Merge branch 'fix_cumulant_simplifications' into 'master'

Fix uninserted aliases in cumulant collision rules + new test cases

See merge request !158

lbmpy/simplificationfactory.py

@@ -92,6 +92,7 @@ def _cumulant_space_simplification(split_inner_loop):
     s.add(expand_post_collision_central_moments)
     s.add(insert_aliases)
     s.add(insert_constants)
+    s.add(insert_aliases)
     s.add(add_subexpressions_for_divisions)
     s.add(add_subexpressions_for_constants)
     if split_inner_loop:

lbmpy_tests/test_mrt_simplifications.py

+import pytest
+
+import sympy as sp
+
+from pystencils.sympyextensions import is_constant
+
+from lbmpy import Stencil, LBStencil, Method, create_lb_collision_rule, LBMConfig, LBMOptimisation
+
+# TODO:
+# Fully simplified kernels should NOT contain
+#  - Any aliases
+#  - Any in-line constants (all constants should be in subexpressions!)
+
+@pytest.mark.parametrize('method', [Method.MRT, Method.CENTRAL_MOMENT, Method.CUMULANT])
+def test_mrt_simplifications(method: Method):
+    stencil = Stencil.D3Q19
+    lbm_config = LBMConfig(stencil=stencil, method=method, compressible=True)
+    lbm_opt = LBMOptimisation(simplification='auto')
+
+    cr = create_lb_collision_rule(lbm_config=lbm_config, lbm_optimisation=lbm_opt)
+
+    
+    for subexp in cr.subexpressions:
+        rhs = subexp.rhs
+        #   Check for aliases
+        assert not isinstance(rhs, sp.Symbol)
+
+        #   Check for logarithms
+        assert not rhs.atoms(sp.log)
+
+        #   Check for nonextracted constant summands or factors
+        exprs = rhs.atoms(sp.Add, sp.Mul)
+        for expr in exprs:
+            for arg in expr.args:
+                if isinstance(arg, sp.Number):
+                    assert arg in {sp.Number(1), sp.Number(-1)}
+                    
+        #   Check for divisions
+        if not (isinstance(rhs, sp.Pow) and rhs.args[1] < 0):
+            powers = rhs.atoms(sp.Pow)
+            for p in powers:
+                assert p.args[1] > 0