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Enable OpenMP in addParticles #4615

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Merged
merged 3 commits into from
Aug 20, 2025
Merged

Enable OpenMP in addParticles #4615

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89f47bd
Enable OpenMP in addParticles
atmyers Aug 18, 2025
2e71ca2
move parallel region to include the level too
atmyers Aug 18, 2025
db41d47
touch all tiles in serial first
atmyers Aug 19, 2025
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19 changes: 18 additions & 1 deletion Src/Particle/AMReX_ParticleContainerI.H
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Original file line number Diff line number Diff line change
Expand Up @@ -1166,6 +1166,7 @@ addParticles (const PCType& other, F const& f, bool local)
{
BL_PROFILE("ParticleContainer::addParticles");

// touch all tiles in serial
for (int lev = 0; lev < other.numLevels(); ++lev)
{
const auto& plevel_other = other.GetParticles(lev);
Expand All @@ -1174,7 +1175,23 @@ addParticles (const PCType& other, F const& f, bool local)
auto index = std::make_pair(mfi.index(), mfi.LocalTileIndex());
if(plevel_other.find(index) == plevel_other.end()) { continue; }

auto& ptile = DefineAndReturnParticleTile(lev, mfi.index(), mfi.LocalTileIndex());
DefineAndReturnParticleTile(lev, mfi.index(), mfi.LocalTileIndex());
}
}

#ifdef AMREX_USE_OMP
#pragma omp parallel if (Gpu::notInLaunchRegion())
#endif
for (int lev = 0; lev < other.numLevels(); ++lev)
{
const auto& plevel_other = other.GetParticles(lev);
for(MFIter mfi = other.MakeMFIter(lev); mfi.isValid(); ++mfi)
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This is not related to OpeMP. But we could use this version MFIter MakeMFIter (int lev, const MFItInfo& info) const to disable gpu device sync here and above. If we disable it here, we need to add Gpu::streamSynchronizeAll() after the loop over levels.

Do you want to do this in a follow-up or this PR?

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I will try this in a follow-on PR.

{
auto index = std::make_pair(mfi.index(), mfi.LocalTileIndex());
if(plevel_other.find(index) == plevel_other.end()) { continue; }

// this has already had define() called above
auto& ptile = ParticlesAt(lev, mfi.index(), mfi.LocalTileIndex());
const auto& ptile_other = plevel_other.at(index);
auto np = ptile_other.numParticles();
if (np == 0) { continue; }
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