hijing/src/rlu.f

0001
0002 C*********************************************************************
0003
0004       FUNCTION RLU(IDUM)
0005
0006 C...Purpose: to generate random numbers uniformly distributed between
0007 C...0 and 1, excluding the endpoints.
0008       COMMON/LUDATR/MRLU(6),RRLU(100)
0009       SAVE /LUDATR/
0010       EQUIVALENCE (MRLU1,MRLU(1)),(MRLU2,MRLU(2)),(MRLU3,MRLU(3)),
0011      &(MRLU4,MRLU(4)),(MRLU5,MRLU(5)),(MRLU6,MRLU(6)),
0012      &(RRLU98,RRLU(98)),(RRLU99,RRLU(99)),(RRLU00,RRLU(100))
0013
0014 C...Initialize generation from given seed.
0015       IF(MRLU2.EQ.0) THEN
0016         IJ=MOD(MRLU1/30082,31329)
0017         KL=MOD(MRLU1,30082)
0018         I=MOD(IJ/177,177)+2
0019         J=MOD(IJ,177)+2
0020         K=MOD(KL/169,178)+1
0021         L=MOD(KL,169)
0022         DO 110 II=1,97
0023         S=0.
0024         T=0.5
0025         DO 100 JJ=1,24
0026         M=MOD(MOD(I*J,179)*K,179)
0027         I=J
0028         J=K
0029         K=M
0030         L=MOD(53*L+1,169)
0031         IF(MOD(L*M,64).GE.32) S=S+T
0032   100   T=0.5*T
0033   110   RRLU(II)=S
0034         TWOM24=1.
0035         DO 120 I24=1,24
0036   120   TWOM24=0.5*TWOM24
0037         RRLU98=362436.*TWOM24
0038         RRLU99=7654321.*TWOM24
0039         RRLU00=16777213.*TWOM24
0040         MRLU2=1
0041         MRLU3=0
0042         MRLU4=97
0043         MRLU5=33
0044       ENDIF
0045
0046 C...Generate next random number.
0047   130 RUNI=RRLU(MRLU4)-RRLU(MRLU5)
0048       IF(RUNI.LT.0.) RUNI=RUNI+1.
0049       RRLU(MRLU4)=RUNI
0050       MRLU4=MRLU4-1
0051       IF(MRLU4.EQ.0) MRLU4=97
0052       MRLU5=MRLU5-1
0053       IF(MRLU5.EQ.0) MRLU5=97
0054       RRLU98=RRLU98-RRLU99
0055       IF(RRLU98.LT.0.) RRLU98=RRLU98+RRLU00
0056       RUNI=RUNI-RRLU98
0057       IF(RUNI.LT.0.) RUNI=RUNI+1.
0058       IF(RUNI.LE.0.OR.RUNI.GE.1.) GOTO 130
0059
0060 C...Update counters. Random number to output.
0061       MRLU3=MRLU3+1
0062       IF(MRLU3.EQ.1000000000) THEN
0063         MRLU2=MRLU2+1
0064         MRLU3=0
0065       ENDIF
0066       RLU=RUNI
0067
0068       RETURN
0069       END