Update each element of multi dimensional array

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bilal javed 2019-4-4

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https://ww2.mathworks.cn/matlabcentral/answers/454312-update-each-element-of-multi-dimensional-array

评论： Walter Roberson 2019-4-18

Hello!

i am working with multi dimensional arrays, and I need to check every combination of values and update them. For this pusrpose, I am using for loops but they are super slow. I have waited hours but it was still processing. Is there any faster way?

My code for 3D array is like this

for i = 1:nrows
    for j = 1:ncols
        for k = 1:ndepths  
            AI = function(a(i), b(j), c(k));
            cspace (i,j,k) = JKM(AI);
        end
    end  
end

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bilal javed 2019-4-17

编辑：bilal javed 2019-4-17

在 MATLAB Online 中打开

Hello !

you were right. Without having a look on actual code, it's hard to solve the problem. I have been working for many days to solve this. Now I new sitiation.

Here function fv is alos using parfor loop. I am using sections to access small part of my large data. But still I am having erro OUT OF MEMORY after 1st iteration.

% Theta ranges
theta1_range = 0:2:360;
theta2_range = 0:2:360;
theta3_range = 0:2:360;
%%%%%%%%%%%%%%%%%%%%%%
nrows = length(theta1_range);
ncols = length(theta2_range);
ndepths = length(theta3_range);
[TH1, TH2, TH3] = ndgrid(theta1_range,theta2_range,theta3_range);
THETA1 = TH1(:);
THETA2 = TH2(:);
THETA3 = TH3(:);
l = length(THETA1);
clear TH1 TH2 TH3
cspace_coords = [THETA1, THETA2, THETA3];
clear THETA1 THETA2 THETA3 theta1_range theta2_range theta3_range
cspace = [];
if (rem(l, 2) == 0)
    sections = round(linspace(0,l,20)); % divide dimension l into small equal parts
else 
    sections = 0:round(l/20):l; % divide dimension l into small equal parts
    if sections(end) ~= l
        sections = round([sections, l]);
    end
end
%%
for i = 1:(length(sections)-1)
    fprintf ('%d of %d\n', i, (length(sections)-1))
    fv = ThreeLinkRobot(DH_para, cspace_coords((sections(i)+1):sections(i+1),:));
    collide = true(length(fv),1);
    parfor j = 1:length(fv)
        collide(j) = GJK(patch(fv(i)),[patch(obstacle1);patch(obstacle2);patch(obstacle3)],10);
    end
    cspace = [cspace; collide];
    clear fv;
end
%%

Guillaume 2019-4-18

The error message tells you the out of memory occurs in the parfor. So, it all depends on that GJK function for which you haven't shown the code.

What's the output of memory before you execute the parfor loop? By far, the biggest variable is your fv which uses ~4.5 GB of memory.

Walter Roberson 2019-4-18

I just noticed that your fv is a struct with fields face and vertices. That suggests that you are creating four patch objects for each of your 296487 struct array elements, and that those form parameters to whatever GJK does. That is a lot of graphics objects, over 72 million verticles for the fv alone, and unknown numbers of graphics elements triggered by the obstacle patches.

Note that graphics objects created on parallel workers cannot change the display: parallel workers are different processes that work independently without connection to the graphics display thread.

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