"Hdf-forum on behalf of Aaron Friesz" wrote: Hi Mark, Thanks for your response.
In terms of efficiency, since I will likely do output of this type several hundred or thousand times in a single run, I will end up defining a new MPI communicator with just the required processes. Well, if you do that, *and* if you want to use only those processors to make HDF5 calls to create datasets *and* write data, then you will also need to *open* the HDF5 file with that new communicator. I was just hoping that HDF5 could do it for me Nope. Alas, HDF5 isn't going to help in creating MPI communicators for only those processors with data. since writing code to determine which processes should participate, dataset sizes, etc is going to be tedious. int haveData = 0; MPI_Comm newComm; /* set haveData to 1 if this proc has data */ MPI_Comm_split(MPI_COMM_WORLD, haveData, haveData, &newComm); Now, newComm is a communicator which involves *only* the processors with data ordered in rank according to their old ranks. -- Miller, Mark C. "Those who would [, even temporarily,] sacrafice essential liberties in the name of security deserve neither." BF*
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