random() and fork()

[Axel]

Hello
I m trying to having X child process from 1 original process to generate
random numbers.

I m using (1+(int) (10.0*rand()/(RAND_MAX+1.0))) from the man page of
rand() /random().

The problem is that all these childs give as result the absolutly same
value.

Why ? Is it possible to have X forked childs giving different random
values ?

Thanks in advance

Axel

[Joona I Palaste]

Axel <ax************************@netcourrier.com> scribbled the following:

Hello
I m trying to having X child process from 1 original process to generate
random numbers. I m using (1+(int) (10.0*rand()/(RAND_MAX+1.0))) from the man page of
rand() /random(). The problem is that all these childs give as result the absolutly same
value. Why ? Is it possible to have X forked childs giving different random
values ?

Without delving into the platform-specific process-spawning stuff, I
think it's most likely that all your children are getting seeded with
the same seed, thus the PRNG (pseudo-random number generator) generates
the same pseudo-random numbers. Look up srand().

--
/-- Joona Palaste (pa*****@cc.helsinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"I am looking for myself. Have you seen me somewhere?"
- Anon

[Joona I Palaste]

Joona I Palaste <pa*****@cc.helsinki.fi> scribbled the following:

Axel <ax************************@netcourrier.com> scribbled the following:

Hello
I m trying to having X child process from 1 original process to generate
random numbers. I m using (1+(int) (10.0*rand()/(RAND_MAX+1.0))) from the man page of
rand() /random(). The problem is that all these childs give as result the absolutly same
value. Why ? Is it possible to have X forked childs giving different random
values ?

Without delving into the platform-specific process-spawning stuff, I
think it's most likely that all your children are getting seeded with
the same seed, thus the PRNG (pseudo-random number generator) generates
the same pseudo-random numbers. Look up srand().

....noting, after I posted this, the rather funny occurrence of writing
"children are getting seeded"... =)

--
/-- Joona Palaste (pa*****@cc.helsinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"And according to Occam's Toothbrush, we only need to optimise the most frequent
instructions."
- Teemu Kerola