[OctDev] Repeating same sequence of rand/randn between octave/matlab

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

I was recently required to reproduce the same sequence of random numbers 
in octave and matlab to demonstrate bit accurate simulation between two 
versions of the same simulator (one under octave and the other under 
matlab). My means of doing this was to replace the matlab rand/randn 
functions with ones based on the code from octave-forge. I attach the 
mexFunction to allow this to this message in case others find themselves 
in the same position.

There are a couple of points to note.

1) You must obtain randmtzig.c from octave-forge
2) The compile flag will be dependent on the machine but to compile the 
code for matlab under x86 linux I used
     "mex -O -DEXPORT -DALLBITS -DUSE_X86_32=1 rand.c"
3) The mexFunction should either be copied or symbolically linked to 
randn mexFunction (under linux randn.mexglx)
4) The octave-forge versions of rand.oct and rand.oct must NOT be a 
symbolic link from one to the other. This ensures that
    the two random function use separate instantiations of the Mersenne 
Twister. This is not the case for a standard install
   of octave-forge and so again rand.oct and randn.oct should be copied.
5) Both rand and randn must be seeded separately at the start of the 
simulation since they use seperate instantiations of
    the Mersenne Twister

Enjoy
David

-- 
David Bateman                                Dav...@mo...
Motorola Labs - Paris                        +33 1 69 35 48 04 (Ph) 
Parc Les Algorithmes, Commune de St Aubin    +33 1 69 35 77 01 (Fax) 
91193 Gif-Sur-Yvette FRANCE

The information contained in this communication has been classified as: 

[x] General Business Information 
[ ] Motorola Internal Use Only 
[ ] Motorola Confidential Proprietary