89,8 +94,12 @@ def create_kernel(assignments: AssignmentOrAstNodeList, function_name: str = "ke
     return ast_node
 
 
-def create_indexed_kernel(assignments: AssignmentOrAstNodeList, index_fields, function_name="kernel",
-                          type_info=None, coordinate_names=('x', 'y', 'z')) -> KernelFunction:
+def create_indexed_kernel(assignments: AssignmentOrAstNodeList,
+                          index_fields,
+                          function_name="kernel",
+                          type_info=None,
+                          coordinate_names=('x', 'y', 'z'),
+                          sympy_optimizations=optims_pystencils_cpu) -> KernelFunction:
     """
     Similar to :func:`create_kernel`, but here not all cells of a field are updated but only cells with
     coordinates which are stored in an index field. This traversal method can e.g. be used for boundary handling.
@@ -107,6 +116,11 @@ def create_indexed_kernel(assignments: AssignmentOrAstNodeList, index_fields, fu
         function_name: see documentation of :func:`create_kernel`
         coordinate_names: name of the coordinate fields in the struct data type
     """
+    if sympy_optimizations is None:
+        sympy_optimizations = optims_pystencils_cpu
+
+    assignments = optimize_assignments(assignments, sympy_optimizations)
+
     fields_read, fields_written, assignments = add_types(assignments, type_info, check_independence_condition=False)
     all_fields = fields_read.union(fields_written)