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Faster weight calculation - #126
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Pull request overview
Improves ppvm-runtime truncation performance by speeding up Pauli “weight” computation (hot in MaxPauliWeight/MaxLossWeight truncation) and by skipping retain passes entirely when the truncation is effectively disabled via a sentinel. Adds Rust/Python/Julia benchmarks to reproduce/track the regression described in the PR.
Changes:
- Optimized
PauliWordTrait::weight()(and lossy variants) to popcount directly over raw storage bytes usingbytemuck. - Avoided unnecessary
retain()passes whenMaxPauliWeight(usize::MAX)/MaxLossWeight(usize::MAX)is used to opt out of those truncations. - Added benchmarking coverage (Criterion bench + pytest-benchmark + Julia mirrors) and wired pytest-benchmark into the Python dev environment.
Reviewed changes
Copilot reviewed 16 out of 18 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
crates/ppvm-runtime/src/word/data.rs | Fast popcount-based Pauli weight computation over raw storage bytes. |
crates/ppvm-runtime/src/loss/data.rs | Same optimization for lossy words (weight + loss_weight). |
crates/ppvm-runtime/src/strategy.rs | Early-return optimization when max-weight truncation is disabled via usize::MAX. |
crates/ppvm-runtime/src/traits/coefficient.rs | Adds #[inline] hints to cutoff methods used during truncation retains. |
crates/ppvm-runtime/benches/trotter.rs | Updates trotter benchmark strategy to match Python binding configuration and thread settings. |
crates/ppvm-runtime/benches/truncation-weight.rs | New Criterion micro-benchmark focusing on truncation strategy costs. |
crates/ppvm-runtime/Cargo.toml | Registers the new truncation-weight benchmark target. |
ppvm-python/pyproject.toml | Adds pytest-benchmark to the dev group and disables benchmarking by default via pytest addopts. |
ppvm-python/uv.lock | Lockfile update for pytest-benchmark (and its dependency py-cpuinfo). |
ppvm-python/test/benchmarks/test_trotter.py | New pytest-benchmark mirror of the Rust trotter bench for Python bindings. |
ppvm-python/demo/trotter_ladder.py | New pedagogical/demo script showing a truncation-controlled ladder Trotter example. |
ppvm-python/demo/stim_demo.py | New demo script for running/sampling Stim programs via Python bindings. |
julia-benchmarks/benches/truncation-weight.jl | Julia-side mirror of the new Rust truncation-weight benchmark. |
julia-benchmarks/benches/trotter.jl | Adjusts gate order to better align with Heisenberg vs Schrödinger ordering assumptions. |
julia-benchmarks/benches/random-circuit.jl | Aligns circuit construction/benchmark semantics with the Rust benchmark (no truncation). |
julia-benchmarks/benches/gates.jl | Minor adjustments to which qubits are targeted by rotation benchmarks. |
julia-benchmarks/xy_ladder_msd.jl | New Julia script for MSD XY-ladder benchmark comparison vs ppvm. |
julia-benchmarks/Manifest.toml | Large lockfile update to support the Julia benchmark additions/updates. |
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AlexSchuckert added a commit
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Jun 17, 2026
…shim Brings the bytemuck-based weight() speedup + early-return for uncapped MaxPauliWeight (and the rest of #126) into the Lindblad branch. Conflicts resolved: keep stim_demo.py (byte-identical to lindblad-shim's stim_msd.py rename); regenerate uv.lock against the merged pyproject. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
AlexSchuckert added a commit
that referenced
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Jun 17, 2026
…merging Brings the bytemuck-based weight() speedup + early-return for uncapped MaxPauliWeight (and the rest of #126) into the symmetry-merging branch. Conflicts resolved: keep stim_demo.py (byte-identical to the stim_msd.py rename); regenerate uv.lock against the merged pyproject. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
AlexSchuckert added a commit
that referenced
this pull request
Jun 17, 2026
The expm serial/parallel SpMV parity test built `ExpmOpts { tol,
parallel_threshold }` without the `max_krylov_m` field, so `cargo test`
failed to compile the ppvm-lindblad test target (pre-existing on
lindblad-shim, surfaced when running the full suite after merging #126).
The whole Rust workspace test suite now passes.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
david-pl
enabled auto-merge (squash)
June 19, 2026 08:09
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Benchmarking trotter including a
MaxPauliWeighttruncation strategy showed a major regression. This PR usesbytemuckto bypass thebitvecmethods and directly computes the weight from the total&[u8]slices of bits.