CarpetLib: Use busy waiting instead of usleep to calibrate timers

darcs-hash:20070921152348-dae7b-8a3a55574196b28f86afba561d064c89c386c955.gz

1 files changed, 7 insertions, 4 deletions

diff --git a/Carpet/CarpetLib/src/timestat.cc b/Carpet/CarpetLib/src/timestat.cc
index fad45be58..c6bc82c4d 100644
--- a/Carpet/CarpetLib/src/timestat.cc
+++ b/Carpet/CarpetLib/src/timestat.cc
@@ -85,12 +85,15 @@ namespace CarpetLib {
     double const rdummy3 = rdtsc ();
     double const rstart = rdtsc ();
     double const wstart = MPI_Wtime ();
-    int const ierr = usleep (1000 * 1000);
+    // int const ierr = usleep (1000 * 1000);
+    while (MPI_Wtime() < wstart + 1.0) {
+      // do nothing, just wait
+    }
     double const rend = rdtsc ();
     double const wend = MPI_Wtime ();
-    if (ierr) {
-      CCTK_WARN (1, "Could not determine a reliable rdtsc timer resolution");
-    }
+    // if (ierr) {
+    //   CCTK_WARN (1, "Could not determine a reliable rdtsc timer resolution");
+    // }
     rdtsc_cputick *= (wend - wstart) / (rend - rstart);
   }