No true random for standalone (files only) in AppDesigner?

Hi,

i wrote an App with the AppDesigner which includes Monte Carlo Simulatoin with multiple random generators.

When I execute the app multiple time directly within the app designer everything is as is should be. The distributions are similiar but every single index of the array has a different (random) value.

For distribution I decided that colleagues shall download the runtime and they get a standalone .exe file. But here I happens that when you execute the app 2 times with the very same inputs you get for every index of the array the same value.

Question 1: Is that a bug?

Question 2: Is there an easy workaround, in which I can keep the standalone .exe distribution.

I already tried to tic toc some times in functions to get a random-like input and wrote dem to a struct (app.a.b=toc), but the random still led to always the same result.

Thanks

Answer 1

[the cyclist]

Disclaimer: I've never used AppDesigner, or distributed standalone MATLAB exe files.

Sounds like it is starting from the default initial seed each time. Can you put

rng shuffle

in the code, to ensure a different random number seed?

[Karsten Wilde]

Thats an easy solution.

It works. Thanks.

[the cyclist]

As @Steven Lord mentions in his answer, but bears repeating because it is important, it is recommended to insert that seed-setting line into your code just once (before the first call to any function that uses the random number generator), and not before each call.

Answer 2

[Steven Lord]

Question 1: Is that a bug?

No. See this documentation page for an explanation. While that talks about MATLAB startup, it also applies to starting the MATLAB runtime.

Question 2: Is there an easy workaround, in which I can keep the standalone .exe distribution.

See that documentation page I linked above. But note that you shouldn't reseed the generator every time you draw a new random number as per the Note on this documentation page.