Groups   26 of 99+      julia-users ›  parallel , double loop , what wrong? 7 posts by 3 authors      paul analyst    10 11 15   Like here , what wrong ? k 100 mapa zeros k,k   julia   parallel for i 1:k,j 1:k        mapa i,j  sqrt sum  D i,: -D j,:  . 2          end ERROR: syntax: invalid assignment location  Paul     Daniel Arndt    10 11 15   It appears that the multiple for loop syntax isn't supported for  parallel ... I found this issue: https:  github.com JuliaLang julia issues 10109  I'm brand new to Julia, so take this warning with that in mind, but I would also be cautious writing to  mapa  inside your parallel for loop, as each process will have a different copy of the Array, as described here in the documentation: http:  julia.readthedocs.org en latest manual parallel-computing  parallel-map-and-loops  Cheers, Dan      Vincent Lostanlen    10 12 15    Dear Paul,  For k 100 and your purpose, parallelization may not be the utmost performance bottleneck here. I advise you to use the Distances-jl package. Since Julia stores contiguous memory in column-major order, you will first need to transpose the matrix D — or, better, to define it foremost as a n k matrix instead of k n. Once you've ensured that, calling mapa   Distances.pairwise Euclidean  , D   should give you at least a 100x speedup over the for loop you've written, so parallelization should no longer be necessary. Vincent.      paul analyst    10 12 15  Re:  julia-users  Re:  parallel , double loop , what wrong?  Big THX Vincent , big help :  Paul W dniu 2015-10-12 o 12:23, Vincent Lostanlen pisze:      paul analyst    10 12 15  Re:  julia-users  Re:  parallel , double loop , what wrong?  Unfortunaty for big file no memory :   julia  F1 load  F.jd , F   283300x266 Array Float64,2 : julia  mapa   Distances.pairwise Euclidean  , F1'  ERROR: OutOfMemoryError   in pairwise at C:\Users\SAMSUNG2\.julia\v0.4\Distances\src\generic-jl:132  Do You have any hint for big sets ?   Paul  W dniu 2015-10-12 o 12:23, Vincent Lostanlen pisze:        Vincent Lostanlen    10 12 15  Re:  julia-users  Re:  parallel , double loop , what wrong?  Dear Paul, Remember that for K 283300, you’ll have K  K+1  2   4.0e10 distance values.  That is over 160 gigabytes in memory. The reason you have an OOM error is that this exceeds the RAM of your machine. So consider whether you really need a quadratic algorithm on such a large number of samples. If so, you’ll have to carefully split the dataset in P 10 splits, and then call Distances.pairwise over all splits p and q for all p    q    P while progressively freeing memory. That will be P  P+1  2   55 iterations, each of them allocating 1.6 Gb. Store progressively each of these 55 gigabyte-sized matrices in your hard drive.  Do you really need all distance values ? If your final application is e.g. clustering, there are suboptimal large-scale algorithms that have a lower complexity.  Vincent.      paul analyst    10 12 15  Re:  julia-users  Re:  parallel , double loop , what wrong?  Thx, huge help:  unfortunatly i must compute all ;  bur only one time ;   Paul W dniu 2015-10-12 o 20:52, Vincent Lostanlen pisze: