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[Octave-bug-tracker] [bug #30399] DLD can change rand distribution in oc
From: |
julien javaloyes |
Subject: |
[Octave-bug-tracker] [bug #30399] DLD can change rand distribution in octave interpreter |
Date: |
Fri, 09 Jul 2010 13:37:31 +0000 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.6) Gecko/20100628 Ubuntu/10.04 (lucid) Firefox/3.6.6 |
URL:
<http://savannah.gnu.org/bugs/?30399>
Summary: DLD can change rand distribution in octave
interpreter
Project: GNU Octave
Submitted by: javaloye
Submitted on: Fri 09 Jul 2010 01:37:30 PM GMT
Category: Libraries
Severity: 3 - Normal
Item Group: Incorrect Result
Status: None
Assigned to: None
Originator Name: julien
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Release: 3.2.3
Operating System: GNU/Linux
_______________________________________________________
Details:
in octave interpreter "rand" gives uniform random numbers while randn gives
gaussian random numbers.
Indeed, calling
--rand ("state", [1:625]); rand
gives uniform numbers.
However, after calling within the interpreter a dld function that changes the
mode of the random number generator like below
--dummyfunc
subsequent calls to
--rand ("state", [1:625]); rand
produces gaussian and not anymore uniform random numbers.
--This bug does not depend on the seed of the generator, i.e. replace [1:625]
by anything integer.
Fixing is easy as one simply need to reset the mode of the generator before
exiting the dld function.
However, I think that a dld function should not be able to "swap" the rand
and the randn functions in octave interpreter.
dld function compiled with mkoctfile
#include <octave/oct.h>
#include <octave/oct-rand.h>
DEFUN_DLD (dummyfunc,args,nargout,"")
{
octave_rand::distribution("normal"); // put octave random generator to
gaussian mode
// do something
//octave_rand::distribution("uniform"); // put the generator back to uniform
mode for correct behavior
return octave_value_list();
//----------------------------------------------------------//
}
_______________________________________________________
Reply to this item at:
<http://savannah.gnu.org/bugs/?30399>
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