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-/* logl.c
- *
- * Natural logarithm, long double precision
- *
- *
- *
- * SYNOPSIS:
- *
- * long double x, y, logl();
- *
- * y = logl( x );
- *
- *
- *
- * DESCRIPTION:
- *
- * Returns the base e (2.718...) 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 150000 8.71e-20 2.75e-20
- * IEEE exp(+-10000) 100000 5.39e-20 2.34e-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 -INFINITYL
- * log domain: x < 0; returns NANL
- */
-
-/*
-Cephes Math Library Release 2.7: May, 1998
-Copyright 1984, 1990, 1998 by Stephen L. Moshier
-*/
-
-#include <math.h>
-
-/* 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 = 2.32e-20
- */
-#ifdef UNK
-static long double P[] = {
- 4.5270000862445199635215E-5L,
- 4.9854102823193375972212E-1L,
- 6.5787325942061044846969E0L,
- 2.9911919328553073277375E1L,
- 6.0949667980987787057556E1L,
- 5.7112963590585538103336E1L,
- 2.0039553499201281259648E1L,
-};
-static long double Q[] = {
-/* 1.0000000000000000000000E0,*/
- 1.5062909083469192043167E1L,
- 8.3047565967967209469434E1L,
- 2.2176239823732856465394E2L,
- 3.0909872225312059774938E2L,
- 2.1642788614495947685003E2L,
- 6.0118660497603843919306E1L,
-};
-#endif
-
-#ifdef IBMPC
-static short P[] = {
-0x51b9,0x9cae,0x4b15,0xbde0,0x3ff0, XPD
-0x19cf,0xf0d4,0xc507,0xff40,0x3ffd, XPD
-0x9942,0xa7d2,0xfa37,0xd284,0x4001, XPD
-0x4add,0x65ce,0x9c5c,0xef4b,0x4003, XPD
-0x8445,0x619a,0x75c3,0xf3cc,0x4004, XPD
-0x81ab,0x3cd0,0xacba,0xe473,0x4004, XPD
-0x4cbf,0xcc18,0x016c,0xa051,0x4003, XPD
-};
-static short Q[] = {
-/*0x0000,0x0000,0x0000,0x8000,0x3fff,*/
-0xb8b7,0x81f1,0xacf4,0xf101,0x4002, XPD
-0xbc31,0x09a4,0x5a91,0xa618,0x4005, XPD
-0xaeec,0xe7da,0x2c87,0xddc3,0x4006, XPD
-0x2bde,0x4845,0xa2ee,0x9a8c,0x4007, XPD
-0x3120,0x4703,0x89f2,0xd86d,0x4006, XPD
-0x7347,0x3224,0x8223,0xf079,0x4004, XPD
-};
-#endif
-
-#ifdef MIEEE
-static long P[] = {
-0x3ff00000,0xbde04b15,0x9cae51b9,
-0x3ffd0000,0xff40c507,0xf0d419cf,
-0x40010000,0xd284fa37,0xa7d29942,
-0x40030000,0xef4b9c5c,0x65ce4add,
-0x40040000,0xf3cc75c3,0x619a8445,
-0x40040000,0xe473acba,0x3cd081ab,
-0x40030000,0xa051016c,0xcc184cbf,
-};
-static long Q[] = {
-/*0x3fff0000,0x80000000,0x00000000,*/
-0x40020000,0xf101acf4,0x81f1b8b7,
-0x40050000,0xa6185a91,0x09a4bc31,
-0x40060000,0xddc32c87,0xe7daaeec,
-0x40070000,0x9a8ca2ee,0x48452bde,
-0x40060000,0xd86d89f2,0x47033120,
-0x40040000,0xf0798223,0x32247347,
-};
-#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,
-};
-static long double C1 = 6.9314575195312500000000E-1L;
-static long double C2 = 1.4286068203094172321215E-6L;
-#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 sc1[] = {0x0000,0x0000,0x0000,0xb172,0x3ffe, XPD};
-#define C1 (*(long double *)sc1)
-static short sc2[] = {0x4f1e,0xcd5e,0x8e7b,0xbfbe,0x3feb, XPD};
-#define C2 (*(long double *)sc2)
-#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 sc1[] = {0x3ffe0000,0xb1720000,0x00000000};
-#define C1 (*(long double *)sc1)
-static long sc2[] = {0x3feb0000,0xbfbe8e7b,0xcd5e4f1e};
-#define C2 (*(long double *)sc2)
-#endif
-
-
-#define SQRTH 0.70710678118654752440L
-extern long double MINLOGL;
-#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 logl(x)
-long double x;
-{
-long double y, z;
-int e;
-
-#ifdef NANS
-if( isnanl(x) )
- return(x);
-#endif
-#ifdef INFINITIES
-if( x == INFINITYL )
- return(x);
-#endif
-/* Test for domain */
-if( x <= 0.0L )
- {
- if( x == 0.0L )
- {
-#ifdef INFINITIES
- return( -INFINITYL );
-#else
- mtherr( "logl", SING );
- return( MINLOGL );
-#endif
- }
- else
- {
-#ifdef NANS
- return( NANL );
-#else
- mtherr( "logl", DOMAIN );
- return( MINLOGL );
-#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;
-z = x * ( z * polevll( z, R, 3 ) / p1evll( z, S, 3 ) );
-z = z + e * C2;
-z = z + x;
-z = z + e * C1;
-return( z );
-}
-
-
-/* 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, 6 ) );
-y = y + e * C2;
-z = y - ldexpl( z, -1 ); /* y - 0.5 * z */
-/* Note, the sum of above terms does not exceed x/4,
- * so it contributes at most about 1/4 lsb to the error.
- */
-z = z + x;
-z = z + e * C1; /* This sum has an error of 1/2 lsb. */
-return( z );
-}