Commit acdf2a6f authored by William Gropp's avatar William Gropp
Browse files

[svn-r3067] Added comment about rank sizes in MPIDI_Message_match

parent 10738f76
......@@ -50,6 +50,19 @@ typedef unsigned long MPID_Seqnum_t;
#include "mpichconf.h"
/* For the typical communication system for which the ch3 channel is
appropriate, 16 bits is sufficient for the rank. By also using 16 bits
for the context, we can reduce the size of the match information, which
is beneficial for slower communication links.
Note that the MPICH2 code (in src/mpi) uses int for rank (and usually for
contextids, though some work is needed there).
Note: We need to check for truncation of rank in MPID_Init - it should
confirm that the size of comm_world is less than 2^15, and in an communicator
create (that may make use of dynamically created processes) that the
size of the communicator is within range.
typedef struct MPIDI_Message_match
int32_t tag;
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