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Diffstat (limited to 'sysdeps/generic/log1p.c')
| -rw-r--r-- | sysdeps/generic/log1p.c | 170 |
1 files changed, 0 insertions, 170 deletions
diff --git a/sysdeps/generic/log1p.c b/sysdeps/generic/log1p.c deleted file mode 100644 index cbf9fcd895..0000000000 --- a/sysdeps/generic/log1p.c +++ /dev/null @@ -1,170 +0,0 @@ -/* - * Copyright (c) 1985, 1993 - * The Regents of the University of California. All rights reserved. - * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions - * are met: - * 1. Redistributions of source code must retain the above copyright - * notice, this list of conditions and the following disclaimer. - * 2. Redistributions in binary form must reproduce the above copyright - * notice, this list of conditions and the following disclaimer in the - * documentation and/or other materials provided with the distribution. - * 3. All advertising materials mentioning features or use of this software - * must display the following acknowledgement: - * This product includes software developed by the University of - * California, Berkeley and its contributors. - * 4. Neither the name of the University nor the names of its contributors - * may be used to endorse or promote products derived from this software - * without specific prior written permission. - * - * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND - * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE - * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE - * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE - * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL - * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS - * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) - * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT - * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY - * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF - * SUCH DAMAGE. - */ - -#ifndef lint -static char sccsid[] = "@(#)log1p.c 8.1 (Berkeley) 6/4/93"; -#endif /* not lint */ - -/* LOG1P(x) - * RETURN THE LOGARITHM OF 1+x - * DOUBLE PRECISION (VAX D FORMAT 56 bits, IEEE DOUBLE 53 BITS) - * CODED IN C BY K.C. NG, 1/19/85; - * REVISED BY K.C. NG on 2/6/85, 3/7/85, 3/24/85, 4/16/85. - * - * Required system supported functions: - * scalb(x,n) - * copysign(x,y) - * logb(x) - * finite(x) - * - * Required kernel function: - * log__L(z) - * - * Method : - * 1. Argument Reduction: find k and f such that - * 1+x = 2^k * (1+f), - * where sqrt(2)/2 < 1+f < sqrt(2) . - * - * 2. Let s = f/(2+f) ; based on log(1+f) = log(1+s) - log(1-s) - * = 2s + 2/3 s**3 + 2/5 s**5 + ....., - * log(1+f) is computed by - * - * log(1+f) = 2s + s*log__L(s*s) - * where - * log__L(z) = z*(L1 + z*(L2 + z*(... (L6 + z*L7)...))) - * - * See log__L() for the values of the coefficients. - * - * 3. Finally, log(1+x) = k*ln2 + log(1+f). - * - * Remarks 1. In step 3 n*ln2 will be stored in two floating point numbers - * n*ln2hi + n*ln2lo, where ln2hi is chosen such that the last - * 20 bits (for VAX D format), or the last 21 bits ( for IEEE - * double) is 0. This ensures n*ln2hi is exactly representable. - * 2. In step 1, f may not be representable. A correction term c - * for f is computed. It follows that the correction term for - * f - t (the leading term of log(1+f) in step 2) is c-c*x. We - * add this correction term to n*ln2lo to attenuate the error. - * - * - * Special cases: - * log1p(x) is NaN with signal if x < -1; log1p(NaN) is NaN with no signal; - * log1p(INF) is +INF; log1p(-1) is -INF with signal; - * only log1p(0)=0 is exact for finite argument. - * - * Accuracy: - * log1p(x) returns the exact log(1+x) nearly rounded. In a test run - * with 1,536,000 random arguments on a VAX, the maximum observed - * error was .846 ulps (units in the last place). - * - * Constants: - * The hexadecimal values are the intended ones for the following constants. - * The decimal values may be used, provided that the compiler will convert - * from decimal to binary accurately enough to produce the hexadecimal values - * shown. - */ - -#include <errno.h> -#include "mathimpl.h" - -vc(ln2hi, 6.9314718055829871446E-1 ,7217,4031,0000,f7d0, 0, .B17217F7D00000) -vc(ln2lo, 1.6465949582897081279E-12 ,bcd5,2ce7,d9cc,e4f1, -39, .E7BCD5E4F1D9CC) -vc(sqrt2, 1.4142135623730950622E0 ,04f3,40b5,de65,33f9, 1, .B504F333F9DE65) - -ic(ln2hi, 6.9314718036912381649E-1, -1, 1.62E42FEE00000) -ic(ln2lo, 1.9082149292705877000E-10, -33, 1.A39EF35793C76) -ic(sqrt2, 1.4142135623730951455E0, 0, 1.6A09E667F3BCD) - -#ifdef vccast -#define ln2hi vccast(ln2hi) -#define ln2lo vccast(ln2lo) -#define sqrt2 vccast(sqrt2) -#endif - -double log1p(x) -double x; -{ - const static double zero=0.0, negone= -1.0, one=1.0, - half=1.0/2.0, small=1.0E-20; /* 1+small == 1 */ - double z,s,t,c; - int k; - -#if !defined(vax)&&!defined(tahoe) - if(x!=x) return(x); /* x is NaN */ -#endif /* !defined(vax)&&!defined(tahoe) */ - - if(finite(x)) { - if( x > negone ) { - - /* argument reduction */ - if(copysign(x,one)<small) return(x); - k=logb(one+x); z=scalb(x,-k); t=scalb(one,-k); - if(z+t >= sqrt2 ) - { k += 1 ; z *= half; t *= half; } - t += negone; x = z + t; - c = (t-x)+z ; /* correction term for x */ - - /* compute log(1+x) */ - s = x/(2+x); t = x*x*half; - c += (k*ln2lo-c*x); - z = c+s*(t+__log__L(s*s)); - x += (z - t) ; - - return(k*ln2hi+x); - } - /* end of if (x > negone) */ - - else { -#if defined(vax)||defined(tahoe) - if ( x == negone ) - return (infnan(-ERANGE)); /* -INF */ - else - return (infnan(EDOM)); /* NaN */ -#else /* defined(vax)||defined(tahoe) */ - /* x = -1, return -INF with signal */ - if ( x == negone ) return( negone/zero ); - - /* negative argument for log, return NaN with signal */ - else return ( zero / zero ); -#endif /* defined(vax)||defined(tahoe) */ - } - } - /* end of if (finite(x)) */ - - /* log(-INF) is NaN */ - else if(x<0) - return(zero/zero); - - /* log(+INF) is INF */ - else return(x); -} |