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/GNU Fortran 7

9.153 IRAND — Integer pseudo-random number

Description:

IRAND(FLAG) returns a pseudo-random number from a uniform distribution between 0 and a system-dependent limit (which is in most cases 2147483647). 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 = IRAND(I)

Arguments:
I Shall be a scalar INTEGER of kind 4.
Return value:

The return value is of INTEGER(kind=4) type.

Example:
program test_irand
  integer,parameter :: seed = 86456
  
  call srand(seed)
  print *, irand(), irand(), irand(), irand()
  print *, irand(seed), irand(), irand(), irand()
end program test_irand

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https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gfortran/IRAND.html