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try to fix rust-lang#170
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Signed-off-by: Benjamin Schultzer <benjamin@schultzer.com>
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@Schultzer
Schultzer committed Jul 3, 2019
1 parent fb0547e commit 66bb51a
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Showing 2 changed files with 67 additions and 63 deletions.
17 changes: 9 additions & 8 deletions src/math/jnf.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -75,14 +75,14 @@ pub fn jnf(n: i32, mut x: f32) -> f32 {
}
temp = 0.5 * x;
b = temp;
a = 1.0;
let mut a = 1;
i = 2;
while i <= nm1 + 1 {
a *= i as f32; /* a = n! */
a *= i; /* a = n! */
b *= temp; /* b = (x/2)^n */
i += 1;
}
b = b / a;
b /= a as f32;
} else {
/* use backward recurrence */
/* x x^2 x^2
Expand Down Expand Up @@ -124,7 +124,7 @@ pub fn jnf(n: i32, mut x: f32) -> f32 {
let mut k: i32;

nf = (nm1 as f32) + 1.0;
w = 2.0 * (nf as f32) / x;
w = 2.0 * nf / x;
h = 2.0 / x;
z = w + h;
q0 = w;
Expand Down Expand Up @@ -169,10 +169,10 @@ pub fn jnf(n: i32, mut x: f32) -> f32 {
b = 2.0 * (i as f32) * b / x - a;
a = temp;
/* scale b to avoid spurious overflow */
let x1p60 = f32::from_bits(0x5d800000); // 0x1p60 == 2^60
if b > x1p60 {
// let x1p60 = f32::from_bits(0x5d800000); // 0x1p60 == 2^60
if b > 1.152922e+18 {
a /= b;
t /= b;
t = t / b;
b = 1.0;
}
i -= 1;
Expand All @@ -182,8 +182,9 @@ pub fn jnf(n: i32, mut x: f32) -> f32 {
w = j1f(x);
if fabsf(z) >= fabsf(w) {
b = t * z / b;
// panic!("{:?} {:?} {:?} {:?} {:?} {:?}", t, z, w, b, f32::from_bits(0x5d800000), 1.152922e+18);
} else {
b = t * w / a;
b = t * (w / a);
}
}
}
Expand Down
113 changes: 58 additions & 55 deletions src/math/logf.rs
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Original file line number Diff line number Diff line change
@@ -1,66 +1,69 @@
/* origin: FreeBSD /usr/src/lib/msun/src/e_logf.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.
* ====================================================
*/
const LOGF_TABLE_BITS: u32 = 4;
const T: [(f64, f64); 16] = [(1.398907162146528e0, -3.3569133332882284e-1),
(1.3403141896637998e0, -2.929040563774074e-1),
(1.286432210124115e0, -2.518726580937369e-1),
(1.2367150214269895e0, -2.1245868807117255e-1),
(1.1906977166711752e0, -1.7453945183745634e-1),
(1.1479821020556429e0, -1.380057072319758e-1),
(1.1082251448272158e0, -1.0275976698545139e-1),
(1.0711297413057381e0, -6.871392447020525e-2),
(1.036437278977283e0, -3.57891387398228e-2),
(1e0, 0e0),
(9.492859795739057e-1, 5.204517742929496e-2),
(8.951049428609004e-1, 1.1081431298787942e-1),
(8.476821620351103e-1, 1.652495223695143e-1),
(8.050314851692001e-1, 2.1687389031699977e-1),
(7.664671008843108e-1, 2.659635028121397e-1),
(7.31428603316328e-1, 3.127556664073557e-1)];

const LN2_HI: f32 = 6.9313812256e-01; /* 0x3f317180 */
const LN2_LO: f32 = 9.0580006145e-06; /* 0x3717f7d1 */
/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
const LG1: f32 = 0.66666662693; /* 0xaaaaaa.0p-24*/
const LG2: f32 = 0.40000972152; /* 0xccce13.0p-25 */
const LG3: f32 = 0.28498786688; /* 0x91e9ee.0p-25 */
const LG4: f32 = 0.24279078841; /* 0xf89e26.0p-26 */
const A: [f64; 3] = [-2.5089342214237154e-1, 3.33456765744066e-1, -4.999997485802103e-1];
const LN2: f64 = 6.931471805599453e-1;
const N: u32 = (1 << LOGF_TABLE_BITS);
const OFF: u32 = 0x3f330000;

#[inline]
#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn logf(mut x: f32) -> f32 {
let x1p25 = f32::from_bits(0x4c000000); // 0x1p25f === 2 ^ 25

pub fn logf(x: f32) -> f32 {
let mut ix = x.to_bits();
let mut k = 0i32;

if (ix < 0x00800000) || ((ix >> 31) != 0) {
/* x < 2**-126 */
if ix << 1 == 0 {
return -1. / (x * x); /* log(+-0)=-inf */
}
if (ix >> 31) != 0 {
return (x - x) / 0.; /* log(-#) = NaN */
}
/* subnormal number, scale up x */
k -= 25;
x *= x1p25;
ix = x.to_bits();
} else if ix >= 0x7f800000 {
return x;
} else if ix == 0x3f800000 {
/* Fix sign of zero with downward rounding when x==1. */
if ix == 0x3f800000 {
return 0.;
}
if ix - 0x00800000 >= 0x7f800000 - 0x00800000 {
/* x < 0x1p-126 or inf or nan. */
if ix * 2 == 0 {
return -1. / 0.;
}
if ix == 0x7f800000 { /* log(inf) == inf. */
return x;
}
if (ix & 0x80000000) != 0 || ix * 2 >= 0xff000000 {
return (x - x) / (x - x);
}
/* x is subnormal, normalize it. */
ix = f32::to_bits(x * 8.388608e6);
ix -= 23 << 23;
}

/* x = 2^k z; where z is in range [OFF,2*OFF] and exact.
The range is split into N subintervals.
The ith subinterval contains z and c is near its center. */
let tmp = ix - OFF;
let i = (tmp >> (23 - LOGF_TABLE_BITS)) % N;
let k = tmp as i32 >> 23; /* arithmetic shift */
let iz = ix - (tmp & 0x1ff << 23);
let (invc, logc) = T[i as usize];
let z = f32::from_bits(iz) as f64;

/* reduce x into [sqrt(2)/2, sqrt(2)] */
ix += 0x3f800000 - 0x3f3504f3;
k += ((ix >> 23) as i32) - 0x7f;
ix = (ix & 0x007fffff) + 0x3f3504f3;
x = f32::from_bits(ix);
/* log(x) = log1p(z/c-1) + log(c) + k*Ln2 */
let r = z * invc - 1.;
let y0 = logc + k as f64 * LN2;

let f = x - 1.;
let s = f / (2. + f);
let z = s * s;
let w = z * z;
let t1 = w * (LG2 + w * LG4);
let t2 = z * (LG1 + w * LG3);
let r = t2 + t1;
let hfsq = 0.5 * f * f;
let dk = k as f32;
s * (hfsq + r) + dk * LN2_LO - hfsq + f + dk * LN2_HI
/* Pipelined polynomial evaluation to approximate log1p(r). */
let r2 = r * r;
let mut y = A[1] * r + A[2];
y = A[0] * r2 + y;
y = y * r2 + (y0 + r);
return y as f32;
}

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