REAL FUNCTION RAND()
C
C     THIS FUNCTION RETURNS A PSEUDO-RANDOM NUMBER FOR EACH INVOCATION.
C     IT IS A FORTRAN 77 ADAPTATION OF THE "INTEGER VERSION 2" MINIMAL
C     STANDARD NUMBER GENERATOR WHOSE PASCAL CODE APPEARS IN THE
C     ARTICLE:
C
C         PARK, STEVEN K. AND MILLER, KEITH W., "RANDOM NUMBER
C         GENERATORS: GOOD ONES ARE HARD TO FIND", COMMUNICATIONS OF
C         THE ACM, OCTOBER, 1988.
C
C     FORTRAN 77 IMPLEMENTATION BY DICK VALENT AND FRED CLARE.
C
      INTEGER MPLIER, MODLUS, MOBYMP, MOMDMP
      PARAMETER (MPLIER=16807, MODLUS=2147483647, MOBYMP=127773,
     &           MOMDMP=2836)
      COMMON  /SEED/ JSEED, IFRST
      INTEGER HVLUE, LVLUE, TESTV, NEXTN
      SAVE    NEXTN

      IF (IFRST .EQ. 0) THEN
        NEXTN = JSEED
        IFRST = 1
      END IF

      HVLUE = NEXTN / MOBYMP
      LVLUE = MOD(NEXTN, MOBYMP)
      TESTV = MPLIER * LVLUE - MOMDMP * HVLUE

      IF (TESTV .GT. 0) THEN
        NEXTN = TESTV
      ELSE
        NEXTN = TESTV + MODLUS
      END IF

      RAND = REAL(NEXTN) / REAL(MODLUS)
      END
C     ******************************************************************
      SUBROUTINE SRAND(ISEED)
C
C     THIS SUBROUTINE SETS THE INTEGER SEED TO BE USED WITH THE
C     COMPANION RAND FUNCTION TO THE VALUE OF ISEED. A FLAG IS SET TO
C     INDICATE THAT THE SEQUENCE OF PSEUDO-RANDOM NUMBERS FOR THE
C     SPECIFIED SEED SHOULD START FROM THE BEGINNING.
C
      INTEGER ISEED
      COMMON /SEED/ JSEED, IFRST
      JSEED = ISEED
      IFRST = 0
      END