Matlab loop closes for no reason at all

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berk can acikgoz 2020-9-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/592777-matlab-loop-closes-for-no-reason-at-all

评论： Image Analyst 2020-9-13

I have a loop as follows:

g=zeros(dim,dim);
for np=1:dim
    b=2*pxHz*phantom(dim);b=b(:,np);
    b=dct(b);
    g(:,np)=dctCoeffs1d*dctGradVect(b,np);
    np
end
figure, imagesc(g),colorbar

and dctGradVect function is as follows:

function g = dctGradVect(b,np)
global imgg imgDistupg imgDistdowng dctCoeffs1d
imgVect=imgg(:,np);distUpVect=imgDistupg(:,np);distDownVect=imgDistdowng(:,np);
fieldVect=dctCoeffs1d*b;
[Ku,Kd]=Kv(fieldVect);
[Ku2,Kd2]=Kv2(fieldVect);
for p=1:length(b)
    for mp=1:length(imgVect)
        matu(p,mp)=trace(diag(dctCoeffs1d(:,p)).*diag(Ku2(mp,:)).*diag(imgVect));
        matd(p,mp)=trace(diag(dctCoeffs1d(:,p)).*diag(Kd2(mp,:)).*diag(imgVect));
    end
end
g=2*real(matu*conj(distUpVect-Ku*imgVect))+2*real(matd*conj(distDownVect-Kd*imgVect));

The loop crashes at some values of np. i.e. crashes at np=10. This crashing point changes every time. Also it gives an error message, some index exceeding some value. However, for a number of iterations this is not the case. What could be the proble? Thx in advance

Edit: imgg, imgDistupg and imgDistdowng are complex dim by dim matrices. dim is fixed and 32 for my case. dctCoeffs1d is a dim by dim matrix again and represents 1d discrete cosine transform.

Edit 2: The loop works fine at first. I mean g is calculated and everything is ok. However, if I run the loop again, it get stuck and MATLAB crashes

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VBBV 2020-9-13

在 MATLAB Online 中打开

What is dim when you create

%if true
  % code
%end
g = zeros(dim,dim)

Is it fixed value or changing ?

May be it's exceeding the limit of one of the vectors in your function

%if true
  % code
%end
function g = dctGradvect(b,np)

Image Analyst 2020-9-13

Looks like you blew right past the posting guidelines that would have enabled a fast answer. Anyway, give us code where we can reproduce it. This means ALL code, even the code that defined the global variables. Also, give the exact error message - ALL THE RED TEXT - but only after you read this link.

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