diff options
Diffstat (limited to 'lib/mlibc/options/ansi/musl-generic-math/jnf.c')
| -rw-r--r-- | lib/mlibc/options/ansi/musl-generic-math/jnf.c | 202 |
1 files changed, 0 insertions, 202 deletions
diff --git a/lib/mlibc/options/ansi/musl-generic-math/jnf.c b/lib/mlibc/options/ansi/musl-generic-math/jnf.c deleted file mode 100644 index f63c062..0000000 --- a/lib/mlibc/options/ansi/musl-generic-math/jnf.c +++ /dev/null @@ -1,202 +0,0 @@ -/* origin: FreeBSD /usr/src/lib/msun/src/e_jnf.c */ -/* - * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. - */ -/* - * ==================================================== - * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. - * - * Developed at SunPro, a Sun Microsystems, Inc. business. - * Permission to use, copy, modify, and distribute this - * software is freely granted, provided that this notice - * is preserved. - * ==================================================== - */ - -#define _GNU_SOURCE -#include "libm.h" - -float jnf(int n, float x) -{ - uint32_t ix; - int nm1, sign, i; - float a, b, temp; - - GET_FLOAT_WORD(ix, x); - sign = ix>>31; - ix &= 0x7fffffff; - if (ix > 0x7f800000) /* nan */ - return x; - - /* J(-n,x) = J(n,-x), use |n|-1 to avoid overflow in -n */ - if (n == 0) - return j0f(x); - if (n < 0) { - nm1 = -(n+1); - x = -x; - sign ^= 1; - } else - nm1 = n-1; - if (nm1 == 0) - return j1f(x); - - sign &= n; /* even n: 0, odd n: signbit(x) */ - x = fabsf(x); - if (ix == 0 || ix == 0x7f800000) /* if x is 0 or inf */ - b = 0.0f; - else if (nm1 < x) { - /* Safe to use J(n+1,x)=2n/x *J(n,x)-J(n-1,x) */ - a = j0f(x); - b = j1f(x); - for (i=0; i<nm1; ){ - i++; - temp = b; - b = b*(2.0f*i/x) - a; - a = temp; - } - } else { - if (ix < 0x35800000) { /* x < 2**-20 */ - /* x is tiny, return the first Taylor expansion of J(n,x) - * J(n,x) = 1/n!*(x/2)^n - ... - */ - if (nm1 > 8) /* underflow */ - nm1 = 8; - temp = 0.5f * x; - b = temp; - a = 1.0f; - for (i=2; i<=nm1+1; i++) { - a *= (float)i; /* a = n! */ - b *= temp; /* b = (x/2)^n */ - } - b = b/a; - } else { - /* use backward recurrence */ - /* x x^2 x^2 - * J(n,x)/J(n-1,x) = ---- ------ ------ ..... - * 2n - 2(n+1) - 2(n+2) - * - * 1 1 1 - * (for large x) = ---- ------ ------ ..... - * 2n 2(n+1) 2(n+2) - * -- - ------ - ------ - - * x x x - * - * Let w = 2n/x and h=2/x, then the above quotient - * is equal to the continued fraction: - * 1 - * = ----------------------- - * 1 - * w - ----------------- - * 1 - * w+h - --------- - * w+2h - ... - * - * To determine how many terms needed, let - * Q(0) = w, Q(1) = w(w+h) - 1, - * Q(k) = (w+k*h)*Q(k-1) - Q(k-2), - * When Q(k) > 1e4 good for single - * When Q(k) > 1e9 good for double - * When Q(k) > 1e17 good for quadruple - */ - /* determine k */ - float t,q0,q1,w,h,z,tmp,nf; - int k; - - nf = nm1+1.0f; - w = 2*nf/x; - h = 2/x; - z = w+h; - q0 = w; - q1 = w*z - 1.0f; - k = 1; - while (q1 < 1.0e4f) { - k += 1; - z += h; - tmp = z*q1 - q0; - q0 = q1; - q1 = tmp; - } - for (t=0.0f, i=k; i>=0; i--) - t = 1.0f/(2*(i+nf)/x-t); - a = t; - b = 1.0f; - /* estimate log((2/x)^n*n!) = n*log(2/x)+n*ln(n) - * Hence, if n*(log(2n/x)) > ... - * single 8.8722839355e+01 - * double 7.09782712893383973096e+02 - * long double 1.1356523406294143949491931077970765006170e+04 - * then recurrent value may overflow and the result is - * likely underflow to zero - */ - tmp = nf*logf(fabsf(w)); - if (tmp < 88.721679688f) { - for (i=nm1; i>0; i--) { - temp = b; - b = 2.0f*i*b/x - a; - a = temp; - } - } else { - for (i=nm1; i>0; i--){ - temp = b; - b = 2.0f*i*b/x - a; - a = temp; - /* scale b to avoid spurious overflow */ - if (b > 0x1p60f) { - a /= b; - t /= b; - b = 1.0f; - } - } - } - z = j0f(x); - w = j1f(x); - if (fabsf(z) >= fabsf(w)) - b = t*z/b; - else - b = t*w/a; - } - } - return sign ? -b : b; -} - -float ynf(int n, float x) -{ - uint32_t ix, ib; - int nm1, sign, i; - float a, b, temp; - - GET_FLOAT_WORD(ix, x); - sign = ix>>31; - ix &= 0x7fffffff; - if (ix > 0x7f800000) /* nan */ - return x; - if (sign && ix != 0) /* x < 0 */ - return 0/0.0f; - if (ix == 0x7f800000) - return 0.0f; - - if (n == 0) - return y0f(x); - if (n < 0) { - nm1 = -(n+1); - sign = n&1; - } else { - nm1 = n-1; - sign = 0; - } - if (nm1 == 0) - return sign ? -y1f(x) : y1f(x); - - a = y0f(x); - b = y1f(x); - /* quit if b is -inf */ - GET_FLOAT_WORD(ib,b); - for (i = 0; i < nm1 && ib != 0xff800000; ) { - i++; - temp = b; - b = (2.0f*i/x)*b - a; - GET_FLOAT_WORD(ib, b); - a = temp; - } - return sign ? -b : b; -} |