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Optimize gather_tracks kernel #1125

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Merged
merged 2 commits into from
Aug 21, 2025
Merged

Optimize gather_tracks kernel #1125

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dccc881
Optimize gather_tracks kernel by reducing the number of blocks
beomki-yeo Aug 20, 2025
7d2a240
Merge branch 'main' into optimize-gather-tracks
stephenswat Aug 21, 2025
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5 changes: 5 additions & 0 deletions device/common/include/traccc/ambiguity_resolution/device/gather_tracks.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,11 @@ struct gather_tracks_payload {
*/
vecmem::data::vector_view<unsigned int> sorted_ids_view;

/**
* @brief View object to the updated track
*/
vecmem::data::vector_view<unsigned int> updated_tracks_view;

/**
* @brief View object to the whether track id is updated
*/
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21 changes: 10 additions & 11 deletions device/cuda/src/ambiguity_resolution/greedy_ambiguity_resolution_algorithm.cu
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Expand Up @@ -420,9 +420,6 @@ greedy_ambiguity_resolution_algorithm::operator()(
unsigned int nBlocks_warp =
(n_accepted + nThreads_warp - 1) / nThreads_warp;

unsigned int nThreads_full = 1024;
unsigned int nBlocks_full = (n_tracks + 1023) / 1024;

unsigned int nThreads_rearrange = 1024;
unsigned int nBlocks_rearrange =
(n_accepted + (nThreads_rearrange / kernels::nThreads_per_track) - 1) /
Expand Down Expand Up @@ -591,14 +588,16 @@ greedy_ambiguity_resolution_algorithm::operator()(
.temp_sorted_ids_view = temp_sorted_ids_buffer,
});

kernels::gather_tracks<<<nBlocks_full, nThreads_full, 0, stream>>>(
device::gather_tracks_payload{
.terminate = terminate_device.get(),
.n_accepted = n_accepted_device.get(),
.n_updated_tracks = n_updated_tracks_device.get(),
.temp_sorted_ids_view = temp_sorted_ids_buffer,
.sorted_ids_view = sorted_ids_buffer,
.is_updated_view = is_updated_buffer});
kernels::
gather_tracks<<<nBlocks_adaptive, nThreads_adaptive, 0, stream>>>(
device::gather_tracks_payload{
.terminate = terminate_device.get(),
.n_accepted = n_accepted_device.get(),
.n_updated_tracks = n_updated_tracks_device.get(),
.temp_sorted_ids_view = temp_sorted_ids_buffer,
.sorted_ids_view = sorted_ids_buffer,
.updated_tracks_view = updated_tracks_buffer,
.is_updated_view = is_updated_buffer});

cudaStreamEndCapture(stream, &graph);
cudaGraphInstantiate(&graphExec, graph, nullptr, nullptr, 0);
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6 changes: 4 additions & 2 deletions device/cuda/src/ambiguity_resolution/kernels/gather_tracks.cu
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Expand Up @@ -23,14 +23,16 @@ __global__ void gather_tracks(device::gather_tracks_payload payload) {
vecmem::device_vector<const unsigned int> temp_sorted_ids(
payload.temp_sorted_ids_view);
vecmem::device_vector<unsigned int> sorted_ids(payload.sorted_ids_view);
vecmem::device_vector<unsigned int> updated_tracks(
payload.updated_tracks_view);
vecmem::device_vector<int> is_updated(payload.is_updated_view);

auto globalIndex = threadIdx.x + blockIdx.x * blockDim.x;
const unsigned int n_accepted = *(payload.n_accepted);

// Reset is_updated vector
if (globalIndex < is_updated.size()) {
is_updated[globalIndex] = 0;
if (globalIndex < *(payload.n_updated_tracks)) {
is_updated[updated_tracks[globalIndex]] = 0;
}

if (globalIndex >= n_accepted) {
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