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-rw-r--r--vendor/libm/src/math/k_cos.rs63
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diff --git a/vendor/libm/src/math/k_cos.rs b/vendor/libm/src/math/k_cos.rs
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+// origin: FreeBSD /usr/src/lib/msun/src/k_cos.c
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunSoft, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+
+const C1: f64 = 4.16666666666666019037e-02; /* 0x3FA55555, 0x5555554C */
+const C2: f64 = -1.38888888888741095749e-03; /* 0xBF56C16C, 0x16C15177 */
+const C3: f64 = 2.48015872894767294178e-05; /* 0x3EFA01A0, 0x19CB1590 */
+const C4: f64 = -2.75573143513906633035e-07; /* 0xBE927E4F, 0x809C52AD */
+const C5: f64 = 2.08757232129817482790e-09; /* 0x3E21EE9E, 0xBDB4B1C4 */
+const C6: f64 = -1.13596475577881948265e-11; /* 0xBDA8FAE9, 0xBE8838D4 */
+
+// kernel cos function on [-pi/4, pi/4], pi/4 ~ 0.785398164
+// Input x is assumed to be bounded by ~pi/4 in magnitude.
+// Input y is the tail of x.
+//
+// Algorithm
+// 1. Since cos(-x) = cos(x), we need only to consider positive x.
+// 2. if x < 2^-27 (hx<0x3e400000 0), return 1 with inexact if x!=0.
+// 3. cos(x) is approximated by a polynomial of degree 14 on
+// [0,pi/4]
+// 4 14
+// cos(x) ~ 1 - x*x/2 + C1*x + ... + C6*x
+// where the remez error is
+//
+// | 2 4 6 8 10 12 14 | -58
+// |cos(x)-(1-.5*x +C1*x +C2*x +C3*x +C4*x +C5*x +C6*x )| <= 2
+// | |
+//
+// 4 6 8 10 12 14
+// 4. let r = C1*x +C2*x +C3*x +C4*x +C5*x +C6*x , then
+// cos(x) ~ 1 - x*x/2 + r
+// since cos(x+y) ~ cos(x) - sin(x)*y
+// ~ cos(x) - x*y,
+// a correction term is necessary in cos(x) and hence
+// cos(x+y) = 1 - (x*x/2 - (r - x*y))
+// For better accuracy, rearrange to
+// cos(x+y) ~ w + (tmp + (r-x*y))
+// where w = 1 - x*x/2 and tmp is a tiny correction term
+// (1 - x*x/2 == w + tmp exactly in infinite precision).
+// The exactness of w + tmp in infinite precision depends on w
+// and tmp having the same precision as x. If they have extra
+// precision due to compiler bugs, then the extra precision is
+// only good provided it is retained in all terms of the final
+// expression for cos(). Retention happens in all cases tested
+// under FreeBSD, so don't pessimize things by forcibly clipping
+// any extra precision in w.
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub(crate) fn k_cos(x: f64, y: f64) -> f64 {
+ let z = x * x;
+ let w = z * z;
+ let r = z * (C1 + z * (C2 + z * C3)) + w * w * (C4 + z * (C5 + z * C6));
+ let hz = 0.5 * z;
+ let w = 1.0 - hz;
+ w + (((1.0 - w) - hz) + (z * r - x * y))
+}