fix: avoid copying map entries in digi cell_hit_map iteration

[Copilot]

Iteration over cell_hit_map was copying each std::pair<uint64_t, MutableRawTrackerHit> unnecessarily.

Changes:

• SiliconTrackerDigi.cc: iterate by const& with structured bindings
• MPGDTrackerDigi.cc: iterate by const& with structured bindings

Before:

for (auto item : cell_hit_map) {
  raw_hits->push_back(item.second);
  if (item.first == sim_hit.getCellID()) {
    // ...
  }
}

After:

for (const auto& [cell_id, hit] : cell_hit_map) {
  raw_hits->push_back(hit);
  if (cell_id == sim_hit.getCellID()) {
    // ...
  }
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>cell_hit_map in MGPD and SiTracker digi loops with copy, not ref</issue_title>
<issue_description>for (auto item : cell_hit_map) copies each entry (including the MutableRawTrackerHit) unnecessarily. Iterating by const& (ideally with structured bindings) avoids extra copies and makes the intent clearer.

Originally posted by @copilot in #2410 (comment)
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes cell_hit_map in MGPD and SiTracker digi loops with copy, not ref #2427

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[Copilot]

Pull request overview

This PR aims to improve performance by avoiding unnecessary copying of map entries during iteration in tracker digitization algorithms. The changes replace value-based iteration (auto item) with const reference iteration using structured bindings (const auto& [cell_id, raw_hit]) for the cell_hit_map loops.

Changes:

• Modified iteration pattern to use const references with structured bindings instead of copying map entries
• Updated variable references from item.first and item.second to clearer cell_id and raw_hit names

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/algorithms/digi/SiliconTrackerDigi.cc	Changed cell_hit_map iteration from copying to const reference with structured bindings
src/algorithms/digi/MPGDTrackerDigi.cc	Changed cell_hit_map iteration from copying to const reference with structured bindings

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[github-actions]

Capybara summary for PR 2428

• rec_dis_10x100_minQ2=0_craterlake_10x100_MT
• rec_dis_10x100_minQ2=1000_craterlake_tracking_only
• rec_dis_18x275_minQ2=0_craterlake_18x275
• rec_dis_18x275_minQ2=0_craterlake_18x275_MT
• rec_dis_18x275_minQ2=0_craterlake_18x275_ST_MT
• rec_dis_18x275_minQ2=1000_craterlake_18x275
• rec_dis_18x275_minQ2=1000_craterlake_18x275_MT
• rec_dis_18x275_minQ2=1000_craterlake_18x275_ST_MT
• rec_dis_5x41_minQ2=0_craterlake_5x41
• rec_e_1GeV_20GeV_craterlake
• rec_pi_1GeV_20GeV_craterlake

Last updated 2026-02-15T10:30-05:00 68b7c95