Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference

ID 767251
Date 3/22/2024
Public

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Document Table of Contents

DRAND, DRANDM

Portability Functions: Return double-precision random numbers in the range 0.0 to 1.0, not including the end points.

Module

USE IFPORT

result = DRAND (iflag)

result = DRANDM (iflag)

iflag

(Input) INTEGER(4). Controls the way the random number is selected.

Results

The result type is REAL(8). DRAND and DRANDM return random numbers in the range 0.0 to 1.0, not including the end points.

Value of iflag

Selection process

1

The generator is restarted and the first random value is selected.

0

The next random number in the sequence is selected.

Otherwise

The generator is reseeded using iflag, then restarted, and the first random value is selected.

There is no difference between DRAND and DRANDM. Both functions are included to insure portability of existing code that references one or both of them.

The intrinsic subroutines RANDOM_INIT, RANDOM_NUMBER, and RANDOM_SEED provide the same functionality and they are the recommended functions to use when writing programs to generate random numbers.

Example

USE IFPORT
REAL(8) num
INTEGER(4) f
f=1
CALL print_rand
f=0
CALL print_rand
f=22
CALL print_rand
CONTAINS
  SUBROUTINE print_rand
    num = drand(f)
    print *, 'f= ',f,':',num
  END SUBROUTINE
END