Isca Reproducibility

ISCA Reproducibility

In architecture, "reproducible" means someone else — or you, three months later, mid-rebuttal — can regenerate every reported number from recorded state. Because most ISCA numbers come out of simulators, reproducibility here is largely configuration archaeology: the result is a function of tool commit, local patches, model parameters, workload build, region selection, and warm-up policy, and losing any one of those breaks the chain. The venue reinforces this culture with post-acceptance artifact evaluation under ACM badging (isca-artifact-evaluation); this skill covers the discipline that must exist before any AE form is filled.

The result chain, and what to pin at each link

One manifest per published number

Adopt the rule that every figure and table in the paper has a manifest and a regeneration command. This is the same manifest format isca-experiments specifies for methodology writing — one artifact serves both purposes.

results/
  f07-headline/
    manifest.ini          # instrument, model, measurement, workloads
    regen.sh              # rebuild -> run -> aggregate -> plot, no hands
    raw/                  # simulator stats as emitted (never edited)
    derived/f07.csv       # scripted aggregation output
    f07.pdf               # exactly the file included in the paper
# The submission-freeze ritual:
git tag isca27-submitted && \
  sha256sum results/*/f*.pdf paper/fig/*.pdf | sort | uniq -c -w64 | \
  awk '$1!=2 {print "FIGURE MISMATCH:", $0}'   # every paper figure must
                                               # hash-match a regenerated one

The freeze ritual catches the classic disaster: a figure in the PDF produced by a config that no longer exists because exploration continued after the plot was made.

Nondeterminism gets measured, not ignored

• Deterministic simulators: verify determinism once (same commit + config + workload → bit-identical stats) and record that check; if a threading mode breaks it, either use the deterministic mode for reported numbers or report dispersion.
• Real hardware: never a single trial. Report median and spread across ≥5 runs, with the machine-state record (governor, turbo, SMT, kernel, isolation measures). Reviewers increasingly ask; artifact evaluators always do.
• Sampled simulation: the sampling procedure and seed are part of the result. Different SimPoint runs are different experiments — archive the chosen regions, don't regenerate them.

Paper-side reporting

The paper must let a skeptical reader reconstruct the setup without the artifact: a full configuration table (structures, sizes, latencies, DRAM timing), the workload list with inputs and build flags summarized, the region/ warm-up policy, and a variability statement wherever hardware was measured. Under double-blind rules the repository link, if given, must be fully anonymized (verified 2026 rule — see isca-submission); the common pattern is an anonymized-mirror link at submission, replaced by the real archival link in the camera-ready.

Resurrectability: the February requirement

The 2026 cycle's rebuttal/revision window (Feb 16 - Mar 6) arrived three months after submission. Teams whose environment had rotted — simulator tree no longer building, cluster images recycled, workload binaries lost — entered the window unable to run the experiments that would have saved the paper. Protocol:

1. At submission: container or environment image built and stored; regen.sh for at least the headline figure verified from the image, not from a dev machine.
2. Window-open minus one week (early February): resurrection drill — boot the image, regenerate one figure end to end, confirm hash match.
3. Keep one team member's environment untouched between November and March; do not upgrade the shared toolchain mid-wait.

Habits that make all of this cheap

• Results directories are append-only; a changed config is a new experiment ID, never an edit in place.
• The plotting path takes experiment IDs, not file paths typed by hand.
• A METHODS.md in the repo grows in real time — every methodological choice (why these regions, why this warm-up, why this DRAM model) written down when made, because November-you will not remember July-you's reasoning.
• Weekly: regen.sh for the current headline figure runs green in CI or by hand. Regeneration that only works on deadline eve doesn't work.

Pre-submission reproducibility gate

• Every paper figure hash-matches a scripted regeneration
• Simulator commit + local patch diff archived alongside results
• Workload binaries/inputs archived or deterministically rebuildable
• Region/checkpoint files stored; sampling seeds recorded
• Hardware numbers carry trial counts and dispersion
• Environment image built, stored, and drill-tested
• Anonymized artifact link (if any) resolves and contains no identity

Where each practice pays off later

Venue facts (AE program, badging, double-blind link rule) verified 2026-07-08 in ../../resources/official-source-map.md; the engineering protocol above is community best practice, applicable regardless of cycle.