JuliaLang/julia

`JULIA_NUM_THREADS` ignored when embedding Julia on a Windows system

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#55,468 创建于 2024年8月12日

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bughelp wantedsystem:windows

描述

The following c# code...

Environment.SetEnvironmentVariable("JULIA_NUM_THREADS", "4");
jl_init_with_image__threading(mBinPath, mSysImg);
jl_eval_string("println(\"Threads=$(Threads.nthreads())\")");
jl_eval_string("println(\"JULIA_NUM_THREADS=$(ENV[\"JULIA_NUM_THREADS\"])\")");

Produces the following output

Threads=1
JULIA_NUM_THREADS=4

In discussions with the Jeff and Keno it appears this happens in Windows because there are several environment stores in Windows, and the threads are created by reading with getenv (which access the machine level environment), while later in Julia the ENV is retrieved using getenvw (which access the process level environment).

贡献者指南

技术栈
无
领域
backendapi
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
4
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
half day
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
fresh
清晰度议题是否清楚说明期望改动、验收标准和下一步。
clear
前置要求
Knowledge of Julia's C APIFamiliarity with Windows environment variablesC programming experienceExperience with multithreading
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
25
研究方向
Investigate the Windows environment variable handling in Julia's embedding initialization. The issue mentions that `getenv` reads machine level environment while `getenvw` reads process level. Look at the Julia source code, particularly the thread creation path and the `jl init with image threading` function, to see where `JULIA NUM THREADS` is read. The fix likely involves using the Windows `GetEnvironmentVariable` or ` wgetenv` consistently. Refer to the discussion with Jeff and Keno for further details.