Merge pull request #561 from OP2/fix/non-determinism

* fix/non-determinism:
  codegen: Fix non-determinism in assumptions ordering

pyop2/codegen/rep2loopy.py

@@ -432,6 +432,16 @@ def generate(builder, wrapper_name=None):
     if wrapper_name is None:
         wrapper_name = "wrap_%s" % builder.kernel.name
 
+    pwaffd = isl.affs_from_space(assumptions.get_space())
+    assumptions = assumptions & pwaffd["start"].ge_set(pwaffd[0])
+    if builder.single_cell:
+        assumptions = assumptions & pwaffd["start"].lt_set(pwaffd["end"])
+    else:
+        assumptions = assumptions & pwaffd["start"].le_set(pwaffd["end"])
+    if builder.extruded:
+        assumptions = assumptions & pwaffd[parameters.layer_start].le_set(pwaffd[parameters.layer_end])
+    assumptions = reduce(operator.and_, assumptions.get_basic_sets())
+
     wrapper = loopy.make_kernel(domains,
                                 statements,
                                 kernel_data=parameters.kernel_data,
@@ -443,15 +453,6 @@ def generate(builder, wrapper_name=None):
                                 lang_version=(2018, 2),
                                 name=wrapper_name)
 
-    # additional assumptions
-    if builder.single_cell:
-        wrapper = loopy.assume(wrapper, "start < end")
-    else:
-        wrapper = loopy.assume(wrapper, "start <= end")
-    wrapper = loopy.assume(wrapper, "start >= 0")
-    if builder.extruded:
-        wrapper = loopy.assume(wrapper, "{0} <= {1}".format(parameters.layer_start, parameters.layer_end))
-
     # prioritize loops
     for indices in context.index_ordering:
         wrapper = loopy.prioritize_loops(wrapper, indices)