#include "blaswrap.h" /* -- translated by f2c (version 19990503). You must link the resulting object file with the libraries: -lf2c -lm (in that order) */ #include "f2c.h" doublereal dlaran_(integer *iseed) { /* System generated locals */ doublereal ret_val; /* Local variables */ static integer it1, it2, it3, it4; /* -- LAPACK auxiliary routine (version 3.0) -- Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., Courant Institute, Argonne National Lab, and Rice University February 29, 1992 Purpose ======= DLARAN returns a random real number from a uniform (0,1) distribution. Arguments ========= ISEED (input/output) INTEGER array, dimension (4) On entry, the seed of the random number generator; the array elements must be between 0 and 4095, and ISEED(4) must be odd. On exit, the seed is updated. Further Details =============== This routine uses a multiplicative congruential method with modulus 2**48 and multiplier 33952834046453 (see G.S.Fishman, 'Multiplicative congruential random number generators with modulus 2**b: an exhaustive analysis for b = 32 and a partial analysis for b = 48', Math. Comp. 189, pp 331-344, 1990). 48-bit integers are stored in 4 integer array elements with 12 bits per element. Hence the routine is portable across machines with integers of 32 bits or more. ===================================================================== multiply the seed by the multiplier modulo 2**48 Parameter adjustments */ --iseed; /* Function Body */ it4 = iseed[4] * 2549; it3 = it4 / 4096; it4 -= it3 << 12; it3 = it3 + iseed[3] * 2549 + iseed[4] * 2508; it2 = it3 / 4096; it3 -= it2 << 12; it2 = it2 + iseed[2] * 2549 + iseed[3] * 2508 + iseed[4] * 322; it1 = it2 / 4096; it2 -= it1 << 12; it1 = it1 + iseed[1] * 2549 + iseed[2] * 2508 + iseed[3] * 322 + iseed[4] * 494; it1 %= 4096; /* return updated seed */ iseed[1] = it1; iseed[2] = it2; iseed[3] = it3; iseed[4] = it4; /* convert 48-bit integer to a real number in the interval (0,1) */ ret_val = ((doublereal) it1 + ((doublereal) it2 + ((doublereal) it3 + ( doublereal) it4 * 2.44140625e-4) * 2.44140625e-4) * 2.44140625e-4) * 2.44140625e-4; return ret_val; /* End of DLARAN */ } /* dlaran_ */