diff --git a/src/lisp/GNUmakefile b/src/lisp/GNUmakefile index d8fb69002dcc6352825cbb29c71e1385bce50ae3..f67a20e7e10a41ed029cb85df2b44d513635d775 100644 --- a/src/lisp/GNUmakefile +++ b/src/lisp/GNUmakefile @@ -13,7 +13,8 @@ FDLIBM = k_sin.c k_cos.c k_tan.c s_sin.c s_cos.c s_tan.c sincos.c \ e_atan2.c \ e_rem_pio2.c k_rem_pio2.c \ e_log10.c s_scalbn.c \ - setexception.c + setexception.c \ + log2.c SRCS = lisp.c coreparse.c alloc.c monitor.c print.c interr.c \ vars.c parse.c interrupt.c search.c validate.c globals.c \ diff --git a/src/lisp/log2.c b/src/lisp/log2.c new file mode 100644 index 0000000000000000000000000000000000000000..d56bc43242bec3270aaa0c46d54cebacb2111f2f --- /dev/null +++ b/src/lisp/log2.c @@ -0,0 +1,139 @@ +/* + * ==================================================== + * Copyright (C) 2004 by Sun Microsystems, Inc. All rights reserved. + * + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +/* + * This is the log2 algorithm pulled out of __ieee754_pow in e_pow.c + */ + +/* + * Method: Let x = 2 * (1+f) + * 1. Compute and return log2(x) in two pieces: + * log2(x) = w1 + w2, + * where w1 has 53-24 = 29 bit trailing zeros. + */ + +#include "fdlibm.h" + +static double +bp[] = {1.0, 1.5,}, +dp_h[] = { 0.0, 5.84962487220764160156e-01,}, /* 0x3FE2B803, 0x40000000 */ +dp_l[] = { 0.0, 1.35003920212974897128e-08,}, /* 0x3E4CFDEB, 0x43CFD006 */ +zero = 0.0, +one = 1.0, +two53 = 9007199254740992.0, /* 0x43400000, 0x00000000 */ + /* poly coefs for (3/2)*(log(x)-2s-2/3*s**3 */ +L1 = 5.99999999999994648725e-01, /* 0x3FE33333, 0x33333303 */ +L2 = 4.28571428578550184252e-01, /* 0x3FDB6DB6, 0xDB6FABFF */ +L3 = 3.33333329818377432918e-01, /* 0x3FD55555, 0x518F264D */ +L4 = 2.72728123808534006489e-01, /* 0x3FD17460, 0xA91D4101 */ +L5 = 2.30660745775561754067e-01, /* 0x3FCD864A, 0x93C9DB65 */ +L6 = 2.06975017800338417784e-01, /* 0x3FCA7E28, 0x4A454EEF */ +cp = 9.61796693925975554329e-01, /* 0x3FEEC709, 0xDC3A03FD =2/(3ln2) */ +cp_h = 9.61796700954437255859e-01, /* 0x3FEEC709, 0xE0000000 =(float)cp */ +cp_l = -7.02846165095275826516e-09; /* 0xBE3E2FE0, 0x145B01F5 =tail of cp_h*/ + +double cmucl_log2(double x) +{ + double ax; + int k, hx, lx, ix; + union { int i[2]; double d; } ux; + + ux.d = x; + hx = ux.i[HIWORD]; lx = ux.i[LOWORD]; + ix = hx&0x7fffffff; + + ax = fabs(x); + + /* special value of x */ + + if (hx < 0x00100000) { /* x < 2**-1022 */ + if (((hx&0x7fffffff)|lx)==0) { + /* log(+-0)=-inf */ + return fdlibm_setexception(-1.0, FDLIBM_DIVIDE_BY_ZERO); + } + + if (hx<0) { + /* log(-#) = NaN */ + return fdlibm_setexception(x, FDLIBM_INVALID); + } + } + + { + double ss,s2,s_h,s_l,t_h,t_l; + double z_h,z_l,p_h,p_l; + double r, u, v, t, t1, t2; + int n, j; + + n = 0; + /* take care subnormal number */ + if(ix<0x00100000) { + ax *= two53; + n -= 53; + ux.d = ax; + ix = ux.i[HIWORD]; + } + n += ((ix)>>20)-0x3ff; + j = ix&0x000fffff; + /* determine interval */ + ix = j|0x3ff00000; /* normalize ix */ + if(j<=0x3988E) k=0; /* |x|<sqrt(3/2) */ + else if(j<0xBB67A) k=1; /* |x|<sqrt(3) */ + else {k=0;n+=1;ix -= 0x00100000;} + ux.d = ax; + ux.i[HIWORD] = ix; + ax = ux.d; + + /* compute ss = s_h+s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5) */ + u = ax-bp[k]; /* bp[0]=1.0, bp[1]=1.5 */ + v = one/(ax+bp[k]); + ss = u*v; + s_h = ss; + ux.d = s_h; + ux.i[LOWORD] = 0; + s_h = ux.d; + /* t_h=ax+bp[k] High */ + t_h = zero; + ux.d = t_h; + ux.i[HIWORD]=((ix>>1)|0x20000000)+0x00080000+(k<<18); + t_h = ux.d; + t_l = ax - (t_h-bp[k]); + s_l = v*((u-s_h*t_h)-s_h*t_l); + /* compute log(ax) */ + s2 = ss*ss; + r = s2*s2*(L1+s2*(L2+s2*(L3+s2*(L4+s2*(L5+s2*L6))))); + r += s_l*(s_h+ss); + s2 = s_h*s_h; + t_h = 3.0+s2+r; + ux.d = t_h; + ux.i[LOWORD] = 0; + t_h = ux.d; + t_l = r-((t_h-3.0)-s2); + /* u+v = ss*(1+...) */ + u = s_h*t_h; + v = s_l*t_h+t_l*ss; + /* 2/(3log2)*(ss+...) */ + p_h = u+v; + ux.d = p_h; + ux.i[LOWORD] = 0; + p_h = ux.d; + p_l = v-(p_h-u); + z_h = cp_h*p_h; /* cp_h+cp_l = 2/(3*log2) */ + z_l = cp_l*p_h+p_l*cp+dp_l[k]; + /* log2(ax) = (ss+..)*2/(3*log2) = n + dp_h + z_h + z_l */ + t = (double)n; + t1 = (((z_h+z_l)+dp_h[k])+t); + ux.d = t1; + ux.i[LOWORD] = 0; + t1 = ux.d; + t2 = z_l-(((t1-t)-dp_h[k])-z_h); + + return t1 + t2; + } +}