Merge branch 'l2p' into 'master'

Help CSE in l2p

See merge request !104

sumpy/expansion/local.py

@@ -133,7 +133,7 @@ class VolumeTaylorLocalExpansionBase(LocalExpansionBase):
         bvec = bvec * rscale**-1
         result = sum(
                 coeff
-                * mi_power(bvec, mi)
+                * mi_power(bvec, mi, evaluate=False)
                 / mi_factorial(mi)
                 for coeff, mi in zip(
                         evaluated_coeffs, self.get_full_coefficient_identifiers()))

sumpy/symbolic.py

@@ -111,6 +111,14 @@ if not have_unevaluated_expr:
         return x
 
 
+if USE_SYMENGINE:
+    def unevaluated_pow(a, b):
+        return sym.Pow(a, b)
+else:
+    def unevaluated_pow(a, b):
+        return sym.Pow(a, b, evaluate=False)
+
+
 # {{{ debugging of sympy CSE via Maxima
 
 class _DerivativeKiller(IdentityMapperBase):

sumpy/tools.py

@@ -55,10 +55,15 @@ def mi_factorial(mi):
     return result
 
 
-def mi_power(vector, mi):
+def mi_power(vector, mi, evaluate=True):
     result = 1
     for mi_i, vec_i in zip(mi, vector):
-        result *= vec_i**mi_i
+        if mi_i == 1:
+            result *= vec_i
+        elif evaluate:
+            result *= vec_i**mi_i
+        else:
+            result *= sym.unevaluated_pow(vec_i, mi_i)
     return result