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Annotation of 43BSDReno/lib/libm/common_source/fmod.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1989 The Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms are permitted
        !             6:  * provided that: (1) source distributions retain this entire copyright
        !             7:  * notice and comment, and (2) distributions including binaries display
        !             8:  * the following acknowledgement:  ``This product includes software
        !             9:  * developed by the University of California, Berkeley and its contributors''
        !            10:  * in the documentation or other materials provided with the distribution
        !            11:  * and in all advertising materials mentioning features or use of this
        !            12:  * software. Neither the name of the University nor the names of its
        !            13:  * contributors may be used to endorse or promote products derived
        !            14:  * from this software without specific prior written permission.
        !            15:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            16:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            17:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            18:  */
        !            19: 
        !            20: #ifndef lint
        !            21: static char sccsid[] = "@(#)fmod.c     5.2 (Berkeley) 6/1/90";
        !            22: #endif /* not lint */
        !            23: 
        !            24: /* fmod.c
        !            25:  *
        !            26:  * SYNOPSIS
        !            27:  *
        !            28:  *    #include <math.h>
        !            29:  *    double fmod(double x, double y)
        !            30:  *
        !            31:  * DESCRIPTION
        !            32:  *
        !            33:  *    The fmod function computes the floating-point remainder of x/y.
        !            34:  *
        !            35:  * RETURNS
        !            36:  *
        !            37:  *    The fmod function returns the value x-i*y, for some integer i
        !            38:  * such that, if y is nonzero, the result has the same sign as x and
        !            39:  * magnitude less than the magnitude of y.
        !            40:  *
        !            41:  * On a VAX or CCI,
        !            42:  *
        !            43:  *    fmod(x,0) traps/faults on floating-point divided-by-zero.
        !            44:  *
        !            45:  * On IEEE-754 conforming machines with "isnan()" primitive,
        !            46:  *
        !            47:  *    fmod(x,0), fmod(INF,y) are invalid operations and NaN is returned.
        !            48:  *
        !            49:  */
        !            50: #if !defined(vax) && !defined(tahoe)
        !            51: extern int isnan(),finite();
        !            52: #endif /* !defined(vax) && !defined(tahoe) */
        !            53: extern double frexp(),ldexp(),fabs();
        !            54: 
        !            55: #ifdef TEST_FMOD
        !            56: static double
        !            57: _fmod(x,y)
        !            58: #else  /* TEST_FMOD */
        !            59: double
        !            60: fmod(x,y)
        !            61: #endif /* TEST_FMOD */
        !            62: double x,y;
        !            63: {
        !            64:        int ir,iy;
        !            65:        double r,w;
        !            66: 
        !            67:        if (y == (double)0
        !            68: #if !defined(vax) && !defined(tahoe)   /* per "fmod" manual entry, SunOS 4.0 */
        !            69:                || isnan(y) || !finite(x)
        !            70: #endif /* !defined(vax) && !defined(tahoe) */
        !            71:            )
        !            72:            return (x*y)/(x*y);
        !            73: 
        !            74:        r = fabs(x);
        !            75:        y = fabs(y);
        !            76:        (void)frexp(y,&iy);
        !            77:        while (r >= y) {
        !            78:                (void)frexp(r,&ir);
        !            79:                w = ldexp(y,ir-iy);
        !            80:                r -= w <= r ? w : w*(double)0.5;
        !            81:        }
        !            82:        return x >= (double)0 ? r : -r;
        !            83: }
        !            84: 
        !            85: #ifdef TEST_FMOD
        !            86: extern long random();
        !            87: extern double fmod();
        !            88: 
        !            89: #define        NTEST   10000
        !            90: #define        NCASES  3
        !            91: 
        !            92: static int nfail = 0;
        !            93: 
        !            94: static void
        !            95: doit(x,y)
        !            96: double x,y;
        !            97: {
        !            98:        double ro = fmod(x,y),rn = _fmod(x,y);
        !            99:        if (ro != rn) {
        !           100:                (void)printf(" x    = 0x%08.8x %08.8x (%24.16e)\n",x,x);
        !           101:                (void)printf(" y    = 0x%08.8x %08.8x (%24.16e)\n",y,y);
        !           102:                (void)printf(" fmod = 0x%08.8x %08.8x (%24.16e)\n",ro,ro);
        !           103:                (void)printf("_fmod = 0x%08.8x %08.8x (%24.16e)\n",rn,rn);
        !           104:                (void)printf("\n");
        !           105:        }
        !           106: }
        !           107: 
        !           108: main()
        !           109: {
        !           110:        register int i,cases;
        !           111:        double x,y;
        !           112: 
        !           113:        srandom(12345);
        !           114:        for (i = 0; i < NTEST; i++) {
        !           115:                x = (double)random();
        !           116:                y = (double)random();
        !           117:                for (cases = 0; cases < NCASES; cases++) {
        !           118:                        switch (cases) {
        !           119:                        case 0:
        !           120:                                break;
        !           121:                        case 1:
        !           122:                                y = (double)1/y; break;
        !           123:                        case 2:
        !           124:                                x = (double)1/x; break;
        !           125:                        default:
        !           126:                                abort(); break;
        !           127:                        }
        !           128:                        doit(x,y);
        !           129:                        doit(x,-y);
        !           130:                        doit(-x,y);
        !           131:                        doit(-x,-y);
        !           132:                }
        !           133:        }
        !           134:        if (nfail)
        !           135:                (void)printf("Number of failures: %d (out of a total of %d)\n",
        !           136:                        nfail,NTEST*NCASES*4);
        !           137:        else
        !           138:                (void)printf("No discrepancies were found\n");
        !           139:        exit(0);
        !           140: }
        !           141: #endif /* TEST_FMOD */

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