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parfor results core dump

Asked by Zoltán Csáti on 7 Nov 2017
Latest activity Commented on by Zoltán Csáti on 18 Nov 2017
MATLAB R2015b crashes on 64 bit Linux. I managed to track the cause of failure to this chunk of code
values = cell(1, nElement);
parfor i = 1:nElement
values{i} = element(i).stiffnessMatrix;
end
where element is an object array and I call the stiffnessMatrix method on all of the objects. In practice nElement is very big. The segfault comes from libtbbmalloc.so.2 (now I know that parfor wraps TBB).
Reading on forums, I preloaded the problematic libraries:
export LD_PRELOAD=/usr/local/MATLAB/R2015b/bin/glnxa64/libtbb.so.2:/usr/local/MATLAB/R2015b/bin/glnxa64/libtbbmalloc.so.2
In vain. The same error persists. It seem that TBB cannot allocate memory (for smaller problem, parfor works). Why does it work for the simple for loop and not for the parfor loop? Just before the program crashed, I saw that I have 11 GB of free memory (more than 4 times more than used by the whole operating system).
I tested it on Windows, and it still fails with the same error. Then I tried with a simple for loop, not a parfor loop on both Linux and Windows. On Linux, the error persists but on Windows the for loop version works.
Thanks in advance.

  10 Comments

I cannot test it without the mex function because I need that for the later codes to work. And even later, the loop without the mex function crashes at different iteration numbers. And different parts of the code on Linux and on Windows.
OCDER
on 17 Nov 2017
This does sound like one of the worst case scenario for debugging codes. You might have to contact the authors of the 3rd party MEX codes to find the memory allocation bug. Without looking at all the codes, it'll be hard to pinpoint the issue. This might help with debugging strategies:
Thank you. I may use valgrind/callgrid to profile the mex file. If you write an answer I will accept it. Although my problem persists (it's too vague to be solved immediately), you gave me good advices.

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