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mpi_reduce error
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Jason HK
Jul 19, 2012, 8:55:09 AM7/19/12
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Dear All,
I am working on a project and need to use MPI_REDUCE to collect (and sum up) the arrays calculated on all the computing nodes. Since the array consumes a lot of memory, I dont want to allocate a buffer to store the results. Is it possible to the array allocated on master node (iRank==0) to act as the buffer?
I tried to achieve this goal by doing follows,
call MPI_COMM_GROUP(MPI_COMM_WORLD, MPI_GROUP_World)
ranks(1)=0
call MPI_GROUP_EXCL(MPI_GROUP_World, 1, ranks, MPI_GROUP_Slaves)
call MPI_COMM_CREATE(MPI_COMM_WORLD, MPI_GROUP_Slaves, MPI_COMM_Slaves)
call MPI_REDUCE(Di, Di, blkSize*blkSize*Ny*2, MPI_DOUBLE_PRECISION, MPI_SUM, 0, MPI_COMM_Slaves, iErr)
However, it keeps on reporting segmentation fault when calling MPI_REDUCE
Can anybody tell me why? Is there any tricks in the implementation details of MPI_REDUCE?
Thanks in advance!
Jason
I am working on a project and need to use MPI_REDUCE to collect (and sum up) the arrays calculated on all the computing nodes. Since the array consumes a lot of memory, I dont want to allocate a buffer to store the results. Is it possible to the array allocated on master node (iRank==0) to act as the buffer?
I tried to achieve this goal by doing follows,
call MPI_COMM_GROUP(MPI_COMM_WORLD, MPI_GROUP_World)
ranks(1)=0
call MPI_GROUP_EXCL(MPI_GROUP_World, 1, ranks, MPI_GROUP_Slaves)
call MPI_COMM_CREATE(MPI_COMM_WORLD, MPI_GROUP_Slaves, MPI_COMM_Slaves)
call MPI_REDUCE(Di, Di, blkSize*blkSize*Ny*2, MPI_DOUBLE_PRECISION, MPI_SUM, 0, MPI_COMM_Slaves, iErr)
However, it keeps on reporting segmentation fault when calling MPI_REDUCE
Can anybody tell me why? Is there any tricks in the implementation details of MPI_REDUCE?
Thanks in advance!
Jason
Georg Bisseling
Jul 20, 2012, 1:27:39 PM7/20/12
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You create a new communicator that is MPI_COMM_WORLD \ {rank 0}.
But it seems that you let rank 0 take part in the call to the reduce
over this new communicator (no "if" there).
That may cause the problem.
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But it seems that you let rank 0 take part in the call to the reduce
over this new communicator (no "if" there).
That may cause the problem.
This signature was intentionally left almost blank.
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