Matlab Crashes When Executing randperm Function

I am running Matlab 2013b.

I have a function that analyzes data. It runs correctly when executed within Jenkins running on Linux. The code takes about an hour to run.

When I run on my Windows PC in a Putty window connected to a Linux box Matlab crashes every time. It crashes when executing the line "var = randperm(N)", where N is a double with a value = 58. I stepped through the code manually and stopped at different points and typed "var = randperm(58)" without any problem. This problem was verified by a second engineer who had run across the same problem weeks before me.

I have no idea how to troubleshoot this problem.

Thanks in advance for any help.

Mike

[Sulaymon Eshkabilov]

Maybe it is worth trying to use round(). It looks like N is computed somewhere inside your code, e.g.

randperm(round(56.00001))

ans = 1x56

19 5 35 18 55 28 22 46 32 42 23 45 49 24 4 37 33 52 16 25 11 2 10 38 31 17 21 34 6 8

[Michael Cappello]

Hi Sulaymon,

I tried your suggestion but the problem remains. Also, I tried directly passing non-integer values of N into randperm to see how randperm would handle it. randperm performs error checking on the input arguments.

Thank you for the suggestion.

[David Goodmanson]

Hi Sulaymon,

I assume that you are checking the value of N when it crashes on that line (using the debugger although rhere are other ways to accomplish it) and not merely typing

var = randperm(58)

at various spots. If N truly equals 58 it's hard to see how this couId occur. You might also try your own version

function a = randperm1(n)
[~,a] = sort(rand(1,n));  % row vector
end 

just to see what happens.

[Michael Cappello]

David,

"I assume that you are checking the value of N when it crashes on that line"?

Yes. The actual code is

idx = randperm(length(X))

where X is an 1xN double array, and N is always <= 6000.

I stopped at the troublesome line in the debugger and checked that the value was an integer. I even tried stopping at that line and typing in the command window

idx = randperm(2)

and Matlab crashed.

I like your idea of creating a different function and calling that - I hadn't thought of that. I wilI try it. I did however try changing the code to

 NX = length(X);
 idx = datasample(X,NX,'replace','false');

and it still crashes.

Thanks for the suggestion. I'll post my results.

[Jeff Miller]

Maybe check to make sure that

idx = 1:length(X);

works fine?

[Walter Roberson]

What shows up for

which -all randperm

[David Goodmanson]

It doesn't look to be involved here, but unless a person is 100% sure that x is a row or column vector, some people tend to stay away from the length(x) command, using size(x,n) instead because there is no question of one's intent. The length command gives the max size of x along any of its dimensions, which has been known to lead to unwanted surprises.

[Michael Cappello]

Jeff, the following works fine

idx = 1:length(X);

Walter,

which -all randperm

yields the following

built-in (/apps/MATLAB/R2013b/toolbox/matlab/randfun/randperm)

/apps/MATLAB/R2013b/toolbox/matlab/randfun/@RandStream/randperm.mexa64 % RandStream method

/apps/MATLAB/R2013b/toolbox/matlab/randfun/@RandStream/randperm.m % RandStream method

David,

I agree with your use of size over length, but, this is code that has been developed over years that I am now making changes to. I always tread lightly when I am the new guy.

Thank you all for your time.

[Torsten]

I don't know if this could be the reason, but I had a similar problem with "octave" under Windows 11.

Switching the default console to the “Windows Console Host” solved the problem:

https://octave.discourse.group/t/workaround-for-weird-behavior-of-command-window-widget-in-windows/4981/1

But since you work under MATLAB 2013, you might have to have a much lower Windows version installed.