From owner-svn-src-head@FreeBSD.ORG Mon Mar 7 03:11:28 2011 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 1C188106566B; Mon, 7 Mar 2011 03:11:28 +0000 (UTC) (envelope-from das@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id E496E8FC13; Mon, 7 Mar 2011 03:11:27 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.3/8.14.3) with ESMTP id p273BRJa019570; Mon, 7 Mar 2011 03:11:27 GMT (envelope-from das@svn.freebsd.org) Received: (from das@localhost) by svn.freebsd.org (8.14.3/8.14.3/Submit) id p273BR05019568; Mon, 7 Mar 2011 03:11:27 GMT (envelope-from das@svn.freebsd.org) Message-Id: <201103070311.p273BR05019568@svn.freebsd.org> From: David Schultz Date: Mon, 7 Mar 2011 03:11:27 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: svn commit: r219360 - head/lib/msun/src X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Mar 2011 03:11:28 -0000 Author: das Date: Mon Mar 7 03:11:27 2011 New Revision: 219360 URL: http://svn.freebsd.org/changeset/base/219360 Log: Convert log10() to use __kernel_log(), which is more accurate and simpler. Modified: head/lib/msun/src/e_log10.c Modified: head/lib/msun/src/e_log10.c ============================================================================== --- head/lib/msun/src/e_log10.c Mon Mar 7 03:09:24 2011 (r219359) +++ head/lib/msun/src/e_log10.c Mon Mar 7 03:11:27 2011 (r219360) @@ -14,45 +14,18 @@ #include __FBSDID("$FreeBSD$"); -/* __ieee754_log10(x) - * Return the base 10 logarithm of x - * - * Method : - * Let log10_2hi = leading 40 bits of log10(2) and - * log10_2lo = log10(2) - log10_2hi, - * ivln10 = 1/log(10) rounded. - * Then - * n = ilogb(x), - * if(n<0) n = n+1; - * x = scalbn(x,-n); - * log10(x) := n*log10_2hi + (n*log10_2lo + ivln10*log(x)) - * - * Note 1: - * To guarantee log10(10**n)=n, where 10**n is normal, the rounding - * mode must set to Round-to-Nearest. - * Note 2: - * [1/log(10)] rounded to 53 bits has error .198 ulps; - * log10 is monotonic at all binary break points. - * - * Special cases: - * log10(x) is NaN with signal if x < 0; - * log10(+INF) is +INF with no signal; log10(0) is -INF with signal; - * log10(NaN) is that NaN with no signal; - * log10(10**N) = N for N=0,1,...,22. - * - * 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. +/* + * Return the base 10 logarithm of x. See k_log.c for details on the algorithm. */ #include "math.h" #include "math_private.h" +#include "k_log.h" static const double two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ -ivln10 = 4.34294481903251816668e-01, /* 0x3FDBCB7B, 0x1526E50E */ +ivln10hi = 4.34294481878168880939e-01, /* 0x3fdbcb7b, 0x15200000 */ +ivln10lo = 2.50829467116452752298e-11, /* 0x3dbb9438, 0xca9aadd5 */ log10_2hi = 3.01029995663611771306e-01, /* 0x3FD34413, 0x509F6000 */ log10_2lo = 3.69423907715893078616e-13; /* 0x3D59FEF3, 0x11F12B36 */ @@ -61,7 +34,7 @@ static const double zero = 0.0; double __ieee754_log10(double x) { - double y,z; + double f,hi,lo,y,z; int32_t i,k,hx; u_int32_t lx; @@ -77,10 +50,15 @@ __ieee754_log10(double x) } if (hx >= 0x7ff00000) return x+x; k += (hx>>20)-1023; - i = ((u_int32_t)k&0x80000000)>>31; - hx = (hx&0x000fffff)|((0x3ff-i)<<20); - y = (double)(k+i); - SET_HIGH_WORD(x,hx); - z = y*log10_2lo + ivln10*__ieee754_log(x); + hx &= 0x000fffff; + i = (hx+0x95f64)&0x100000; + SET_HIGH_WORD(x,hx|(i^0x3ff00000)); /* normalize x or x/2 */ + k += (i>>20); + y = (double)k; + f = __kernel_log(x); + hi = x = x - 1; + SET_LOW_WORD(hi,0); + lo = x - hi; + z = y*log10_2lo + (x+f)*ivln10lo + (lo+f)*ivln10hi + hi*ivln10hi; return z+y*log10_2hi; }