From 2bc3449d226d669b5c1be48ca4fd185bab8dc36b Mon Sep 17 00:00:00 2001 From: Hal Finkel Date: Tue, 27 Jun 2017 03:04:25 +0000 Subject: [PATCH] Make test/parallel/omp_nested.c not use so many threads I've found it very difficult to get test/parallel/omp_nested.c to pass consistently across my build environments. The problem is that it creates N^2 threads (it is testing nested parallel regions), and that often exceeds the thread limits on systems with many cores. We do raise the process limits in lit, and that often helps, but if running lit with a smaller number of threads or on a system where we're otherwise resource constrained, this particular test tends to fail (because the runtime cannot create a sufficient number of threads). This seems to work: if the maximum number of threads is more than some small number, then cap the number of threads used for the parallel region. The choice of 4 here is somewhat arbitrary. Differential Revision: https://reviews.llvm.org/D32033 llvm-svn: 306357 --- openmp/runtime/test/parallel/omp_nested.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/openmp/runtime/test/parallel/omp_nested.c b/openmp/runtime/test/parallel/omp_nested.c index f73e072b38dc..8b7808890153 100644 --- a/openmp/runtime/test/parallel/omp_nested.c +++ b/openmp/runtime/test/parallel/omp_nested.c @@ -9,6 +9,11 @@ */ int test_omp_nested() { +#ifdef _OPENMP + if (omp_get_max_threads() > 4) + omp_set_num_threads(4); +#endif + int counter = 0; #ifdef _OPENMP omp_set_nested(1);