parallelize and @parameter issue in Mojo 24.5

I am trying to convert my projects to Mojo 24.5. Right now I face the following issue. When running

from algorithm import parallelize

fn main():
    var t = 5
    @parameter
    fn whatever(ip:Int):
        print(t)
    parallelize[whatever](1)

from algorithm import parallelize

fn main():
    var t = 5
    @parameter
    fn whatever(ip:Int):
        print(t)
    parallelize[whatever](1)

I get 4507533440 printed as result. In the @parameter doc https://docs.modular.com/mojo/manual/decorators/parameter it says This is an unsafe feature because we currently do not model the lifetimes of capture-by-reference. but up to 24.4 i never had this issue. Did i miss some fundamental change here? Any advice how to handle this would be great. Thx 🙏 ps adding

  '_ = t'

  '_ = t'

at the end of this demo would solve the issue but that gets complicated and ugly in my projects ...

@parameter | Modular Docs

Executes a function or if statement at compile time.

4 Replies

sora•3mo ago

https://github.com/modularml/mojo/issues/3483#issuecomment-2356009175

GitHub

[BUG] parallelize won't work with local variables (they turn to uni...

Bug description Calling the following code produces garbage values for s and idx: from algorithm import parallelize fn calc(s: Int, h: Int): var s = 5000 var h = 100 @parameter fn worker(y:Int): ...

Martin DudekOP•2mo ago

thanks a lot @sora

sora•2mo ago

I think this is resolved on the latest nightly

Martin DudekOP•2mo ago

thanks @sora , i just tried the little demo i posted with the current nightly (mojo 2024.9.2305 - f7b111af) and yeah, it worked as expected

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parallelize and @parameter issue in Mojo 24.5