Parallel Loops Nested Inside Serial Loops

If a parallel loop is nested inside a serial loop, the runtime information reported by LoopTool and LoopReport may be misleading because each loop is stipulated to use the wall-clock time of each of its loop iterations. If an inner loop is parallelized, it is assigned the wall-clock time of each iteration, although some of those iterations are running in parallel.

However, the outer loop is assigned only the runtime of its child, the parallel loop, which will be the runtime of the longest parallel instantiation of the inner loop. This double timing leads to the anomaly of the outer loop apparently consuming less time than the inner loop.