Fix T41193: 2.71 use 100% of CPU at sculpt

Issue wascaused by the famous OpenMP crap in MSVC2013,
so only way is to use openmp threading if number of BVH
nodes is high enough.

Made it 8 for now, which seems to work rather fine on my
laptop and adult dragon from sintel. But maybe it's to be
adjusted a bit more.

1 files changed, 10 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/pbvh.c b/source/blender/blenkernel/intern/pbvh.c
index e4e6105fe8c..7bdce4e19d5 100644
--- a/source/blender/blenkernel/intern/pbvh.c
+++ b/source/blender/blenkernel/intern/pbvh.c
@@ -50,6 +50,13 @@
 
 #define STACK_FIXED_DEPTH   100
 
+/* Setting zero so we can catch bugs in OpenMP/PBVH. */
+#ifdef DEBUG
+#  define PBVH_OMP_LIMIT 0
+#else
+#  define PBVH_OMP_LIMIT 8
+#endif
+
 typedef struct PBVHStack {
 	PBVHNode *node;
 	int revisiting;
@@ -965,7 +972,7 @@ static void pbvh_update_normals(PBVH *bvh, PBVHNode **nodes,
 	 *   can only update vertices marked with ME_VERT_PBVH_UPDATE.
 	 */
 
-#pragma omp parallel for private(n) schedule(static)
+#pragma omp parallel for private(n) schedule(static) if (totnode > PBVH_OMP_LIMIT)
 	for (n = 0; n < totnode; n++) {
 		PBVHNode *node = nodes[n];
 
@@ -1009,7 +1016,7 @@ static void pbvh_update_normals(PBVH *bvh, PBVHNode **nodes,
 		}
 	}
 
-#pragma omp parallel for private(n) schedule(static)
+#pragma omp parallel for private(n) schedule(static) if (totnode > PBVH_OMP_LIMIT)
 	for (n = 0; n < totnode; n++) {
 		PBVHNode *node = nodes[n];
 
@@ -1046,7 +1053,7 @@ void pbvh_update_BB_redraw(PBVH *bvh, PBVHNode **nodes, int totnode, int flag)
 	int n;
 
 	/* update BB, redraw flag */
-#pragma omp parallel for private(n) schedule(static)
+#pragma omp parallel for private(n) schedule(static) if (totnode > PBVH_OMP_LIMIT)
 	for (n = 0; n < totnode; n++) {
 		PBVHNode *node = nodes[n];