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[Octave-bug-tracker] [bug #54342] rand() produces different results on o


From: Dan Sebald
Subject: [Octave-bug-tracker] [bug #54342] rand() produces different results on octave 4.4.0 compared to earlier versions
Date: Sun, 22 Jul 2018 15:51:50 -0400 (EDT)
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:55.0) Gecko/20100101 Firefox/55.0

Follow-up Comment #17, bug #54342 (project octave):

I'm not sure it is worthwhile trying to aim for compatibility with Matlab v5,
as the random number generators for that version apparently aren't
statistically in line with randomness and Mathworks suggests not using that
anymore.  So maybe it is best to just make Octave 4.4.1 rand() "seed" and
"state" consistent with Octave 4.2.2 rand() and consider it deprecated at that
point.  (Add a note to rand() documentation that "seed"/"state" will be
deprecated and things will be considerably different in the future, not only
in syntax but also default seed.)  Hopefully there aren't too many users
who've gotten used to the Octave 4.4.0 'state' behavior for rand().

Then in future versions, look towards consistency with all the other numerical
programs using the twister code (i.e., the link in Comment #15).  *Maybe* then
add a "seedlegacy" option to whatever routine seeds the future generator that
will reset the r.n.g. to the seed used in Octave 4.4.1/4.2.2.  That way,
there's a good chance that users can run their legacy code in the future and
be able to repeat results of old.

Moving forward will be a bit confusing because of underlying issues of how the
generator is used, but this way there'd be a straightforward solution in the
short term.

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