stm: Add some floating-point math functions.
These have been taken from the musl library. It's a bit of a hack for now, just to get math functions working.
This commit is contained in:
Damien George
parent
f555d5deca
commit
849a0dda86
365
stm/math.c
365
stm/math.c
@ -1,3 +1,4 @@
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#include <stdint.h>
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#include <math.h>
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// these 2 functions seem to actually work... no idea why
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@ -29,12 +30,9 @@ float sqrtf(float x) {
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// TODO we need import these functions from some library (eg musl or newlib)
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float powf(float x, float y) { return 0.0; }
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float expf(float x) { return 0.0; }
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float logf(float x) { return 0.0; }
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float log2f(float x) { return 0.0; }
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float log10f(float x) { return 0.0; }
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float coshf(float x) { return 0.0; }
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float sinhf(float x) { return 0.0; }
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float tanhf(float x) { return 0.0; }
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float acoshf(float x) { return 0.0; }
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float asinhf(float x) { return 0.0; }
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@ -46,3 +44,364 @@ float acosf(float x) { return 0.0; }
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float asinf(float x) { return 0.0; }
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float atanf(float x) { return 0.0; }
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float atan2f(float x, float y) { return 0.0; }
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/*****************************************************************************/
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// from musl-0.9.15 libm.h
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/* origin: FreeBSD /usr/src/lib/msun/src/math_private.h */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#define FORCE_EVAL(x) do { \
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if (sizeof(x) == sizeof(float)) { \
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volatile float __x; \
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__x = (x); \
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(void)__x; \
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} else if (sizeof(x) == sizeof(double)) { \
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volatile double __x; \
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__x = (x); \
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(void)__x; \
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} else { \
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volatile long double __x; \
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__x = (x); \
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(void)__x; \
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} \
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} while(0)
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/* Get a 32 bit int from a float. */
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#define GET_FLOAT_WORD(w,d) \
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do { \
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union {float f; uint32_t i;} __u; \
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__u.f = (d); \
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(w) = __u.i; \
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} while (0)
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/* Set a float from a 32 bit int. */
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#define SET_FLOAT_WORD(d,w) \
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do { \
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union {float f; uint32_t i;} __u; \
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__u.i = (w); \
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(d) = __u.f; \
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} while (0)
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/*****************************************************************************/
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// scalbnf from musl-0.9.15
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float scalbnf(float x, int n)
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{
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union {float f; uint32_t i;} u;
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float_t y = x;
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if (n > 127) {
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y *= 0x1p127f;
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n -= 127;
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if (n > 127) {
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y *= 0x1p127f;
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n -= 127;
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if (n > 127)
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n = 127;
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}
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} else if (n < -126) {
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y *= 0x1p-126f;
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n += 126;
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if (n < -126) {
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y *= 0x1p-126f;
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n += 126;
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if (n < -126)
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n = -126;
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}
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}
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u.i = (uint32_t)(0x7f+n)<<23;
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x = y * u.f;
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return x;
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}
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/*****************************************************************************/
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// expf from musl-0.9.15
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/* origin: FreeBSD /usr/src/lib/msun/src/e_expf.c */
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/*
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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static const float
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half[2] = {0.5,-0.5},
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ln2hi = 6.9314575195e-1f, /* 0x3f317200 */
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ln2lo = 1.4286067653e-6f, /* 0x35bfbe8e */
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invln2 = 1.4426950216e+0f, /* 0x3fb8aa3b */
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/*
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* Domain [-0.34568, 0.34568], range ~[-4.278e-9, 4.447e-9]:
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* |x*(exp(x)+1)/(exp(x)-1) - p(x)| < 2**-27.74
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*/
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P1 = 1.6666625440e-1f, /* 0xaaaa8f.0p-26 */
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P2 = -2.7667332906e-3f; /* -0xb55215.0p-32 */
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float expf(float x)
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{
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float_t hi, lo, c, xx, y;
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int k, sign;
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uint32_t hx;
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GET_FLOAT_WORD(hx, x);
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sign = hx >> 31; /* sign bit of x */
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hx &= 0x7fffffff; /* high word of |x| */
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/* special cases */
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if (hx >= 0x42aeac50) { /* if |x| >= -87.33655f or NaN */
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if (hx >= 0x42b17218 && !sign) { /* x >= 88.722839f */
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/* overflow */
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x *= 0x1p127f;
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return x;
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}
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if (sign) {
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/* underflow */
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FORCE_EVAL(-0x1p-149f/x);
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if (hx >= 0x42cff1b5) /* x <= -103.972084f */
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return 0;
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}
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}
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/* argument reduction */
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if (hx > 0x3eb17218) { /* if |x| > 0.5 ln2 */
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if (hx > 0x3f851592) /* if |x| > 1.5 ln2 */
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k = invln2*x + half[sign];
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else
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k = 1 - sign - sign;
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hi = x - k*ln2hi; /* k*ln2hi is exact here */
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lo = k*ln2lo;
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x = hi - lo;
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} else if (hx > 0x39000000) { /* |x| > 2**-14 */
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k = 0;
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hi = x;
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lo = 0;
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} else {
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/* raise inexact */
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FORCE_EVAL(0x1p127f + x);
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return 1 + x;
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}
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/* x is now in primary range */
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xx = x*x;
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c = x - xx*(P1+xx*P2);
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y = 1 + (x*c/(2-c) - lo + hi);
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if (k == 0)
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return y;
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return scalbnf(y, k);
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}
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/*****************************************************************************/
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// expm1f from musl-0.9.15
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/* origin: FreeBSD /usr/src/lib/msun/src/s_expm1f.c */
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/*
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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static const float
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o_threshold = 8.8721679688e+01, /* 0x42b17180 */
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ln2_hi = 6.9313812256e-01, /* 0x3f317180 */
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ln2_lo = 9.0580006145e-06, /* 0x3717f7d1 */
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//invln2 = 1.4426950216e+00, /* 0x3fb8aa3b */
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/*
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* Domain [-0.34568, 0.34568], range ~[-6.694e-10, 6.696e-10]:
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* |6 / x * (1 + 2 * (1 / (exp(x) - 1) - 1 / x)) - q(x)| < 2**-30.04
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* Scaled coefficients: Qn_here = 2**n * Qn_for_q (see s_expm1.c):
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*/
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Q1 = -3.3333212137e-2, /* -0x888868.0p-28 */
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Q2 = 1.5807170421e-3; /* 0xcf3010.0p-33 */
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float expm1f(float x)
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{
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float_t y,hi,lo,c,t,e,hxs,hfx,r1,twopk;
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union {float f; uint32_t i;} u = {x};
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uint32_t hx = u.i & 0x7fffffff;
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int k, sign = u.i >> 31;
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/* filter out huge and non-finite argument */
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if (hx >= 0x4195b844) { /* if |x|>=27*ln2 */
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if (hx > 0x7f800000) /* NaN */
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return x;
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if (sign)
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return -1;
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if (x > o_threshold) {
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x *= 0x1p127f;
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return x;
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}
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}
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/* argument reduction */
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if (hx > 0x3eb17218) { /* if |x| > 0.5 ln2 */
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if (hx < 0x3F851592) { /* and |x| < 1.5 ln2 */
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if (!sign) {
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hi = x - ln2_hi;
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lo = ln2_lo;
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k = 1;
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} else {
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hi = x + ln2_hi;
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lo = -ln2_lo;
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k = -1;
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}
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} else {
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k = invln2*x + (sign ? -0.5f : 0.5f);
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t = k;
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hi = x - t*ln2_hi; /* t*ln2_hi is exact here */
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lo = t*ln2_lo;
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}
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x = hi-lo;
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c = (hi-x)-lo;
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} else if (hx < 0x33000000) { /* when |x|<2**-25, return x */
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if (hx < 0x00800000)
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FORCE_EVAL(x*x);
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return x;
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} else
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k = 0;
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/* x is now in primary range */
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hfx = 0.5f*x;
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hxs = x*hfx;
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r1 = 1.0f+hxs*(Q1+hxs*Q2);
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t = 3.0f - r1*hfx;
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e = hxs*((r1-t)/(6.0f - x*t));
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if (k == 0) /* c is 0 */
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return x - (x*e-hxs);
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e = x*(e-c) - c;
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e -= hxs;
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/* exp(x) ~ 2^k (x_reduced - e + 1) */
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if (k == -1)
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return 0.5f*(x-e) - 0.5f;
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if (k == 1) {
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if (x < -0.25f)
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return -2.0f*(e-(x+0.5f));
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return 1.0f + 2.0f*(x-e);
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}
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u.i = (0x7f+k)<<23; /* 2^k */
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twopk = u.f;
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if (k < 0 || k > 56) { /* suffice to return exp(x)-1 */
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y = x - e + 1.0f;
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if (k == 128)
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y = y*2.0f*0x1p127f;
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else
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y = y*twopk;
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return y - 1.0f;
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}
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u.i = (0x7f-k)<<23; /* 2^-k */
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if (k < 23)
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y = (x-e+(1-u.f))*twopk;
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else
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y = (x-(e+u.f)+1)*twopk;
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return y;
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}
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/*****************************************************************************/
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// __expo2f from musl-0.9.15
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/* k is such that k*ln2 has minimal relative error and x - kln2 > log(FLT_MIN) */
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static const int k = 235;
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static const float kln2 = 0x1.45c778p+7f;
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/* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */
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float __expo2f(float x)
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{
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float scale;
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/* note that k is odd and scale*scale overflows */
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SET_FLOAT_WORD(scale, (uint32_t)(0x7f + k/2) << 23);
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/* exp(x - k ln2) * 2**(k-1) */
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return expf(x - kln2) * scale * scale;
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}
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/*****************************************************************************/
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// coshf from musl-0.9.15
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float coshf(float x)
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{
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union {float f; uint32_t i;} u = {.f = x};
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uint32_t w;
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float t;
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/* |x| */
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u.i &= 0x7fffffff;
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x = u.f;
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w = u.i;
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/* |x| < log(2) */
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if (w < 0x3f317217) {
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if (w < 0x3f800000 - (12<<23)) {
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FORCE_EVAL(x + 0x1p120f);
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return 1;
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}
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t = expm1f(x);
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return 1 + t*t/(2*(1+t));
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}
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/* |x| < log(FLT_MAX) */
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if (w < 0x42b17217) {
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t = expf(x);
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return 0.5f*(t + 1/t);
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}
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/* |x| > log(FLT_MAX) or nan */
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t = __expo2f(x);
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return t;
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}
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/*****************************************************************************/
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// sinhf from musl-0.9.15
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float sinhf(float x)
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{
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union {float f; uint32_t i;} u = {.f = x};
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uint32_t w;
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float t, h, absx;
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h = 0.5;
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if (u.i >> 31)
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h = -h;
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/* |x| */
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u.i &= 0x7fffffff;
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absx = u.f;
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w = u.i;
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/* |x| < log(FLT_MAX) */
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if (w < 0x42b17217) {
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t = expm1f(absx);
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if (w < 0x3f800000) {
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if (w < 0x3f800000 - (12<<23))
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return x;
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return h*(2*t - t*t/(t+1));
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}
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return h*(t + t/(t+1));
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}
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/* |x| > logf(FLT_MAX) or nan */
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t = 2*h*__expo2f(absx);
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return t;
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}
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