Make stim sampling parallel by default by david-pl · Pull Request #108 · QuEraComputing/ppvm

david-pl · 2026-06-08T10:19:51Z

This PR updates ppvm-stim multi-shot sampling so that (when compiled with the optional rayon feature) it automatically uses parallel execution for large shot batches, and updates the Rust/Python user-facing docs + tests to reflect the new "shot-indexed factory" API and deterministic seeding strategy.

Changes

Refactors Stim sampling to support sample_serial, sample_parallel (rayon-gated), and a default sample that chooses serial vs parallel based on batch size and thread count.
Updates Rust examples/docs/tests to use a factory closure Fn(usize) -> GeneralizedTableau (shot index provided for deterministic per-shot seeds).
Enables rayon-backed sampling in the Python native extension and adds Python/Rust tests for reproducibility and serial/parallel equivalence.
Splits sample into two #[cfg]-gated definitions so non-rayon builds do not require Sync on the factory closure.
Renames prepare → validate and execute_prepared → execute_validated throughout for naming clarity.
Adds sample_serial_validated, sample_parallel_validated, and sample_validated variants that accept pre-validated &[ExtendedInstruction] + measurement_count and skip re-validation. The Python sample() binding uses sample_validated() so validation runs only once at StimProgram.parse() time instead of on every sampling call.
Documents that per-shot seeds use wrapping (mod 2⁶⁴) arithmetic.

Copilot

Pull request overview

This PR updates ppvm-stim multi-shot sampling so that (when compiled with the optional rayon feature) it automatically uses parallel execution for large shot batches, and updates the Rust/Python user-facing docs + tests to reflect the new “shot-indexed factory” API and deterministic seeding strategy.

Changes:

Refactors Stim sampling to support sample_serial, sample_parallel (rayon-gated), and a default sample that chooses serial vs parallel based on batch size and thread count.
Updates Rust examples/docs/tests to use a factory closure Fn(usize) -> GeneralizedTableau (shot index provided for deterministic per-shot seeds).
Enables rayon-backed sampling in the Python native extension and adds Python/Rust tests for reproducibility and serial/parallel equivalence.

Reviewed changes

Copilot reviewed 10 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
skills/ppvm-usage/SKILL.md	Updates user documentation for the new shot-indexed factory and parallel sampling behavior.
skills/ppvm-usage/examples/rust/src/bin/stim_sample.rs	Updates example to use the new factory closure signature and explains deterministic seeding.
ppvm-python/test/generalized_tableau/test_stim.py	Adds a reproducibility test intended to cover the parallel sampling path.
ppvm-python/src/ppvm/generalized_tableau.py	Documents parallel sampling semantics and deterministic `seed + i` behavior.
crates/ppvm-stim/tests/executor.rs	Updates sampling tests for the new factory signature and adds serial-vs-parallel equivalence test (rayon).
crates/ppvm-stim/src/lib.rs	Re-exports `sample_serial` and (feature-gated) `sample_parallel`; updates doc example.
crates/ppvm-stim/src/executor.rs	Implements `sample_serial`, `sample` auto-dispatch, and `sample_parallel` (rayon).
crates/ppvm-stim/Cargo.toml	Adds optional `rayon` feature/dependency.
crates/ppvm-python-native/src/interface_tableau.rs	Routes Python sampling through `ppvm_stim::sample` with per-shot deterministic seeding and GIL release.
crates/ppvm-python-native/Cargo.toml	Enables `ppvm-stim`’s `rayon` feature for the Python native extension.
Cargo.lock	Records `rayon` as a dependency of `ppvm-stim`.
.gitignore	Ignores `/debug`.

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github-actions · 2026-06-08T10:32:22Z

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Pull request overview

Copilot reviewed 10 out of 12 changed files in this pull request and generated 3 comments.

…ute_validated; add validated sample variants - Rename prepare.rs -> validate.rs and function prepare() -> validate() - Rename execute_prepared() -> execute_validated() throughout - Add sample_serial_validated / sample_parallel_validated / sample_validated that skip re-validation for callers that already hold a validated program - Python binding sample() now uses sample_validated() via the pre-validated StimProgram, avoiding redundant re-validation on every sampling call - Update test file prepare.rs -> validate.rs - Update all doc comments and unreachable! messages

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crates/ppvm-stim/src/validate.rs:21

validate() currently only checks probability ranges for measurement instructions and MPAD, but it does not validate probabilities for noise instructions (e.g. DEPOLARIZE1(p), X_ERROR(p), etc.) nor for I_ERROR[loss]/[correlated_loss]. This means invalid probabilities like DEPOLARIZE1(2.0) can pass validation and then be executed, despite ExecError::InvalidProbability existing for this purpose.

…ngs; update AGENTS.md and dev guide with docstring convention

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Pull request overview

Copilot reviewed 17 out of 19 changed files in this pull request and generated 1 comment.

Merging main (#101 classical mixtures + sampling) added a `T::Coeff: PartialOrd` bound to `execute_validated`, but the `sample_serial_validated`, `sample`, `sample_validated`, and `sample_parallel*` wrappers only carried `PartialOrd<f64>`, so the crate stopped compiling. Add the missing `+ PartialOrd` to all seven affected functions. Also resolve outstanding review feedback: - Disambiguate the `[validate]` intra-doc links (now ambiguous between the `validate` module and `validate` fn after the prepare->validate rename) via the `fn@` disambiguator, silencing the rustdoc warning. - Rename `test_sample_stim_seeded_is_reproducible_across_the_parallel_path` -> `..._for_large_batches` and reword the comment: it asserts reproducibility whether rayon runs the batch serially or in parallel (the cutoff depends on pool size, which the test does not control). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Make stim sampling parallel by default

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Merge branch 'main' into david/stim-rayon

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Merge branch 'main' into david/stim-rayon

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Roger-luo merged commit 2de425e into main Jun 20, 2026
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