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Workaround to bypass issue observed at very large scale with Fujitsu MPI #2874

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Jul 8, 2022
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Workaround to bypass issue observed at very large scale with Fujitsu MPI #2874

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bdf56b6
don't use MPI_Datatype in MPI gatherv when compiling with the Fujitsu…
lucafedeli88 Jul 8, 2022
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lucafedeli88 Jul 8, 2022
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17 changes: 17 additions & 0 deletions Src/AmrCore/AMReX_TagBox.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -649,7 +649,24 @@ TagBoxArray::collate (Gpu::PinnedVector<IntVect>& TheGlobalCollateSpace) const
//
const IntVect* psend = (count > 0) ? TheLocalCollateSpace.data() : nullptr;
IntVect* precv = TheGlobalCollateSpace.data();

//Issues have been observed with the following call at very large scale when using
//FujitsuMPI. The issue seems to be related to the use of MPI_Datatype. We can
//bypasses the issue by exchanging simpler integer arrays.
#ifndef __FUJITSU
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We found today: the new -Nclang Fujtsu only defines __CLANG_FUJITSU

ParallelDescriptor::Gatherv(psend, count, precv, countvec, offset, IOProcNumber);
#else
const int* psend_int = psend->begin();
int* precv_int = precv->begin();
Long count_int = count * AMREX_SPACEDIM;
auto countvec_int = std::vector<int>(countvec.size());
auto offset_int = std::vector<int>(offset.size());
const auto mul_funct = [](const auto el){return el*AMREX_SPACEDIM;};
std::transform(countvec.begin(), countvec.end(), countvec_int.begin(), mul_funct);
std::transform(offset.begin(), offset.end(), offset_int.begin(), mul_funct);
ParallelDescriptor::Gatherv(
psend_int, count_int, precv_int, countvec_int, offset_int, IOProcNumber);
#endif

#else
TheGlobalCollateSpace = std::move(TheLocalCollateSpace);
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