Introduce default assignment simplifications

There are many simplifications in pystencils that are usually not applied. They can be applied now by using a simple argument in the configuration.

Fixes #39 (closed)

pystencils_tests/test_astnodes.py

@@ -5,20 +5,12 @@ import pystencils as ps
 from pystencils import Assignment
 from pystencils.astnodes import Block, LoopOverCoordinate, SkipIteration, SympyAssignment
 
-sympy_numeric_version = [int(x, 10) for x in sp.__version__.split('.') if x.isdigit()]
-if len(sympy_numeric_version) < 3:
-    sympy_numeric_version.append(0)
-sympy_numeric_version.reverse()
-sympy_version = sum(x * (100 ** i) for i, x in enumerate(sympy_numeric_version))
-
 dst = ps.fields('dst(8): double[2D]')
 s = sp.symbols('s_:8')
 x = sp.symbols('x')
 y = sp.symbols('y')
 
 
-@pytest.mark.skipif(sympy_version < 10501,
-                    reason="Old Sympy Versions behave differently which wont be supported in the near future")
 def test_kernel_function():
     assignments = [
         Assignment(dst[0, 0](0), s[0]),
@@ -44,8 +36,6 @@ def test_skip_iteration():
     assert skipped.undefined_symbols == set()
 
 
-@pytest.mark.skipif(sympy_version < 10501,
-                    reason="Old Sympy Versions behave differently which wont be supported in the near future")
 def test_block():
     assignments = [
         Assignment(dst[0, 0](0), s[0]),
@@ -92,15 +82,24 @@ def test_loop_over_coordinate():
     assert loop.step == 2
 
 
-def test_sympy_assignment():
+@pytest.mark.parametrize('default_assignment_simplifications', [False, True])
+def test_sympy_assignment(default_assignment_simplifications):
+    import logging
+    logging.basicConfig(level=logging.DEBUG)
     assignment = SympyAssignment(dst[0, 0](0), sp.log(x + 3) / sp.log(2) + sp.log(x ** 2 + 1))
 
-    ast = ps.create_kernel([assignment])
+    config = ps.CreateKernelConfig(default_assignment_simplifications=default_assignment_simplifications)
+    ast = ps.create_kernel([assignment], config=config)
     code = ps.get_code_str(ast)
 
-    assert 'log1p' in code
-    # constant term is directly evaluated
-    assert 'log2' not in code
+    if default_assignment_simplifications:
+        assert 'log1p' in code
+        # constant term is directly evaluated
+        assert 'log2' not in code
+    else:
+        # no optimisations will be applied so the optimised version of log will not be in the code
+        assert 'log1p' not in code
+        assert 'log2' not in code
 
     assignment.replace(assignment.lhs, dst[0, 0](1))
     assignment.replace(assignment.rhs, sp.log(2))