C********************************************************************** C SUBROUTINE SRANDN (N,DX,SEED) C C Purpose: C Fills the vector DX with random numbers between 0 and 1. If the C SEED is given, it should be odd and positive. The generator is a C fairly unsophisticated one, from Pearson's "Numerical methods in C engineering and science" book. C C Parameters: C N = the dimension of the vector (input). C DX = the vector to fill with random numbers (output). C SEED = the seed for the generator (input). C C Noel M. Nachtigal C April 23, 1993 C C********************************************************************** C INTRINSIC FLOAT, IABS, MOD C INTEGER N, SEED REAL DX(N) C C Local variables. C INTEGER I, J C C Local variables that are saved from one call to the next. C REAL DMAX INTEGER IM, IMAX, IS SAVE DMAX, IM, IMAX, IS DATA IM/0/ C C Initialize the generator data. C IF (IM.EQ.0) THEN J = 0 IM = 1 DO 10 I = 1, 31 J = J + 1 IF (IM*2.LE.IM) GO TO 20 IM = IM * 2 10 CONTINUE 20 IMAX = (IM-1) * 2 + 1 DMAX = FLOAT(IMAX) DO 30 I = 1, MOD(J,3) J = J - 1 IM = IM / 2 30 CONTINUE IM = IM + 5 IS = IABS(MOD(IM*30107,IMAX)) END IF C C Check whether we have a new seed. C IF (SEED.GT.0) IS = (SEED / 2) * 2 + 1 C C Here goes the rest. C DO 40 I = 1, N DX(I) = FLOAT(IS) / DMAX IS = IABS(MOD(IM*IS,IMAX)) 40 CONTINUE C RETURN END C C**********************************************************************