Show GPU time used.

diff --git a/flow.cpp b/flow.cpp
index 205b24f098e4035f9f725a2f16e0c8b493fe6289..7f714c274c0837c17b74de5ead62172b3c45349c 100644 (file)
--- a/flow.cpp
+++ b/flow.cpp
@@ -455,6 +455,10 @@ int main(void)
        MotionSearch motion_search;
        Densify densify;
 
+       GLuint query;
+       glGenQueries(1, &query);
+       glBeginQuery(GL_TIME_ELAPSED, query);
+
        for (int level = coarsest_level; level >= int(finest_level); --level) {
                int level_width = WIDTH >> level;
                int level_height = HEIGHT >> level;
@@ -507,6 +511,15 @@ int main(void)
 
                prev_level_flow_tex = dense_flow_tex;
        }
+       glEndQuery(GL_TIME_ELAPSED);
+
+       GLint available;
+       do {
+               glGetQueryObjectiv(query, GL_QUERY_RESULT_AVAILABLE, &available);
+       } while (!available);
+       GLuint64 time_elapsed;
+       glGetQueryObjectui64v(query, GL_QUERY_RESULT, &time_elapsed);
+       fprintf(stderr, "GPU time used = %.1f ms\n", time_elapsed / 1e6);
 
        int level_width = WIDTH >> finest_level;
        int level_height = HEIGHT >> finest_level;