dlaruv.c

/* dlaruv.f -- translated by f2c (version 20061008).
   You must link the resulting object file with libf2c:
	on Microsoft Windows system, link with libf2c.lib;
	on Linux or Unix systems, link with .../path/to/libf2c.a -lm
	or, if you install libf2c.a in a standard place, with -lf2c -lm
	-- in that order, at the end of the command line, as in
		cc *.o -lf2c -lm
	Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,

		http://www.netlib.org/f2c/libf2c.zip
*/

#include "clapack.h"


/* Subroutine */ int dlaruv_(integer *iseed, integer *n, doublereal *x)
{
    /* Initialized data */

    static integer mm[512]	/* was [128][4] */ = { 494,2637,255,2008,1253,
	    3344,4084,1739,3143,3468,688,1657,1238,3166,1292,3422,1270,2016,
	    154,2862,697,1706,491,931,1444,444,3577,3944,2184,1661,3482,657,
	    3023,3618,1267,1828,164,3798,3087,2400,2870,3876,1905,1593,1797,
	    1234,3460,328,2861,1950,617,2070,3331,769,1558,2412,2800,189,287,
	    2045,1227,2838,209,2770,3654,3993,192,2253,3491,2889,2857,2094,
	    1818,688,1407,634,3231,815,3524,1914,516,164,303,2144,3480,119,
	    3357,837,2826,2332,2089,3780,1700,3712,150,2000,3375,1621,3090,
	    3765,1149,3146,33,3082,2741,359,3316,1749,185,2784,2202,2199,1364,
	    1244,2020,3160,2785,2772,1217,1822,1245,2252,3904,2774,997,2573,
	    1148,545,322,789,1440,752,2859,123,1848,643,2405,2638,2344,46,
	    3814,913,3649,339,3808,822,2832,3078,3633,2970,637,2249,2081,4019,
	    1478,242,481,2075,4058,622,3376,812,234,641,4005,1122,3135,2640,
	    2302,40,1832,2247,2034,2637,1287,1691,496,1597,2394,2584,1843,336,
	    1472,2407,433,2096,1761,2810,566,442,41,1238,1086,603,840,3168,
	    1499,1084,3438,2408,1589,2391,288,26,512,1456,171,1677,2657,2270,
	    2587,2961,1970,1817,676,1410,3723,2803,3185,184,663,499,3784,1631,
	    1925,3912,1398,1349,1441,2224,2411,1907,3192,2786,382,37,759,2948,
	    1862,3802,2423,2051,2295,1332,1832,2405,3638,3661,327,3660,716,
	    1842,3987,1368,1848,2366,2508,3754,1766,3572,2893,307,1297,3966,
	    758,2598,3406,2922,1038,2934,2091,2451,1580,1958,2055,1507,1078,
	    3273,17,854,2916,3971,2889,3831,2621,1541,893,736,3992,787,2125,
	    2364,2460,257,1574,3912,1216,3248,3401,2124,2762,149,2245,166,466,
	    4018,1399,190,2879,153,2320,18,712,2159,2318,2091,3443,1510,449,
	    1956,2201,3137,3399,1321,2271,3667,2703,629,2365,2431,1113,3922,
	    2554,184,2099,3228,4012,1921,3452,3901,572,3309,3171,817,3039,
	    1696,1256,3715,2077,3019,1497,1101,717,51,981,1978,1813,3881,76,
	    3846,3694,1682,124,1660,3997,479,1141,886,3514,1301,3604,1888,
	    1836,1990,2058,692,1194,20,3285,2046,2107,3508,3525,3801,2549,
	    1145,2253,305,3301,1065,3133,2913,3285,1241,1197,3729,2501,1673,
	    541,2753,949,2361,1165,4081,2725,3305,3069,3617,3733,409,2157,
	    1361,3973,1865,2525,1409,3445,3577,77,3761,2149,1449,3005,225,85,
	    3673,3117,3089,1349,2057,413,65,1845,697,3085,3441,1573,3689,2941,
	    929,533,2841,4077,721,2821,2249,2397,2817,245,1913,1997,3121,997,
	    1833,2877,1633,981,2009,941,2449,197,2441,285,1473,2741,3129,909,
	    2801,421,4073,2813,2337,1429,1177,1901,81,1669,2633,2269,129,1141,
	    249,3917,2481,3941,2217,2749,3041,1877,345,2861,1809,3141,2825,
	    157,2881,3637,1465,2829,2161,3365,361,2685,3745,2325,3609,3821,
	    3537,517,3017,2141,1537 };

    /* System generated locals */
    integer i__1;

    /* Local variables */
    integer i__, i1, i2, i3, i4, it1, it2, it3, it4;


/*  -- LAPACK auxiliary routine (version 3.2) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

/*     .. Scalar Arguments .. */
/*     .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  DLARUV returns a vector of n random real numbers from a uniform (0,1) */
/*  distribution (n <= 128). */

/*  This is an auxiliary routine called by DLARNV and ZLARNV. */

/*  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. */

/*  N       (input) INTEGER */
/*          The number of random numbers to be generated. N <= 128. */

/*  X       (output) DOUBLE PRECISION array, dimension (N) */
/*          The generated random numbers. */

/*  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. */

/*  ===================================================================== */

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. Local Arrays .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Data statements .. */
    /* Parameter adjustments */
    --iseed;
    --x;

    /* Function Body */
/*     .. */
/*     .. Executable Statements .. */

    i1 = iseed[1];
    i2 = iseed[2];
    i3 = iseed[3];
    i4 = iseed[4];

    i__1 = min(*n,128);
    for (i__ = 1; i__ <= i__1; ++i__) {

L20:

/*        Multiply the seed by i-th power of the multiplier modulo 2**48 */

	it4 = i4 * mm[i__ + 383];
	it3 = it4 / 4096;
	it4 -= it3 << 12;
	it3 = it3 + i3 * mm[i__ + 383] + i4 * mm[i__ + 255];
	it2 = it3 / 4096;
	it3 -= it2 << 12;
	it2 = it2 + i2 * mm[i__ + 383] + i3 * mm[i__ + 255] + i4 * mm[i__ + 
		127];
	it1 = it2 / 4096;
	it2 -= it1 << 12;
	it1 = it1 + i1 * mm[i__ + 383] + i2 * mm[i__ + 255] + i3 * mm[i__ + 
		127] + i4 * mm[i__ - 1];
	it1 %= 4096;

/*        Convert 48-bit integer to a real number in the interval (0,1) */

	x[i__] = ((doublereal) it1 + ((doublereal) it2 + ((doublereal) it3 + (
		doublereal) it4 * 2.44140625e-4) * 2.44140625e-4) * 
		2.44140625e-4) * 2.44140625e-4;

	if (x[i__] == 1.) {
/*           If a real number has n bits of precision, and the first */
/*           n bits of the 48-bit integer above happen to be all 1 (which */
/*           will occur about once every 2**n calls), then X( I ) will */
/*           be rounded to exactly 1.0. */
/*           Since X( I ) is not supposed to return exactly 0.0 or 1.0, */
/*           the statistically correct thing to do in this situation is */
/*           simply to iterate again. */
/*           N.B. the case X( I ) = 0.0 should not be possible. */
	    i1 += 2;
	    i2 += 2;
	    i3 += 2;
	    i4 += 2;
	    goto L20;
	}

/* L10: */
    }

/*     Return final value of seed */

    iseed[1] = it1;
    iseed[2] = it2;
    iseed[3] = it3;
    iseed[4] = it4;
    return 0;

/*     End of DLARUV */

} /* dlaruv_ */