RANDU

Intrinsic Subroutine: Computes a pseudorandom number as a single-precision value.

Syntax

CALL RANDU (i1, i2, x)

i1, i2
INTEGER(2) variables or array elements that contain the seed for computing the random number. These values are updated during the computation so that they contain the updated seed.

x
A REAL(4) variable or array element where the computed random number is returned.

Results:

The result is returned in x, which must be of type REAL(4). The result value is a pseudorandom number in the range 0.0 to 1.0. The algorithm for computing the random number value is based on the values for i1 and i2.

If i1=0 and i2=0, the generator base is set as follows:

    x(n + 1 = 2**16 + 3) 

Otherwise, it is set as follows:

    x(n + 1 = (2**16 + 3) * x(n) mod 2**32) 

The generator base x(n + 1) is stored in i1, i2. The result is x(n + 1) scaled to a real value y(n + 1), for 0.0 <= y(n + 1) < 1.

Example

REAL X
INTEGER(2) I, J
...
CALL RANDU (I, J, X)

If I and J are values 4 and 6, X stores the value 5.4932479E-04.