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Do not rely on managed memory in EM PIC tutorial #164

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Merged
atmyers merged 1 commit into from
Nov 4, 2025
Merged

Do not rely on managed memory in EM PIC tutorial #164

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15 changes: 12 additions & 3 deletions ExampleCodes/Particles/ElectromagneticPIC/Source/EMParticleContainerInit.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,10 +70,10 @@ InitParticles(const IntVect& a_num_particles_per_cell,
const auto lo = amrex::lbound(tile_box);
const auto hi = amrex::ubound(tile_box);

Gpu::ManagedVector<unsigned int> counts(tile_box.numPts(), 0);
Gpu::DeviceVector<unsigned int> counts(tile_box.numPts(), 0);
unsigned int* pcount = counts.dataPtr();

Gpu::ManagedVector<unsigned int> offsets(tile_box.numPts());
Gpu::DeviceVector<unsigned int> offsets(tile_box.numPts());
unsigned int* poffset = offsets.dataPtr();

amrex::ParallelFor(tile_box,
Expand Down Expand Up @@ -109,7 +109,16 @@ InitParticles(const IntVect& a_num_particles_per_cell,

Gpu::exclusive_scan(counts.begin(), counts.end(), offsets.begin());

int num_to_add = offsets[tile_box.numPts()-1] + counts[tile_box.numPts()-1];
unsigned int last_offset;
unsigned int last_count;
#ifdef AMREX_USE_GPU
Gpu::dtoh_memcpy(&last_offset,offsets.dataPtr()+tile_box.numPts()-1,sizeof(unsigned int));
Gpu::dtoh_memcpy(&last_count,counts.dataPtr()+tile_box.numPts()-1,sizeof(unsigned int));
#else
std::memcpy(&last_offset,offsets.dataPtr()+tile_box.numPts()-1,sizeof(unsigned int)
std::memcpy(&last_count,counts.dataPtr()+tile_box.numPts()-1,sizeof(unsigned int)
#endif
int num_to_add = last_offset + last_count;

auto& particles = GetParticles(lev);
auto& particle_tile = particles[std::make_pair(mfi.index(), mfi.LocalTileIndex())];
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