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DPL Analysis: First workflow for event mixing (#3450)
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‎Analysis/Tutorials/CMakeLists.txt‎

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SOURCES src/tracksCombinations.cxx
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PUBLIC_LINK_LIBRARIES O2::Framework O2::AnalysisDataModel
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COMPONENT_NAME AnalysisTutorial)
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o2_add_executable(event-mixing
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SOURCES src/eventMixing.cxx
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PUBLIC_LINK_LIBRARIES O2::Framework O2::AnalysisDataModel
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COMPONENT_NAME AnalysisTutorial)

‎Analysis/Tutorials/src/eventMixing.cxx‎

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// Copyright CERN and copyright holders of ALICE O2. This software is
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// distributed under the terms of the GNU General Public License v3 (GPL
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// Version 3), copied verbatim in the file "COPYING".
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//
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// See http://alice-o2.web.cern.ch/license for full licensing information.
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//
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// In applying this license CERN does not waive the privileges and immunities
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// granted to it by virtue of its status as an Intergovernmental Organization
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// or submit itself to any jurisdiction.
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#include "Framework/runDataProcessing.h"
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#include "Framework/AnalysisTask.h"
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#include "Framework/ASoAHelpers.h"
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namespace o2::aod
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{
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namespace hash
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{
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DECLARE_SOA_COLUMN(Bin, bin, int);
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} // namespace hash
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DECLARE_SOA_TABLE(Hashes, "AOD", "HASH", hash::Bin);
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using Hash = Hashes::iterator;
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} // namespace o2::aod
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using namespace o2;
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using namespace o2::framework;
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using namespace o2::soa;
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// This is a tentative workflow to get mixed-event tracks
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// FIXME: this should really inherit from AnalysisTask but
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// we need GCC 7.4+ for that
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struct HashTask {
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std::vector<float> xBins{-1.5f, -1.0f, -0.5f, 0.0f, 0.5f, 1.0f, 1.5f};
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std::vector<float> yBins{-1.5f, -1.0f, -0.5f, 0.0f, 0.5f, 1.0f, 1.5f};
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Produces<aod::Hashes> hashes;
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// Calculate hash for an element based on 2 properties and their bins.
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int getHash(std::vector<float> const& xBins, std::vector<float> const& yBins, float colX, float colY)
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{
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for (int i = 0; i < xBins.size(); i++) {
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if (colX < xBins[i]) {
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for (int j = 0; j < yBins.size(); j++) {
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if (colY < yBins[j]) {
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return i + j * (xBins.size() + 1);
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}
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}
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// overflow for yBins only
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return i + yBins.size() * (xBins.size() + 1);
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}
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}
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// overflow for xBins only
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for (int j = 0; j < yBins.size(); j++) {
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if (colY < yBins[j]) {
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return xBins.size() + j * (xBins.size() + 1);
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}
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}
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// overflow for both bins
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return (yBins.size() + 1) * (xBins.size() + 1) - 1;
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}
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void process(aod::Collisions const& collisions)
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{
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for (auto& collision : collisions) {
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int hash = getHash(xBins, yBins, collision.posX(), collision.posY());
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LOGF(info, "Collision: %d (%f, %f, %f) hash: %d", collision.index(), collision.posX(), collision.posY(), collision.posZ(), hash);
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hashes(hash);
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}
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}
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};
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// Version 1: Using categorised combinations
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struct CollisionsCombinationsTask {
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void process(aod::Hashes const& hashes, aod::Collisions& collisions, aod::Tracks& tracks)
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{
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collisions.bindExternalIndices(&tracks);
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auto tracksTuple = std::make_tuple(tracks);
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AnalysisDataProcessorBuilder::GroupSlicer slicer(collisions, tracksTuple);
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// Strictly upper categorised collisions
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for (auto& [c1, c2] : selfCombinations("fBin", join(hashes, collisions), join(hashes, collisions))) {
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LOGF(info, "Collisions bin: %d pair: %d (%f, %f, %f), %d (%f, %f, %f)", c1.bin(), c1.index(), c1.posX(), c1.posY(), c1.posZ(), c2.index(), c2.posX(), c2.posY(), c2.posZ());
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auto it1 = slicer.begin();
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auto it2 = slicer.begin();
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for (auto& slice : slicer) {
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if (slice.groupingElement().index() == c1.index()) {
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it1 = slice;
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break;
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}
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}
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for (auto& slice : slicer) {
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if (slice.groupingElement().index() == c2.index()) {
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it2 = slice;
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break;
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}
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}
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auto tracks1 = std::get<aod::Tracks>(it1.associatedTables());
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tracks1.bindExternalIndices(&collisions);
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auto tracks2 = std::get<aod::Tracks>(it2.associatedTables());
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tracks2.bindExternalIndices(&collisions);
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for (auto& [t1, t2] : combinations(CombinationsFullIndexPolicy(tracks1, tracks2))) {
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LOGF(info, "Mixed event tracks pair: (%d, %d) from events (%d, %d)", t1.index(), t2.index(), c1.index(), c2.index());
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}
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}
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}
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};
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// Version 2: Filtering instead of combinations
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// Possible only after filters & grouping upgrades
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// struct CollisionsFilteringTask {
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// Alternatively: filter/partition directly on collisions
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// expressions::Filter aod::hash::bin{0} == aod::hash::bin{1};
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// Currently multiple grouping and grouping by Joins is not possible
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// void process(soa::Filtered<soa::Join<aod::Hashes, aod::Collisions>>::iterator const& hashedCol1, aod::Tracks const& tracks1,
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// soa::Filtered<soa::Join<aod::Hashes, aod::Collisions>>::iterator const& hashedCol2, aod::Tracks const& tracks2)
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//{
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// for (auto& [t1, t2] : combinations(CombinationsFullIndexPolicy(tracks1, tracks2))) {
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// LOGF(info, "Mixed event tracks pair: (%d, %d) from events (%d, %d)", t1.index(), t2.index(), hashedCol1.index(), hashedCol2.index());
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// }
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//}
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// };
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// What we would like to have
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struct MixedEventsTask {
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void process(aod::Collision const& col1, aod::Tracks const& tracks1, aod::Collision const& col2, aod::Tracks const& tracks2)
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{
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for (auto& [t1, t2] : combinations(CombinationsFullIndexPolicy(tracks1, tracks2))) {
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LOGF(info, "Mixed event tracks pair: (%d, %d) from events (%d, %d)", t1.index(), t2.index(), col1.index(), col2.index());
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}
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}
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};
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WorkflowSpec defineDataProcessing(ConfigContext const&)
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{
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return WorkflowSpec{
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adaptAnalysisTask<HashTask>("collisions-hashed"),
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adaptAnalysisTask<CollisionsCombinationsTask>("mixed-event-tracks")};
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}

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