Error using fminunc in parfor

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Liane Canas 2015-6-2

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https://ww2.mathworks.cn/matlabcentral/answers/222016-error-using-fminunc-in-parfor

评论： Ahmed Nasr 2020-6-10

I used a parfor loop to try reduce the time of the loop. Inside this loop I have another loops, and inside one of these, I call a function to calculate a kernel. This kernel needs another function to minimise the value achieved. To minimise I used the fminunc function. For some loops everything ran well. However, after few iterations (I guess, after a few hundred) the loop is interrupted an e error appears: "Error using lineSearch (line 61): Search direction is not a descent direction; roundoff errors may be affecting convergence." I don't understand what is the problem because for the first loops all was fine. I hope someone with the same issue might be able to help me, or someone with any idea to solve the problem. Regards

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Peter Harrington 2015-9-14

Old bug in MATLAB, many have complained and it still is not fixed in the latest version. Should just give a diagnostic and not exit the script with an error. Because it is caused by roundoff, you run the function a second time and it will execute fine.