Does Matlab initialize random seed at each -batch run?

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Chern Hui Lee
Chern Hui Lee on 12 Oct 2021
Edited: Jan on 12 Oct 2021
I have 2 scripts, let's call it ScriptA.m and ScriptB.m. ScriptB.m is supposed to be the same as ScriptA.m except with improvement on the algorithm for speed. Both scripts make use of a lot of random numbers, but at different places due to the speed improvement of ScriptB.m. I want to make sure that statistically the two scripts produce the similar result, so I run each one of them 5x using matlab -batch 'run xxx.m', and look at the variation from run-to-run and script-to-script. I noticed that the output of each script is exactly identical across the 5x runs, which is a little strange to me. Does this mean Matlab initialize the random seed for each -batch run? Note that I do not use the function rng in my script for seed initialization. Thanks.
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Chern Hui Lee
Chern Hui Lee on 12 Oct 2021
I realized I can just run the following to confirm that it indeed uses the same random seed each time
matlab -batch 'rng'
and I always get the same seed 0. Pardon the stupid question.

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Accepted Answer

Chern Hui Lee
Chern Hui Lee on 12 Oct 2021
matlab -batch 'rng'
shows that it indeed uses random seed 0 every time.

More Answers (1)

Jan
Jan on 12 Oct 2021
Edited: Jan on 12 Oct 2021
Yes, exactly as you observe the random number generator is initialized with the same seed.
Use rng to get different seeds. See:
doc rng
"To create one or more independent streams separate from the global stream, see RandStream and RandStream.create. "

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