Simpler OpenMP handling & OpenMP parallel boundaries

- periodic kernels not yet OpenMP parallel

cpu/kernelcreation.py

@@ -126,7 +126,7 @@ def createIndexedKernel(listOfEquations, indexFields, functionName="kernel", typ
     return ast
 
 
-def addOpenMP(astNode, schedule="static", numThreads=None):
+def addOpenMP(astNode, schedule="static", numThreads=True):
     """
     Parallelizes the outer loop with OpenMP
 
@@ -134,13 +134,37 @@ def addOpenMP(astNode, schedule="static", numThreads=None):
     :param schedule: OpenMP scheduling policy e.g. 'static' or 'dynamic'
     :param numThreads: explicitly specify number of threads
     """
+    if not numThreads:
+        return
+
     assert type(astNode) is ast.KernelFunction
     body = astNode.body
-    threadsClause = "" if numThreads is None else " num_threads(%s)" % (numThreads,)
+    threadsClause = "" if numThreads else " num_threads(%s)" % (numThreads,)
     wrapperBlock = ast.PragmaBlock('#pragma omp parallel' + threadsClause, body.takeChildNodes())
     body.append(wrapperBlock)
 
     outerLoops = [l for l in body.atoms(ast.LoopOverCoordinate) if l.isOutermostLoop]
     assert outerLoops, "No outer loop found"
     assert len(outerLoops) <= 1, "More than one outer loop found. Which one should be parallelized?"
-    outerLoops[0].prefixLines.append("#pragma omp for schedule(%s)" % (schedule,))
+    loopToParallelize = outerLoops[0]
+    try:
+        loopRange = int(loopToParallelize.stop - loopToParallelize.start)
+    except TypeError:
+        loopRange = None
+
+    if numThreads is None:
+        import multiprocessing
+        numThreads = multiprocessing.cpu_count()
+
+    if loopRange is not None and loopRange < numThreads:
+        containedLoops = [l for l in loopToParallelize.body.args if isinstance(l, LoopOverCoordinate)]
+        if len(containedLoops) == 1:
+            containedLoop = containedLoops[0]
+            try:
+                containedLoopRange = int(containedLoop.stop - containedLoop.start)
+                if containedLoopRange > loopRange:
+                    loopToParallelize = containedLoop
+            except TypeError:
+                pass
+
+    loopToParallelize.prefixLines.append("#pragma omp for schedule(%s)" % (schedule,))