get matrix in parfor

Dear all,

I have this code

result=[]
for m=1:10
   for k=1:100
      for c=1:50
        a=m+k*c;
        b=m*k-c;
        result=[result;a b];
      end
    end
end
I try to convert from for to parfor like this

result=[]
for m=1:10
   parfor k=1:100
      for c=1:50
        a=m+k*c;
        b=m*k-c;
        result=[result;a b];
      end
    end
end

But there is a problem, "the variable 'result' used a value outside of the loop". I has searched from the site, but i'm not understand about the solution.

How can I fix it.

Answer 1

[Edric Ellis]

You can't update the parfor reduction variable result inside the inner loop, you need to update it directly in the body of the parfor loop. You can work around this by making a new temporary reduction variable for each iteration of the parfor loop, and then update result once that's complete, like so:

result=[];
for m=1:10
    parfor k=1:100
        tmp = [];
        for c=1:50
            a=m+k*c;
            b=m*k-c;
            tmp=[tmp;a b];
        end
        result = [result; tmp];
    end
end