!!!!!!!!!!!!!!!!!!!!!!!!!!! Program 2.14 !!!!!!!!!!!!!!!!!!!!!!!!!!!!
!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! !
! Please Note: !
! !
! (1) This computer program is written by Tao Pang in conjunction with !
! his book, "An Introduction to Computational Physics," published !
! by Cambridge University Press in 1997. !
! !
! (2) No warranties, express or implied, are made for this program. !
! !
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!
MODULE CSEED
INTEGER :: ISEED
END MODULE CSEED
!
SUBROUTINE PERCOLATION (L,N,M,P)
!
! Subroutine to create an N*M percolation network.
! Copyright (c) Tao Pang 1997.
!
INTEGER, INTENT (IN) :: N,M
REAL, INTENT (IN) :: P
REAL:: R,RANF
LOGICAL, INTENT (OUT), DIMENSION (N,M) :: L
!
DO I = 1, N
DO J = 1, M
R = RANF()
IF(R.LT.P) THEN
L(I,J) = .TRUE.
ELSE
L(I,J) = .FALSE.
END IF
END DO
END DO
END SUBROUTINE PERCOLATION
!
FUNCTION RANF() RESULT (R)
!
! Uniform random number generator x(n+1) = a*x(n) mod c with
! a=7**5 and c = 2**(31)-1. Copyright (c) Tao Pang 1997.
!
USE CSEED
IMPLICIT NONE
INTEGER :: IH,IL,IT,IA,IC,IQ,IR
DATA IA/16807/,IC/2147483647/,IQ/127773/,IR/2836/
REAL :: R
!
IH = ISEED/IQ
IL = MOD(ISEED,IQ)
IT = IA*IL-IR*IH
IF(IT.GT.0) THEN
ISEED = IT
ELSE
ISEED = IC+IT
END IF
R = ISEED/FLOAT(IC)
END FUNCTION RANF