using variables in a parfor loop
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Marc Laub el 9 de Nov. de 2019
Hey, I am very new to the parallel computing and i got some trouble.
So basicly i have so example code very similar to this one:
a = (normrnd(1,1,[100000,1]))+5;
Inside the nested for loop are many more alculations which takes a huge amount of time, so i basically want to cut a into as much pieces as i have physical cores, so in this case 4 *20000 and then do the same calculations of thos 20000 arrays parrallel.
But I direclty get some error cause i cannot use my input variable from outside the parfor loop because of classification (Code without the outside while loop)
Shouldnt my input d (20000x4 array) not work as an broadcast variable as defined in https://de.mathworks.com/help/parallel-computing/troubleshoot-variables-in-parfor-loops.html ?
Or am I missanderstanding something very basic in parallel computing?
Many thanks in advance
Daniel M el 9 de Nov. de 2019
I think it's because you're using d as the source and the sink in your loop, and you're assigning to d in a way that can make practically anything happen to the size of d, on different iterations. For example, what if on the first iteration d(:,i) contains no zeros, but on the second one it contains all zeros. Then 1:length(v) is changing every iteration and makes assignment to d impossible to determine a priori.