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authorAlon Zakai <alonzakai@gmail.com>2014-01-13 16:55:19 -0800
committerAlon Zakai <alonzakai@gmail.com>2014-01-13 16:56:03 -0800
commitcd1edebb5034ea52396a5b68304e84ae80878740 (patch)
tree6a6f8364ea74985d11c4f6ff74e5b80e08dc849d /system/lib/libc/musl/src/math/tgammal.c
parentaf59788f8b7b76515e36bee1bf66edf497b801db (diff)
parent2914deb17f3857bb02eeec87a58a3ed6d4a8853a (diff)
Merge branch 'incoming' of github.com:kripken/emscripten into incoming1.8.8
conflicts: tests/test_core.py tools/shared.py
Diffstat (limited to 'system/lib/libc/musl/src/math/tgammal.c')
-rw-r--r--system/lib/libc/musl/src/math/tgammal.c275
1 files changed, 275 insertions, 0 deletions
diff --git a/system/lib/libc/musl/src/math/tgammal.c b/system/lib/libc/musl/src/math/tgammal.c
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+/* origin: OpenBSD /usr/src/lib/libm/src/ld80/e_tgammal.c */
+/*
+ * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Gamma function
+ *
+ *
+ * SYNOPSIS:
+ *
+ * long double x, y, tgammal();
+ *
+ * y = tgammal( x );
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns gamma function of the argument. The result is
+ * correctly signed.
+ *
+ * Arguments |x| <= 13 are reduced by recurrence and the function
+ * approximated by a rational function of degree 7/8 in the
+ * interval (2,3). Large arguments are handled by Stirling's
+ * formula. Large negative arguments are made positive using
+ * a reflection formula.
+ *
+ *
+ * ACCURACY:
+ *
+ * Relative error:
+ * arithmetic domain # trials peak rms
+ * IEEE -40,+40 10000 3.6e-19 7.9e-20
+ * IEEE -1755,+1755 10000 4.8e-18 6.5e-19
+ *
+ * Accuracy for large arguments is dominated by error in powl().
+ *
+ */
+
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double tgammal(long double x)
+{
+ return tgamma(x);
+}
+#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+/*
+tgamma(x+2) = tgamma(x+2) P(x)/Q(x)
+0 <= x <= 1
+Relative error
+n=7, d=8
+Peak error = 1.83e-20
+Relative error spread = 8.4e-23
+*/
+static const long double P[8] = {
+ 4.212760487471622013093E-5L,
+ 4.542931960608009155600E-4L,
+ 4.092666828394035500949E-3L,
+ 2.385363243461108252554E-2L,
+ 1.113062816019361559013E-1L,
+ 3.629515436640239168939E-1L,
+ 8.378004301573126728826E-1L,
+ 1.000000000000000000009E0L,
+};
+static const long double Q[9] = {
+-1.397148517476170440917E-5L,
+ 2.346584059160635244282E-4L,
+-1.237799246653152231188E-3L,
+-7.955933682494738320586E-4L,
+ 2.773706565840072979165E-2L,
+-4.633887671244534213831E-2L,
+-2.243510905670329164562E-1L,
+ 4.150160950588455434583E-1L,
+ 9.999999999999999999908E-1L,
+};
+
+/*
+static const long double P[] = {
+-3.01525602666895735709e0L,
+-3.25157411956062339893e1L,
+-2.92929976820724030353e2L,
+-1.70730828800510297666e3L,
+-7.96667499622741999770e3L,
+-2.59780216007146401957e4L,
+-5.99650230220855581642e4L,
+-7.15743521530849602425e4L
+};
+static const long double Q[] = {
+ 1.00000000000000000000e0L,
+-1.67955233807178858919e1L,
+ 8.85946791747759881659e1L,
+ 5.69440799097468430177e1L,
+-1.98526250512761318471e3L,
+ 3.31667508019495079814e3L,
+ 1.60577839621734713377e4L,
+-2.97045081369399940529e4L,
+-7.15743521530849602412e4L
+};
+*/
+#define MAXGAML 1755.455L
+/*static const long double LOGPI = 1.14472988584940017414L;*/
+
+/* Stirling's formula for the gamma function
+tgamma(x) = sqrt(2 pi) x^(x-.5) exp(-x) (1 + 1/x P(1/x))
+z(x) = x
+13 <= x <= 1024
+Relative error
+n=8, d=0
+Peak error = 9.44e-21
+Relative error spread = 8.8e-4
+*/
+static const long double STIR[9] = {
+ 7.147391378143610789273E-4L,
+-2.363848809501759061727E-5L,
+-5.950237554056330156018E-4L,
+ 6.989332260623193171870E-5L,
+ 7.840334842744753003862E-4L,
+-2.294719747873185405699E-4L,
+-2.681327161876304418288E-3L,
+ 3.472222222230075327854E-3L,
+ 8.333333333333331800504E-2L,
+};
+
+#define MAXSTIR 1024.0L
+static const long double SQTPI = 2.50662827463100050242E0L;
+
+/* 1/tgamma(x) = z P(z)
+ * z(x) = 1/x
+ * 0 < x < 0.03125
+ * Peak relative error 4.2e-23
+ */
+static const long double S[9] = {
+-1.193945051381510095614E-3L,
+ 7.220599478036909672331E-3L,
+-9.622023360406271645744E-3L,
+-4.219773360705915470089E-2L,
+ 1.665386113720805206758E-1L,
+-4.200263503403344054473E-2L,
+-6.558780715202540684668E-1L,
+ 5.772156649015328608253E-1L,
+ 1.000000000000000000000E0L,
+};
+
+/* 1/tgamma(-x) = z P(z)
+ * z(x) = 1/x
+ * 0 < x < 0.03125
+ * Peak relative error 5.16e-23
+ * Relative error spread = 2.5e-24
+ */
+static const long double SN[9] = {
+ 1.133374167243894382010E-3L,
+ 7.220837261893170325704E-3L,
+ 9.621911155035976733706E-3L,
+-4.219773343731191721664E-2L,
+-1.665386113944413519335E-1L,
+-4.200263503402112910504E-2L,
+ 6.558780715202536547116E-1L,
+ 5.772156649015328608727E-1L,
+-1.000000000000000000000E0L,
+};
+
+static const long double PIL = 3.1415926535897932384626L;
+
+/* Gamma function computed by Stirling's formula.
+ */
+static long double stirf(long double x)
+{
+ long double y, w, v;
+
+ w = 1.0/x;
+ /* For large x, use rational coefficients from the analytical expansion. */
+ if (x > 1024.0)
+ w = (((((6.97281375836585777429E-5L * w
+ + 7.84039221720066627474E-4L) * w
+ - 2.29472093621399176955E-4L) * w
+ - 2.68132716049382716049E-3L) * w
+ + 3.47222222222222222222E-3L) * w
+ + 8.33333333333333333333E-2L) * w
+ + 1.0;
+ else
+ w = 1.0 + w * __polevll(w, STIR, 8);
+ y = expl(x);
+ if (x > MAXSTIR) { /* Avoid overflow in pow() */
+ v = powl(x, 0.5L * x - 0.25L);
+ y = v * (v / y);
+ } else {
+ y = powl(x, x - 0.5L) / y;
+ }
+ y = SQTPI * y * w;
+ return y;
+}
+
+long double tgammal(long double x)
+{
+ long double p, q, z;
+
+ if (!isfinite(x))
+ return x + INFINITY;
+
+ q = fabsl(x);
+ if (q > 13.0) {
+ if (x < 0.0) {
+ p = floorl(q);
+ z = q - p;
+ if (z == 0)
+ return 0 / z;
+ if (q > MAXGAML) {
+ z = 0;
+ } else {
+ if (z > 0.5) {
+ p += 1.0;
+ z = q - p;
+ }
+ z = q * sinl(PIL * z);
+ z = fabsl(z) * stirf(q);
+ z = PIL/z;
+ }
+ if (0.5 * p == floorl(q * 0.5))
+ z = -z;
+ } else if (x > MAXGAML) {
+ z = x * 0x1p16383L;
+ } else {
+ z = stirf(x);
+ }
+ return z;
+ }
+
+ z = 1.0;
+ while (x >= 3.0) {
+ x -= 1.0;
+ z *= x;
+ }
+ while (x < -0.03125L) {
+ z /= x;
+ x += 1.0;
+ }
+ if (x <= 0.03125L)
+ goto small;
+ while (x < 2.0) {
+ z /= x;
+ x += 1.0;
+ }
+ if (x == 2.0)
+ return z;
+
+ x -= 2.0;
+ p = __polevll(x, P, 7);
+ q = __polevll(x, Q, 8);
+ z = z * p / q;
+ return z;
+
+small:
+ /* z==1 if x was originally +-0 */
+ if (x == 0 && z != 1)
+ return x / x;
+ if (x < 0.0) {
+ x = -x;
+ q = z / (x * __polevll(x, SN, 8));
+ } else
+ q = z / (x * __polevll(x, S, 8));
+ return q;
+}
+#endif