Faster CPU backend for large registers (≥ 20 qubits)
还没有人认领这个 Issue。
评估
- 难度
- 5/5
- 预计耗时
- 一周以上
- 新手友好度
- 48/100
- Issue 类型
- 功能
- 描述清晰度
- 基本清楚
- 活跃度
- 活跃
- 技术栈
- rust
- 领域
- performance
调研方向
Start with apply_gate_kernel in src/engine.rs around line 75 and compare its CPU benchmark with Qiskit Aer at 20 or more qubits. The issue lists gate special cases, controlled-gate indexing, cache blocking, and two-qubit fusion as possible optimization paths. Done means CPU circuits run faster without an API change; the issue names no benchmark file or test command.
由索引模型根据 Issue 内容生成。
描述
What you want to do
In the benchmark the CPU backend falls behind Qiskit Aer from 20 qubits (1.17 s vs 431 ms at 22). Each extra qubit costs 3–4× instead of 2× once the 16 MiB state stops fitting in L3 cache. Users without a GPU hit this wall first.
Implementation notes
Ranked roughly by expected gain per line of code:
- Special-case permutation and diagonal gates.
apply_gate_kernel(src/engine.rs:75) runs a
full 2×2 complex multiply for X, CX, Z, CZ, S, T, P and RZ. X and CX only need to swap amplitudes.
Diagonal gates only need to multiply one half (or both halves by a phase). This halves the
arithmetic and the memory writes for diagonal gates. - Controlled gates should only visit pairs whose control bits are set. At the moment the kernel
visits every pair and skips non-matching ones with a branch. Enumerating only the indices that
match turns a full pass into half a pass (CX) or a quarter (CCX). - Cache blocking. Apply runs of gates whose targets are all below some qubit k to one
2^k-amplitude block at a time, so each block stays in L2/L3 while several gates hit it. - Two-qubit fusion. Merge consecutive gates on the same pair of qubits into one 4×4 matrix.
That needs a 4×4 kernel.
What it could look like
No API change: the same circuits just run faster on `backend="cpu"`.
Contributing
- I would like to open a pull request for this (see CONTRIBUTING.md).
- 主要语言
- Rust
- 星标
- 1
- 派生
- 0
- 平均合并
- 12 分钟
- 30 天内合并 PR
- 4
环境准备
- 没有 Dockerfile 或 Docker Compose 文件
- 没有 Pull Request 模板
- 阅读贡献指南
从这里开始
- 先读完整个 Issue，再读项目的贡献指南。
- 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
- Fork 仓库，在一个分支上完成修改。
- 提交 Pull Request，并在描述里引用这个 Issue 编号。
kaiwave/qsengine 的其他 Issue
-
enhancement
难度 2/5 1-3 小时 新手友好度 70/100
-
bug good first issue
难度 2/5 1-3 小时 新手友好度 78/100
-
enhancement
难度 4/5 3-5 天 新手友好度 55/100
-
enhancement
难度 4/5 3-5 天 新手友好度 48/100
-
enhancement
难度 4/5 3-5 天 新手友好度 55/100
相似的 Issue
-
bug order-flow studies ui
难度 2/5 1-3 小时 新手友好度 88/100
userFRM/egui-charts#2417 ·
维护者通常 1 天内回复
-
In a plain-text message, Font, Font Size, Font Color and Text Highlight Color stay live可能已有人在做 @ragelfundionctrumnar 今天认领。 未关闭
难度 2/5 1-3 小时 新手友好度 68/100
UCS-Care-Group/mailcraft#862 ·
维护者通常 1 天内回复
-
难度 2/5 1-3 小时 新手友好度 78/100
smoltcp-rs/smoltcp#1243 ·
维护者通常 1 天内回复
-
bug
难度 2/5 1-3 小时 新手友好度 76/100
维护者通常 4 天内回复
-
难度 2/5 1-3 小时 新手友好度 78/100
维护者通常 1 天内回复