Parfor loop stuck when saving plots

Question

Alexandre 2023-10-23

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2037356-parfor-loop-stuck-when-saving-plots

评论： Rik 2023-10-25

Hello everyone,

I am encountering a strange issue when using a parfor loop to perform calculations on a set of data and saving the plots.

I used to do this for my files and to plot and save multiples data (2D data of electrical field, 1D profile, FWHM size as function of the file, etc) and I never had any issue.

However, I recently try to do the same for a 3D plot (using surface function) and then the parfor loop does not respond and stop doing anything (but still my CPU is 100 %...). It happens wether I used 1 or 16 (my max) workers, and in 2 differents PC with R2020a.

While debugging, the issue is coming from the print (or saveas, I tried both) command...but this happened only for the full size of my data (X, Y and E are 2000x2000, with each a 32 MB size) ; if I plot for example only 300x300 points it works. [Furthermore I have up to 128 GB of RAM memory and never more than 20 GB is used)

I also try to plot 600x600 with 1 worker or 300x300 with 16 workers and the first case is blocked while the second one works. Also, if I put a condition in my loop so that the saving is done only in the first case (k=1), then every workers are running except the one that met that condition. What is more, if I change X and Y to a 1D array (1x2000) and keep E 2D (2000x2000), then a imagesc plot is working without issue, so there is no issue with my data I believe.

And, of course, if I run the same code with a normal for loop, everything goes well (but very slooooow !)

I have no more ideas about that, so if you have some suggestions I will be glad :)!

Here is an example of my code:

myfolder = pwd;
destdirectory = [pwd,'/3Dsave'];
mkdir(destdirectory); 
L = dir('./*dat');
parfor k=1:length(L)
    cd(myfolder)
    pause(0.01);
    N = L(k).name;
    Md = table2array(readtable(N)); 
    x = Md(:,1);
    nx = length(unique(x));
    
    
    y = Md(:,2);
    ny = length(unique(y));
    
    yl = reshape(y,[nx,ny]);
    xl = reshape(x,[nx,ny]);
    Ez = Md(:,3);
    Ez2 = reshape(Ez,[nx,ny]);
    Ez2=abs(Ez2.^2);
    
    fl=figure('visible','off');
    surface(xl*1e6,yl*1e6,Ez3)
    shading interp
    colormap jet
    set(gca,'FontSize',11,'fontweight','bold')
    hcb=colorbar;
    hcb.Title.String = "A_0^2";
    title(N)
    cd(destdirectory)
    pause(0.01)
    print(['iml_',num2str(k),'_apng'],'-dpng','-r1200')
    close(fl);
end

4 个评论
显示 2更早的评论隐藏 2更早的评论

Walter Roberson 2023-10-25

length(A(1,:)) is significantly less efficient than size(A,2) . A(1,:) has to first extract all of row 1 from the matrix, even though the row elements are not going to be in consecutive memory (unless it just happened to be a vector). This results in a bunch of unnessary memory copying.

length(A(1,:)) also fails if A has no rows, such as if it A were 0 x 10 . You would get an error rather than either 0 or 10.

size() is one of the very fastest operations for any class that does not override the definition of the size() method: it only has to look at the header block for the expression. ( sym is an example of a class that redefines size. )

Rik 2023-10-25

For the graphics handles I meant you should specify the parent object in every call that supports it. Perhaps that will help.

请先登录，再进行评论。

请先登录，再回答此问题。

Parfor loop stuck when saving plots

4 个评论
显示 2更早的评论隐藏 2更早的评论

回答（0 个）

另请参阅

类别

标签

产品

版本

Community Treasure Hunt

Parfor loop stuck when saving plots

4 个评论 显示 2更早的评论隐藏 2更早的评论

回答（0 个）

另请参阅

类别

标签

产品

版本

Community Treasure Hunt

4 个评论
显示 2更早的评论隐藏 2更早的评论