Re: [OctDev] randn() broken

[David B. <Dav...@mo...>]

I can't regenerate this problem with octave-forge CVS or with 2004.09.09.
I used the commands

octave:1> hist(randn(1,1e6),-3.75:0.5:3.75)
octave:2> var(randn(1,1e6))
ans =3D 1.0001
octave:3> mean(randn(1,1e6))
ans =3D  -4.9951e-04

Which clearly showed a normal distribution and the correct mean and varianc=
e.
Maybe your problem is to do with the seeding of the generator, however it
this case you would also have a poor return from rand from octave-forge,
since they both use the same basic generator... Try running

randn("seed", 12345)

before doing your test and seed if it helps. It might also be a build
issue, so can you try with the "-DALLBITS" flag or without it and
see if it makes a difference if 32 or 64 bit ints are used.

It would be better if you can properly diagnose your problem, as the
randn generator in 2.1.57 is much shorter period than that from
octave-forge and is much slower, but equally is the report of the form
you sent does no one any good, and if it is a true bug others should
profit from your problems/solutions.

Regards
David

According to Justus Piater <Jus...@UL...> (on 11/08/04):
> Hi,
>=20
> randn() from octave-forge-2004.09.09 (CVS version 1.11) appears to be
> broken. The generated numbers are clearly not normally distributed:
> Numbers near zero (the most likely numbers) are extremely rare, and
> stretches of generated numbers appear to be sampled from different
> distributions that vary from some 10s to some 1000s of numbers in
> length.
>=20
> See for yourselves by issuing
>=20
>         plot(1:10000, randn(1, 10000), ".");
>=20
> I have not tested later versions from CVS, but the CVS logs do not
> suggest that this has been fixed. For my purposes, I'm reverting back
> to the randn() from octave-2.1.57 whose output looks ok.
>=20
> Justus
>=20
> --=20
> Justus H. Piater, Ph.D.         http://www.montefiore.ulg.ac.be/~piater/
> Institut Montefiore, B28        Phone: +32-4-366-2279
> Universit=E9 de Li=E8ge, Belgium    Fax:   +32-4-366-2620
>=20
>=20
>=20
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David Bateman                                Dav...@mo...
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