Re: cellfun and parcellfun

[David Bateman]

Robert Patterson wrote:
> On Fri, 2010-06-11 at 23:28 +0200, David Bateman wrote:
>   
> > It should be 
> > relatively easy to do this except for the care needed with the fact that 
> > the randlib generators all use the same state and the mersenne twister 
> > based generators have separate states and so rand("state", "reset") 
> > should change only the uniform generators state, but rand("seed", 
> > "reset") should change all of them.
> >
> >     
>
> I think I am doing something pretty stupid in trying to reset my RNGs:
>
> octave:187> rand("state", 123); rande()
> ans =  0.042798
> octave:188> rand("state", 123); rande()
> ans =  0.49064
> octave:189> rand("state", 123); rande()
> ans =  4.2087
>
> I was expecting to get the same value each time.  Is the hash used to
> initialise the Mersenne Twister non-deterministic?
>
> Thanks
>
> Robert
>
>
>   
The older randlib generators have the same base generator so the above 
will work if you replace "state" by "seed". However the cost of that 
will be speed and a short length of the pseudo random sequence...

The Mersenne Twister hash is deterministic but you have to initialize 
each generator separately

octave:1> rande("state",123); rande()
ans =  0.27640
octave:2> rande("state",123); rande()
ans =  0.27640
octave:3> rande("state",123); rande()
ans =  0.27640

D.