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-/* log10l.c
- *
- * Common logarithm, long double precision
- *
- *
- *
- * SYNOPSIS:
- *
- * long double x, y, log10l();
- *
- * y = log10l( x );
- *
- *
- *
- * DESCRIPTION:
- *
- * Returns the base 10 logarithm of x.
- *
- * The argument is separated into its exponent and fractional
- * parts. If the exponent is between -1 and +1, the logarithm
- * of the fraction is approximated by
- *
- * log(1+x) = x - 0.5 x**2 + x**3 P(x)/Q(x).
- *
- * Otherwise, setting z = 2(x-1)/x+1),
- *
- * log(x) = z + z**3 P(z)/Q(z).
- *
- *
- *
- * ACCURACY:
- *
- * Relative error:
- * arithmetic domain # trials peak rms
- * IEEE 0.5, 2.0 30000 9.0e-20 2.6e-20
- * IEEE exp(+-10000) 30000 6.0e-20 2.3e-20
- *
- * In the tests over the interval exp(+-10000), the logarithms
- * of the random arguments were uniformly distributed over
- * [-10000, +10000].
- *
- * ERROR MESSAGES:
- *
- * log singularity: x = 0; returns MINLOG
- * log domain: x < 0; returns MINLOG
- */
-
-/*
-Cephes Math Library Release 2.2: January, 1991
-Copyright 1984, 1991 by Stephen L. Moshier
-Direct inquiries to 30 Frost Street, Cambridge, MA 02140
-*/
-
-#include <math.h>
-static char fname[] = {"log10l"};
-
-/* Coefficients for log(1+x) = x - x**2/2 + x**3 P(x)/Q(x)
- * 1/sqrt(2) <= x < sqrt(2)
- * Theoretical peak relative error = 6.2e-22
- */
-#ifdef UNK
-static long double P[] = {
- 4.9962495940332550844739E-1L,
- 1.0767376367209449010438E1L,
- 7.7671073698359539859595E1L,
- 2.5620629828144409632571E2L,
- 4.2401812743503691187826E2L,
- 3.4258224542413922935104E2L,
- 1.0747524399916215149070E2L,
-};
-static long double Q[] = {
-/* 1.0000000000000000000000E0,*/
- 2.3479774160285863271658E1L,
- 1.9444210022760132894510E2L,
- 7.7952888181207260646090E2L,
- 1.6911722418503949084863E3L,
- 2.0307734695595183428202E3L,
- 1.2695660352705325274404E3L,
- 3.2242573199748645407652E2L,
-};
-#endif
-
-#ifdef IBMPC
-static short P[] = {
-0xfe72,0xce22,0xd7b9,0xffce,0x3ffd, XPD
-0xb778,0x0e34,0x2c71,0xac47,0x4002, XPD
-0xea8b,0xc751,0x96f8,0x9b57,0x4005, XPD
-0xfeaf,0x6a02,0x67fb,0x801a,0x4007, XPD
-0x6b5a,0xf252,0x51ff,0xd402,0x4007, XPD
-0x39ce,0x9f76,0x8704,0xab4a,0x4007, XPD
-0x1b39,0x740b,0x532e,0xd6f3,0x4005, XPD
-};
-static short Q[] = {
-/*0x0000,0x0000,0x0000,0x8000,0x3fff,*/
-0x2f3a,0xbf26,0x93d5,0xbbd6,0x4003, XPD
-0x13c8,0x031a,0x2d7b,0xc271,0x4006, XPD
-0x449d,0x1993,0xd933,0xc2e1,0x4008, XPD
-0x5b65,0x574e,0x8301,0xd365,0x4009, XPD
-0xa65d,0x3bd2,0xc043,0xfdd8,0x4009, XPD
-0x3b21,0xffea,0x1cf5,0x9eb2,0x4009, XPD
-0x545c,0xd708,0x7e62,0xa136,0x4007, XPD
-};
-#endif
-
-#ifdef MIEEE
-static long P[] = {
-0x3ffd0000,0xffced7b9,0xce22fe72,
-0x40020000,0xac472c71,0x0e34b778,
-0x40050000,0x9b5796f8,0xc751ea8b,
-0x40070000,0x801a67fb,0x6a02feaf,
-0x40070000,0xd40251ff,0xf2526b5a,
-0x40070000,0xab4a8704,0x9f7639ce,
-0x40050000,0xd6f3532e,0x740b1b39,
-};
-static long Q[] = {
-/*0x3fff0000,0x80000000,0x00000000,*/
-0x40030000,0xbbd693d5,0xbf262f3a,
-0x40060000,0xc2712d7b,0x031a13c8,
-0x40080000,0xc2e1d933,0x1993449d,
-0x40090000,0xd3658301,0x574e5b65,
-0x40090000,0xfdd8c043,0x3bd2a65d,
-0x40090000,0x9eb21cf5,0xffea3b21,
-0x40070000,0xa1367e62,0xd708545c,
-};
-#endif
-
-/* Coefficients for log(x) = z + z^3 P(z^2)/Q(z^2),
- * where z = 2(x-1)/(x+1)
- * 1/sqrt(2) <= x < sqrt(2)
- * Theoretical peak relative error = 6.16e-22
- */
-
-#ifdef UNK
-static long double R[4] = {
- 1.9757429581415468984296E-3L,
--7.1990767473014147232598E-1L,
- 1.0777257190312272158094E1L,
--3.5717684488096787370998E1L,
-};
-static long double S[4] = {
-/* 1.00000000000000000000E0L,*/
--2.6201045551331104417768E1L,
- 1.9361891836232102174846E2L,
--4.2861221385716144629696E2L,
-};
-/* log10(2) */
-#define L102A 0.3125L
-#define L102B -1.1470004336018804786261e-2L
-/* log10(e) */
-#define L10EA 0.5L
-#define L10EB -6.5705518096748172348871e-2L
-#endif
-#ifdef IBMPC
-static short R[] = {
-0x6ef4,0xf922,0x7763,0x817b,0x3ff6, XPD
-0x15fd,0x1af9,0xde8f,0xb84b,0xbffe, XPD
-0x8b96,0x4f8d,0xa53c,0xac6f,0x4002, XPD
-0x8932,0xb4e3,0xe8ae,0x8ede,0xc004, XPD
-};
-static short S[] = {
-/*0x0000,0x0000,0x0000,0x8000,0x3fff,*/
-0x7ce4,0x1fc9,0xbdc5,0xd19b,0xc003, XPD
-0x0af3,0x0d10,0x716f,0xc19e,0x4006, XPD
-0x4d7d,0x0f55,0x5d06,0xd64e,0xc007, XPD
-};
-static short LG102A[] = {0x0000,0x0000,0x0000,0xa000,0x3ffd, XPD};
-#define L102A *(long double *)LG102A
-static short LG102B[] = {0x0cee,0x8601,0xaf60,0xbbec,0xbff8, XPD};
-#define L102B *(long double *)LG102B
-static short LG10EA[] = {0x0000,0x0000,0x0000,0x8000,0x3ffe, XPD};
-#define L10EA *(long double *)LG10EA
-static short LG10EB[] = {0x39ab,0x235e,0x9d5b,0x8690,0xbffb, XPD};
-#define L10EB *(long double *)LG10EB
-#endif
-
-#ifdef MIEEE
-static long R[12] = {
-0x3ff60000,0x817b7763,0xf9226ef4,
-0xbffe0000,0xb84bde8f,0x1af915fd,
-0x40020000,0xac6fa53c,0x4f8d8b96,
-0xc0040000,0x8edee8ae,0xb4e38932,
-};
-static long S[9] = {
-/*0x3fff0000,0x80000000,0x00000000,*/
-0xc0030000,0xd19bbdc5,0x1fc97ce4,
-0x40060000,0xc19e716f,0x0d100af3,
-0xc0070000,0xd64e5d06,0x0f554d7d,
-};
-static long LG102A[] = {0x3ffd0000,0xa0000000,0x00000000};
-#define L102A *(long double *)LG102A
-static long LG102B[] = {0xbff80000,0xbbecaf60,0x86010cee};
-#define L102B *(long double *)LG102B
-static long LG10EA[] = {0x3ffe0000,0x80000000,0x00000000};
-#define L10EA *(long double *)LG10EA
-static long LG10EB[] = {0xbffb0000,0x86909d5b,0x235e39ab};
-#define L10EB *(long double *)LG10EB
-#endif
-
-
-#define SQRTH 0.70710678118654752440L
-#ifdef ANSIPROT
-extern long double frexpl ( long double, int * );
-extern long double ldexpl ( long double, int );
-extern long double polevll ( long double, void *, int );
-extern long double p1evll ( long double, void *, int );
-extern int isnanl ( long double );
-#else
-long double frexpl(), ldexpl(), polevll(), p1evll(), isnanl();
-#endif
-#ifdef INFINITIES
-extern long double INFINITYL;
-#endif
-#ifdef NANS
-extern long double NANL;
-#endif
-
-long double log10l(x)
-long double x;
-{
-long double y;
-VOLATILE long double z;
-int e;
-
-#ifdef NANS
-if( isnanl(x) )
- return(x);
-#endif
-/* Test for domain */
-if( x <= 0.0L )
- {
- if( x == 0.0L )
- {
- mtherr( fname, SING );
-#ifdef INFINITIES
- return(-INFINITYL);
-#else
- return( -4.9314733889673399399914e3L );
-#endif
- }
- else
- {
- mtherr( fname, DOMAIN );
-#ifdef NANS
- return(NANL);
-#else
- return( -4.9314733889673399399914e3L );
-#endif
- }
- }
-#ifdef INFINITIES
-if( x == INFINITYL )
- return(INFINITYL);
-#endif
-/* separate mantissa from exponent */
-
-/* Note, frexp is used so that denormal numbers
- * will be handled properly.
- */
-x = frexpl( x, &e );
-
-
-/* logarithm using log(x) = z + z**3 P(z)/Q(z),
- * where z = 2(x-1)/x+1)
- */
-if( (e > 2) || (e < -2) )
-{
-if( x < SQRTH )
- { /* 2( 2x-1 )/( 2x+1 ) */
- e -= 1;
- z = x - 0.5L;
- y = 0.5L * z + 0.5L;
- }
-else
- { /* 2 (x-1)/(x+1) */
- z = x - 0.5L;
- z -= 0.5L;
- y = 0.5L * x + 0.5L;
- }
-x = z / y;
-z = x*x;
-y = x * ( z * polevll( z, R, 3 ) / p1evll( z, S, 3 ) );
-goto done;
-}
-
-
-/* logarithm using log(1+x) = x - .5x**2 + x**3 P(x)/Q(x) */
-
-if( x < SQRTH )
- {
- e -= 1;
- x = ldexpl( x, 1 ) - 1.0L; /* 2x - 1 */
- }
-else
- {
- x = x - 1.0L;
- }
-z = x*x;
-y = x * ( z * polevll( x, P, 6 ) / p1evll( x, Q, 7 ) );
-y = y - ldexpl( z, -1 ); /* -0.5x^2 + ... */
-
-done:
-
-/* Multiply log of fraction by log10(e)
- * and base 2 exponent by log10(2).
- *
- * ***CAUTION***
- *
- * This sequence of operations is critical and it may
- * be horribly defeated by some compiler optimizers.
- */
-z = y * (L10EB);
-z += x * (L10EB);
-z += e * (L102B);
-z += y * (L10EA);
-z += x * (L10EA);
-z += e * (L102A);
-
-return( z );
-}