From 56b997eee06516166ffec0814d64b51d0a4ff86e Mon Sep 17 00:00:00 2001
From: Hal Finkel <hfinkel@anl.gov>
Date: Tue, 21 Nov 2017 21:11:12 -0600
Subject: [PATCH] Work around MPI bug where MPI_Get_count does not return zero
for zero count
---
GenericIO.cxx | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/GenericIO.cxx b/GenericIO.cxx
index 0d31bae..eb1fb18 100644
--- a/GenericIO.cxx
+++ b/GenericIO.cxx
@@ -122,8 +122,10 @@ void GenericFileIO_MPI::write(const void *buf, size_t count, off_t offset,
if (MPI_File_write_at(FH, offset, (void *) buf, count, MPI_BYTE, &status) != MPI_SUCCESS)
throw runtime_error("Unable to write " + D + " to file: " + FileName);
- int scount;
- (void) MPI_Get_count(&status, MPI_BYTE, &scount);
+ int scount = 0;
+ // On some systems, MPI_Get_count will not return zero even when count is zero.
+ if (count > 0)
+ (void) MPI_Get_count(&status, MPI_BYTE, &scount);
count -= scount;
buf = ((char *) buf) + scount;
@@ -140,8 +142,10 @@ void GenericFileIO_MPICollective::read(void *buf, size_t count, off_t offset,
if (MPI_File_read_at_all(FH, offset, buf, count, MPI_BYTE, &status) != MPI_SUCCESS)
throw runtime_error("Unable to read " + D + " from file: " + FileName);
- int scount;
- (void) MPI_Get_count(&status, MPI_BYTE, &scount);
+ int scount = 0;
+ // On some systems, MPI_Get_count will not return zero even when count is zero.
+ if (count > 0)
+ (void) MPI_Get_count(&status, MPI_BYTE, &scount);
count -= scount;
buf = ((char *) buf) + scount;
--
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