Shared Array values not updating when using @parallel

Question

I am trying to create a parallel for loop using @parallel, in order to compute a cumulative sum of a SharedArray. A simple test I'm running looks like this:

p = SharedArray{Float64}(10,10);

@parallel for i = 1 : 5
    p = p .+ 1
end

p

However, when printing p, I just get a series of zeros, as if the for loop never happened. I have tested that the code actually enters the for loop by having it print on each loop.

I realize that this question may possibly have a straightforward answer to many people, but following the Julia manual and looking for answers online has not lead me to a solution so far.

Thanks in advance,

Simos

James Cook · Accepted Answer · 2018-06-05 09:51:30Z

0

Does changing the = operator .= have the desired outcome?

@parallel for i = 1 : 5
    p .= p .+ 1
end

edit: formatting.

answered Jun 5, 2018 at 9:51

James Cook

1601 silver badge6 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Simos Papadimitropoulos Over a year ago

Yes, that seemed to to the trick, thank you! Would be glad to know why this operator changes the result so drastically, since it has no effect when doing calculations in the serial version of the code.

Collectives™ on Stack Overflow

Shared Array values not updating when using @parallel

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related