Better wording in warning message which is issued if the reduction operation

failed while dumping the value of a grid scalar during a multiprocessor run.
This closes BetaThorns/1564.


git-svn-id: http://svn.cactuscode.org/arrangements/CactusPUGHIO/IOFlexIO/trunk@281 ebee0441-1374-4afa-a3b5-247f3ba15b9a

1 files changed, 27 insertions, 16 deletions

diff --git a/src/DumpVar.c b/src/DumpVar.c
index 117bf5f..d57b6ac 100644
--- a/src/DumpVar.c
+++ b/src/DumpVar.c
@@ -222,26 +222,37 @@ static int WriteGS (const cGH *GH, const ioRequest *request, IOFile file)
           CCTK_VarDataPtrI (GH, request->timelevel, request->vindex),
           hdatatypesize);
 
-  i = CCTK_ReductionHandle ("sum");
-  if (CCTK_ReduceArray (GH, -1, i, nprocs, request->hdatatype,
-                        buffer, 1, 1, request->hdatatype, nprocs, buffer))
+  if (nprocs > 1)
   {
-    CCTK_VWarn (1, __LINE__, __FILE__, CCTK_THORNSTRING,
-                "WriteGS: Failed to reduce grid scalar '%s'", fullname);
-  }
-  else
-  {
-    retval = 0;
-    for (i = 1; i < nprocs; i++)
-    {
-      retval |= memcmp (buffer, buffer + i*hdatatypesize, hdatatypesize);
+    i = CCTK_ReductionHandle ("sum");
+    if (i >= 0)
+    {  
+      i = CCTK_ReduceArray (GH, -1, i, nprocs, request->hdatatype,
+                            buffer, 1, 1, request->hdatatype, nprocs, buffer);
     }
-    if (retval)
+    if (i < 0)
     {
       CCTK_VWarn (1, __LINE__, __FILE__, CCTK_THORNSTRING,
-                  "WriteGS: value of grid scalar variable '%s' (timelevel %d) "
-                  "differs between processors, only value from processor 0 "
-                  "will be written", fullname, request->timelevel);
+                  "WriteGS: Cannot check whether values on different "
+                  "processors are the same for grid scalar '%s'", fullname);
+
+      /* copy this processor's value to the start of buffer */
+      memcpy (buffer, buffer + myproc*hdatatypesize, hdatatypesize);
+    }
+    else
+    {
+      retval = 0;
+      for (i = 1; i < nprocs; i++)
+      {
+        retval |= memcmp (buffer, buffer + i*hdatatypesize, hdatatypesize);
+      }
+      if (retval)
+      {
+        CCTK_VWarn (1, __LINE__, __FILE__, CCTK_THORNSTRING,
+                    "WriteGS: value of grid scalar variable '%s' (timelevel %d)"
+                    " differs between processors, only value from processor 0 "
+                    "will be written", fullname, request->timelevel);
+      }
     }
   }