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ITS: use faster atan2 for trackleting #14557

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ITS: use faster atan2 for trackleting #14557

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826d436
ITS: Tracklet use fastATan2
f3sch Aug 5, 2025
a82d4bd
ITS: Tracker use fastATan2
f3sch Aug 5, 2025
efc1022
ITS: GPU: use fastATan2
f3sch Aug 5, 2025
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9 changes: 4 additions & 5 deletions Detectors/ITSMFT/ITS/tracking/GPU/cuda/TrackingKernels.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -29,14 +29,13 @@
#include "ITStracking/IndexTableUtils.h"
#include "ITStracking/MathUtils.h"
#include "ITStracking/ExternalAllocator.h"
#include "DataFormatsITS/TrackITS.h"
#include "ReconstructionDataFormats/Vertex.h"

#include "ITStrackingGPU/TrackerTraitsGPU.h"
#include "ITStrackingGPU/TrackingKernels.h"
#include "ITStrackingGPU/Utils.h"

// O2 track model
#include "MathUtils/Utils.h"
#include "DataFormatsITS/TrackITS.h"
#include "ReconstructionDataFormats/Vertex.h"
#include "ReconstructionDataFormats/Track.h"
#include "DetectorsBase/Propagator.h"
using namespace o2::track;
Expand Down Expand Up @@ -629,7 +628,7 @@ GPUg() void computeLayerTrackletsMultiROFKernel(
if constexpr (initRun) {
trackletsLUT[layerIndex][currentSortedIndex]++; // we need l0 as well for usual exclusive sums.
} else {
const float phi{o2::gpu::CAMath::ATan2(currentCluster.yCoordinate - nextCluster.yCoordinate, currentCluster.xCoordinate - nextCluster.xCoordinate)};
const float phi{o2::math_utils::fastATan2(currentCluster.yCoordinate - nextCluster.yCoordinate, currentCluster.xCoordinate - nextCluster.xCoordinate)};
const float tanL{(currentCluster.zCoordinate - nextCluster.zCoordinate) / (currentCluster.radius - nextCluster.radius)};
const int nextSortedIndex{ROFClusters[layerIndex + 1][targetROF] + nextClusterIndex};
new (tracklets[layerIndex] + trackletsLUT[layerIndex][currentSortedIndex] + storedTracklets) Tracklet{currentSortedIndex, nextSortedIndex, tanL, phi, pivotROF, targetROF};
Expand Down
6 changes: 3 additions & 3 deletions Detectors/ITSMFT/ITS/tracking/include/ITStracking/Tracklet.h
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Expand Up @@ -18,8 +18,8 @@

#include "ITStracking/Constants.h"
#include "ITStracking/Cluster.h"
#include "MathUtils/Utils.h"
#include "GPUCommonRtypes.h"
#include "GPUCommonMath.h"
#include "GPUCommonDef.h"
#include "GPUCommonLogger.h"

Expand Down Expand Up @@ -67,8 +67,8 @@ GPUhdi() Tracklet::Tracklet(const int firstClusterOrderingIndex, const int secon
secondClusterIndex{secondClusterOrderingIndex},
tanLambda{(firstCluster.zCoordinate - secondCluster.zCoordinate) /
(firstCluster.radius - secondCluster.radius)},
phi{o2::gpu::GPUCommonMath::ATan2(firstCluster.yCoordinate - secondCluster.yCoordinate,
firstCluster.xCoordinate - secondCluster.xCoordinate)},
phi{o2::math_utils::fastATan2(firstCluster.yCoordinate - secondCluster.yCoordinate,
firstCluster.xCoordinate - secondCluster.xCoordinate)},
rof{static_cast<short>(rof0), static_cast<short>(rof1)}
{
// Nothing to do
Expand Down
2 changes: 1 addition & 1 deletion Detectors/ITSMFT/ITS/tracking/src/TrackerTraits.cxx
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Expand Up @@ -173,7 +173,7 @@ void TrackerTraits<nLayers>::computeLayerTracklets(const int iteration, int iROF

if (deltaZ / sigmaZ < mTrkParams[iteration].NSigmaCut &&
((deltaPhi < mTimeFrame->getPhiCut(iLayer) || o2::gpu::GPUCommonMath::Abs(deltaPhi - o2::constants::math::TwoPI) < mTimeFrame->getPhiCut(iLayer)))) {
const float phi{o2::gpu::CAMath::ATan2(currentCluster.yCoordinate - nextCluster.yCoordinate, currentCluster.xCoordinate - nextCluster.xCoordinate)};
const float phi{o2::math_utils::fastATan2(currentCluster.yCoordinate - nextCluster.yCoordinate, currentCluster.xCoordinate - nextCluster.xCoordinate)};
const float tanL = (currentCluster.zCoordinate - nextCluster.zCoordinate) / (currentCluster.radius - nextCluster.radius);
if constexpr (decltype(Tag)::value == PassMode::OnePass::value) {
tracklets.emplace_back(currentSortedIndex, mTimeFrame->getSortedIndex(targetROF, iLayer + 1, iNext), tanL, phi, pivotROF, targetROF);
Expand Down