[mpich-discuss] thread MPI calls

[chong tan]

box X86 box running Linux.  MPICH2 1.1 configured with 

 --disable-f77 --disable-f90 --with-device=ch3:nemesis  --enable-fast

machine : 16 cores, load of mem.  running  with mpiexec -n 4

The master process (MPICH rank 0) has 2 thread, main and recv, the locks are constructed using pthread.   The master's
recv function wait for the recv thread to be done with all recieving, then process the data, and reenable the recv thread,
like this:

             main                                                recv thread
  
             recvFunc() {                                   wait for 'run'  
             wait for read-done                          for n processes
             apply data                                              call MPI_IRecv
             signal run                                        MPI_waitall
             }                                                      signal read-done
         
recvFunc is repeatedly called during the life of my applications.  (In a few tests I have, it is called 100+ billion times)

compared to the same application with no thread and using IRecv or Recv, the threaded version can run 20+% 
slower.  From the process monitoring, it looks like the MPI Irecv calls maybe thread. This performance degration
is inline with 2.0.6 configured using --enable-threads=funneled.  The application ran for many hours, so 20% is
significant.

Questions :
-  is MPICH2 1.1 self-sensing ?  that is, does it know it can decide if it has to do thread-multiple ?
-  IRecv and MPI wait all, is that also threaded ? 
-  anyone experimented this before ?

thanks
tan


________________________________
From: Rajeev Thakur <thakur at mcs.anl.gov>
To: mpich-discuss at mcs.anl.gov
Sent: Friday, June 26, 2009 12:12:18 PM
Subject: Re: [mpich-discuss] does 1.1 support real threading of MPI call ?


Yes, it supports MPI_THREAD_MULTIPLE as defined by the MPI standard.
 
Rajeev


________________________________
From: mpich-discuss-bounces at mcs.anl.gov [mailto:mpich-discuss-bounces at mcs.anl.gov] On Behalf Of chong tan
>Sent: Friday, June 26, 2009 2:04 PM
>To: mpich-discuss at mcs.anl.gov
>Subject: [mpich-discuss] does 1.1 support real threading of MPI call ?
>
>
>Does anyone know if the 1.1 release supports real threaded MPI calls.  That is,
>a process, say 1, may contain n threads, and each calling MPI_Send/Recv to
>other processes, but still think they are all process 1 ?
>
>I am not looking at the funneled solution, that does not help me.
>
>thanks
>tan
>
> 
>
>
>


      
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