Fix Track Sharing in PHSimpleVertexFinder by adeebsaed · Pull Request #4444 · sPHENIX-Collaboration/coresoftware

adeebsaed · 2026-09-17T23:16:49Z

The original findConnectedTracks implementation used a single scan of the track-pair map to extend each connected group. During that scan, a pair could add tracks to the group when at least one of its tracks was already present. However, a pair rejected earlier because neither track belonged to the group was not reconsidered after subsequent pairs expanded the group. Consequently, the group could be finalized before all indirectly connected tracks had been included, making the grouping dependent on the order in which pairs were visited.

For example, consider a group initially containing tracks A and B. If the scan encounters the pair C–D before B–C, it initially skips C–D. The later pair B–C adds C, making C–D eligible to extend the group, but the single scan never returns to it. Track D therefore remains outside the group despite being connected to A and B through C. Subsequent grouping can then produce overlapping groups that share tracks, contributing to track sharing between vertex candidates.

This change wraps the existing inner pair scan in a loop that repeats until a complete scan adds no new tracks. At the start of each pass, the size of the connected set is recorded. After the pass, the scan is repeated only if that size has increased. This allows previously skipped pairs to be reconsidered as the group grows and follows indirect connections until no further expansion is possible. Because connected is a set, inserting tracks already present does not increase its size or unnecessarily prolong the loop. The finite number of available tracks guarantees termination.

The modification is confined to repeating the existing inner scan and checking whether the connected set has grown. The existing pair-selection conditions, track insertions, used bookkeeping, and group-finalization logic are retained. No reconstruction cuts or downstream vertex-position calculations are changed. The fix addresses incomplete connected-group construction.

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Types of changes

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to not work for users)
Requiring change in macros repository (Please provide links to the macros pull request in the last section)
I am a member of GitHub organization of sPHENIX Collaboration, EIC, or ECCE (contact Chris Pinkenburg to join)

What kind of change does this PR introduce? (Bug fix, feature, ...)

TODOs (if applicable)

Links to other PRs in macros and calibration repositories (if applicable)

track_sharing_pull_request_plots.pdf

Uploading SAED_PPG_07_25_2026.pdf…

Motivation / Context

This change fixes primary track sharing in PHSimpleVertexFinder. It ensures that chained track connections form complete connected groups.

Key Changes

findConnectedTracks now repeats the pair scan until a full scan adds no tracks.
Existing pair-selection conditions remain unchanged.
No public interface or I/O format changes were made.

Potential Risk Areas

Reconstruction output can change for chained track connections.
Repeated scans can increase processing time for large track groups.
No thread-safety impact is indicated.

Possible Future Improvements

Add regression tests for multi-step track-sharing chains.
Measure performance for high track multiplicities.

Test results were not provided. AI-generated summaries can contain mistakes; verify this summary against the implementation and validation results.

coderabbitai · 2026-09-17T23:17:04Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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offline/packages/trackreco/PHSimpleVertexFinder.cc

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📝 Walkthrough

Walkthrough

findConnectedTracks now rescans the track-pair map until no new track joins the connected set. This resolves chained connections before the set is closed and emitted as a vertex.

Changes

Track connection resolution

Layer / File(s)	Summary
Repeat pair scans until convergence `offline/packages/trackreco/PHSimpleVertexFinder.cc`	`findConnectedTracks` repeats pair-map scans while the connected set grows. The scan stops when its size remains unchanged.

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to 3157e

This change completes chained track grouping while preserving existing selection behavior, with no material merge-blocking risk identified.

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sphenix-jenkins-ci · 2026-09-18T06:06:50Z

Build & test report

Report for commit 3157e7f6f87f65ea82fc7a5d440a2ca962d379b6:

builds and tests overall are SUCCESS.
Build with configuration of alma9.2-gcc-14.2.0 / clang is SUCCESS, 📊clang report (full)/(new), build log
Build with configuration of alma9.2-gcc-14.2.0 / new is SUCCESS, 📊Compiler report (full)/(new), build log
- Generating DST and readback: build is SUCCESS
- Calorimeter QA: build is SUCCESS, 📊 trends
  - 📊 QA-calorimeter for e- at p_T=4GeV : combined Chi2/nDoF = 49.8894 / 72, and combined p-Value = 0.978165
  - 📊 QA-calorimeter for pi+ at p_T=30GeV : combined Chi2/nDoF = 34.6977 / 72, and combined p-Value = 0.99994
  - 📊 QA-calorimetric-jet for e- at p_T=4GeV : combined Chi2/nDoF = 89.0492 / 42, and combined p-Value = 3.12982e-05
  - 📊 QA-calorimetric-jet for pi+ at p_T=30GeV : combined Chi2/nDoF = 15.0901 / 42, and combined p-Value = 0.999958
- Tracking QA with Distortions: build is SUCCESS, 📊 trends
  - 📊 QA-distortions
- Tracking QA at low occupancy: build is SUCCESS, 📊 trends
  - 📊 QA-Intt : combined Chi2/nDoF = -0 / 72, and combined p-Value = 1
  - 📊 QA-Micromegas : combined Chi2/nDoF = -0 / 20, and combined p-Value = 1
  - 📊 QA-Mvtx : combined Chi2/nDoF = -0 / 54, and combined p-Value = 1
  - 📊 QA-Tpc : combined Chi2/nDoF = -0 / 56, and combined p-Value = 1
  - 📊 QA-tracking : combined Chi2/nDoF = -0 / 56, and combined p-Value = 1
  - 📊 QA-vertexing : combined Chi2/nDoF = 30 / 112, and combined p-Value = 1
- Tracking QA for Pythia D0-jet: build is SUCCESS, 📊 trends
  - 📊 QA-Intt : combined Chi2/nDoF = -0 / 72, and combined p-Value = 1
  - 📊 QA-Micromegas : combined Chi2/nDoF = -0 / 20, and combined p-Value = 1
  - 📊 QA-Mvtx : combined Chi2/nDoF = -0 / 54, and combined p-Value = 1
  - 📊 QA-Tpc : combined Chi2/nDoF = -0 / 56, and combined p-Value = 1
  - 📊 QA-tracking : combined Chi2/nDoF = -0 / 50, and combined p-Value = 1
  - 📊 QA-vertexing : combined Chi2/nDoF = 30 / 112, and combined p-Value = 1
- Tracking QA runnumber 53877: build is SUCCESS, 📊 trends
  - 📊 QA-intt : combined Chi2/nDoF = -0 / 18, and combined p-Value = 1
  - 📊 QA-micromegas : combined Chi2/nDoF = -0 / 6, and combined p-Value = 1
  - 📊 QA-mvtx : combined Chi2/nDoF = -0 / 18, and combined p-Value = 1
  - 📊 QA-siliconseeds : combined Chi2/nDoF = 3.3382e-07 / 20, and combined p-Value = 1
  - 📊 QA-tpc : combined Chi2/nDoF = -0 / 48, and combined p-Value = 1
  - 📊 QA-tpcseeds : combined Chi2/nDoF = -0 / 28, and combined p-Value = 1
  - 📊 QA-trackfit : combined Chi2/nDoF = -0 / 32, and combined p-Value = 1
- Tracking QA runnumber 79513: build is SUCCESS, 📊 trends
  - 📊 QA-intt : combined Chi2/nDoF = -0 / 18, and combined p-Value = 1
  - 📊 QA-micromegas : combined Chi2/nDoF = -0 / 6, and combined p-Value = 1
  - 📊 QA-mvtx : combined Chi2/nDoF = -0 / 18, and combined p-Value = 1
  - 📊 QA-siliconseeds : combined Chi2/nDoF = -0 / 20, and combined p-Value = 1
  - 📊 QA-tpc : combined Chi2/nDoF = -0 / 48, and combined p-Value = 1
  - 📊 QA-tpcseeds : combined Chi2/nDoF = -0 / 28, and combined p-Value = 1
  - 📊 QA-trackfit : combined Chi2/nDoF = -0 / 32, and combined p-Value = 1
- system alma9.2-gcc-14.2.0, build new: run the default sPHENIX macro: build is SUCCESS, output, trends 📊
- system alma9.2-gcc-14.2.0, build new: run the default CaloProduction/Fun4All_Year2.C macro: build is SUCCESS, output, trends 📊
- system alma9.2-gcc-14.2.0, build new: Valgrind test of CaloProduction/Fun4All_Year2.C: build is SUCCESS, 📊valgrind report, trends 📊
- system alma9.2-gcc-14.2.0, build new: Valgrind test of CaloProduction/Fun4All_Year2_Fitting.C: build is SUCCESS, 📊valgrind report, trends 📊
- system alma9.2-gcc-14.2.0, build new: run the overlap check for sPHENIX macro: build is SUCCESS, output
- system alma9.2-gcc-14.2.0, build new: Valgrind test: build is SUCCESS, 📊valgrind report, trends 📊
Build with configuration of alma9.2-gcc-14.2.0 / scan is SUCCESS, 📊scan-build report (full)/(new), build log
clang-tidy is SUCCESS, 📊clang-tidy report (full)/(new)
cpp-check is SUCCESS, 📊cppcheck report (full)/(new)