feat: use npsim -j/--numberOfThreads in workflows

[wdconinc]

Briefly, what does this PR introduce? Please link to any relevant presentations or discussions.

This PR adds -j to the npsim runs in the workflows. Slightly more efficient but more importantly it's functionality we want to ensure is exercised in a place where we can see diffs.

What is the urgency of this PR?

• High (please describe reason below)
• Medium
• Low

What kind of change does this PR introduce?

• Bug fix (issue #__)
• New feature (issue: npsim -j)
• Optimization (issue #__)
• Updated documentation
• other: __

Please check if any of the following apply

• This PR introduces breaking changes. Please describe changes users need to make below.
• This PR changes default behavior. Please describe changes below.
• AI was used in preparing this PR. Please describe usage below.

[Copilot]

Copilot review overview

🟡 Changes recommended

The workflow changes use --numberOfThreads while the PR title/description state the goal is to exercise npsim -j, so the implementation and stated intent should be aligned.

Get a fresh assessment by requesting another Copilot review.

Review effort: Lite
Findings: 1

Open (1)

• Workflow uses --numberOfThreads instead of npsim -j · New

What changed in this PR

This PR updates the CI simulation runs to request multi-threaded execution in npsim, aiming to exercise thread-parallel behavior in a workflow where output diffs are visible.

Changes:

• Add a per-run thread count argument to npsim in the “gun” workflow simulation step.
• Add the same thread count argument to npsim in the DIS workflow simulation step.

File	Description
.github/​workflows/​build-push.yml	Adds CPU-thread-based parallelism configuration to npsim runs in CI workflows.

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[veprbl]

Is that event-by-event reproducible?

[wdconinc]

It is designed to be (that's the part that took the two years; just getting stuff to be multithreaded isn't hard).

[wdconinc]

It is also enforced in DD4hep CI by running test simulations at multiple thread counts and only allowing out-of-order events, but otherwise requiring identity.

[github-actions]

Capybara summary for PR 434

• rec_dis_10x100_minQ2=100_epic_craterlake_amd64 (Δ: 4591) (new artifact) (ref artifact)
• rec_dis_10x100_minQ2=1_epic_craterlake_amd64 (Δ: 4695) (new artifact) (ref artifact)
• rec_dis_18x275_minQ2=100_epic_craterlake_amd64 (Δ: 4749) (new artifact) (ref artifact)
• rec_dis_18x275_minQ2=1_epic_craterlake_amd64 (Δ: 4709) (new artifact) (ref artifact)
• rec_dis_5x41_minQ2=1_epic_craterlake_amd64 (Δ: 4499) (new artifact) (ref artifact)
• rec_dis_5x41_minQ2=1_epic_craterlake_amd64_vs_arm64 (Δ: 4543)
• rec_dis_5x41_minQ2=1_epic_craterlake_arm64 (Δ: 4617) (new artifact) (ref artifact)
• rec_e_1GeV_20GeV_epic_craterlake_amd64 (Δ: 3206) (new artifact) (ref artifact)
• rec_e_1GeV_20GeV_epic_craterlake_amd64_vs_arm64 (Δ: 3152)
• rec_e_1GeV_20GeV_epic_craterlake_arm64 (Δ: 2948) (new artifact) (ref artifact)
• rec_pi_1GeV_20GeV_epic_craterlake_amd64 (Δ: 3048) (new artifact) (ref artifact)
• rec_pi_1GeV_20GeV_epic_craterlake_amd64_vs_arm64 (Δ: 2933)
• rec_pi_1GeV_20GeV_epic_craterlake_arm64 (Δ: 2417) (new artifact) (ref artifact)
• sim_dis_10x100_minQ2=100_epic_craterlake_amd64 (Δ: 418) (new artifact) (ref artifact)
• sim_dis_10x100_minQ2=1_epic_craterlake_amd64 (Δ: 421) (new artifact) (ref artifact)
• sim_dis_18x275_minQ2=100_epic_craterlake_amd64 (Δ: 421) (new artifact) (ref artifact)
• sim_dis_18x275_minQ2=1_epic_craterlake_amd64 (Δ: 421) (new artifact) (ref artifact)
• sim_dis_5x41_minQ2=1_epic_craterlake_amd64 (Δ: 406) (new artifact) (ref artifact)
• sim_dis_5x41_minQ2=1_epic_craterlake_amd64_vs_arm64 (Δ: 408)
• sim_dis_5x41_minQ2=1_epic_craterlake_arm64 (Δ: 421) (new artifact) (ref artifact)
• sim_e_1GeV_20GeV_epic_craterlake_amd64 (Δ: 369) (new artifact) (ref artifact)
• sim_e_1GeV_20GeV_epic_craterlake_amd64_vs_arm64 (Δ: 360)
• sim_e_1GeV_20GeV_epic_craterlake_arm64 (Δ: 347) (new artifact) (ref artifact)
• sim_pi_1GeV_20GeV_epic_craterlake_amd64 (Δ: 328) (new artifact) (ref artifact)
• sim_pi_1GeV_20GeV_epic_craterlake_amd64_vs_arm64 (Δ: 320)
• sim_pi_1GeV_20GeV_epic_craterlake_arm64 (Δ: 284) (new artifact) (ref artifact)
  ^{_{Last updated 2026-10-08T17:11-04:00 72d7bcd}}

[Copilot]

🟢 Approval recommended

The workflow change is minimal, consistent across both npsim invocations, and does not introduce any apparent correctness or CI-configuration issues.

0 open findings

1 resolved since last review

• Workflow uses --numberOfThreads instead of npsim -j

🧠 Review effort: Lite