9.221 RAND — Real pseudo-random number

Description:

RAND(FLAG) returns a pseudo-random number from a uniform distribution between 0 and 1. If FLAG is 0, the next number in the current sequence is returned; if FLAG is 1, the generator is restarted by CALL SRAND(0); if FLAG has any other value, it is used as a new seed with SRAND.

This intrinsic routine is provided for backwards compatibility with GNU Fortran 77. It implements a simple modulo generator as provided by g77. For new code, one should consider the use of RANDOM_NUMBER as it implements a superior algorithm.

Standard:

GNU extension

Class:

Function

Syntax:

RESULT = RAND(I)

Arguments:

I	Shall be a scalar INTEGER of kind 4.

Return value:

The return value is of REAL type and the default kind.

Example:

program test_rand
  integer,parameter :: seed = 86456
  
  call srand(seed)
  print *, rand(), rand(), rand(), rand()
  print *, rand(seed), rand(), rand(), rand()
end program test_rand

See also:

SRAND, RANDOM_NUMBER