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Top Forums Programming Random numbers in parent/child? Post 302356746 by jim mcnamara on Sunday 27th of September 2009 10:00:44 AM
Old 09-27-2009
Because the child process has the exact same seed value as the parent.

Move the srand statment down inside the if(pid ... ) blocks.
Use two different prime numbers say: 13 and 8191. Then you will get different values.
Time as a ssed may not necessarily work - you can try calling seedit() down inside the if blocks if you want to test how well it works.
 

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rand(3UCB)					     SunOS/BSD Compatibility Library Functions						rand(3UCB)

NAME
rand, srand - simple random number generator SYNOPSIS
/usr/ucb/cc[ flag ... ] file ... int rand() int srand( seed); unsigned seed; DESCRIPTION
rand() uses a multiplicative congruential random number generator with period 2**32 to return successive pseudo-random numbers in the range from 0 to "2**31 -1." srand() can be called at any time to reset the random-number generator to a random starting point. The generator is initially seeded with a value of 1. SEE ALSO
drand48(3C), rand(3C), random(3C) NOTES
Use of these interfaces should be restricted to only applications written on BSD platforms. Use of these interfaces with any of the system libraries or in multi-thread applications is unsupported. The spectral properties of rand() leave a great deal to be desired. drand48(3C) and random(3C) provide much better, though more elaborate, random-number generators. The low bits of the numbers generated are not very random; use the middle bits. In particular the lowest bit alternates between 0 and 1. SunOS 5.10 12 Feb 1993 rand(3UCB)
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