Error with MATLAB batch function

Question

I'm trying to use batch to simply run 5 parallel instances of a script. As a test I tried this:

for ii = 1:5
  jj{ii} = batch('magic(5000)');
end
wait(jj{5});

This appears to work, however I get a big nasty warning at each of the 5 times through. It's on a non-networked machine, but the headline is:

"Warning: Objects of class 'parallel.job.CJSIndependentJob' cannot be saved to MAT files."

This error is actually repeated 4 times per loop iteration.

Any ideas what the problem is here? I'm not intending to save anything to disk.

have you checked out this question/answer, its similar to yours: stackoverflow.com/questions/28381574/… — jack
– jack, Commented Sep 15, 2015 at 19:57

Edric · Accepted Answer · 2015-09-16 07:55:44Z

1

The warning appears because by default when the batch command is used to invoke a script (or a string, as here), it captures the entire workspace and sends it to the workers so that they can use it for their computations. This lets you do stuff like this:

x = 100;
j = batch('size(x)')

and have it work.

In your case, you have two options - you can specify the 'Workspace' option to batch, like so:

j{ii} = batch('magic(1000)', 'Workspace', struct());

or, you could use a function:

j{ii} = batch(@magic, 1, {1000}); % 1 is number of outputs requested

answered Sep 16, 2015 at 7:55

Edric

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