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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 | 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 3524x 3524x 3524x 3524x 3524x 3524x 3524x 3524x 3524x 3524x 1x 1x 3523x 3524x 1x 1x 3522x 3524x 307x 307x 3215x 3524x 110x 110x 110x 110x 110x 109x 104x 104x 104x 104x 101x 101x 3x 3x 3x 104x 2x 2x 104x 104x 5x 5x 4x 4x 1x 1x 1x 1x 109x 110x 110x 3524x 1x 1x 3106x 3524x 1106x 1106x 1x 1x 1105x 1105x 1105x 1105x 1105x 1105x 1106x 106x 106x 106x 106x 103x 103x 3x 3x 999x 999x 3524x 21x 21x 21x 21x 21x 21x 3524x 41x 41x 41x 41x 3524x 80x 80x 80x 3524x 120x 120x 120x 3524x 320x 320x 320x 3524x 840x 840x 840x 578x 578x 3524x 1x 1x 1x 1x 1x | /** * @license Apache-2.0 * * Copyright (c) 2018 The Stdlib Authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * * ## Notice * * The original C++ code and copyright notice are from the [Boost library]{@link http://www.boost.org/doc/libs/1_85_0/boost/math/special_functions/zeta.hpp}. The implementation follows the original, but has been modified for JavaScript. * * ```text * (C) Copyright John Maddock 2006. * * Use, modification and distribution are subject to the * Boost Software License, Version 1.0. (See accompanying file * LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt) * ``` */ 'use strict'; // MODULES // var isnan = require( '@stdlib/math/base/assert/is-nan' ); var isInteger = require( '@stdlib/math/base/assert/is-integer' ); var abs = require( '@stdlib/math/base/special/abs' ); var exp = require( '@stdlib/math/base/special/exp' ); var floor = require( '@stdlib/math/base/special/floor' ); var gamma = require( '@stdlib/math/base/special/gamma' ); var gammaln = require( '@stdlib/math/base/special/gammaln' ); var sinpi = require( '@stdlib/math/base/special/sinpi' ); var pow = require( '@stdlib/math/base/special/pow' ); var ln = require( '@stdlib/math/base/special/ln' ); var PINF = require( '@stdlib/constants/float64/pinf' ); var NINF = require( '@stdlib/constants/float64/ninf' ); var TWO_PI = require( '@stdlib/constants/float64/two-pi' ); var SQRT_EPSILON = require( '@stdlib/constants/float64/sqrt-eps' ); var LN_SQRT_TWO_PI = require( '@stdlib/constants/float64/ln-sqrt-two-pi' ); var MAX_SAFE_NTH_FACTORIAL = require( '@stdlib/constants/float64/max-safe-nth-factorial' ); var FLOAT64_MAX_LN = require( '@stdlib/constants/float64/max-ln' ); var ODD_POSITIVE_INTEGERS = require( './odd_positive_integers.json' ); var EVEN_NONNEGATIVE_INTEGERS = require( './even_nonnegative_integers.json' ); var BERNOULLI = require( './bernoulli.json' ); var rateval1 = require( './rational_p1q1.js' ); var rateval2 = require( './rational_p2q2.js' ); var rateval3 = require( './rational_p3q3.js' ); var rateval4 = require( './rational_p4q4.js' ); var rateval5 = require( './rational_p5q5.js' ); var rateval6 = require( './rational_p6q6.js' ); // VARIABLES // var MAX_BERNOULLI_2N = 129; var MAX_LN = floor( FLOAT64_MAX_LN ); var Y1 = 1.2433929443359375; var Y3 = 0.6986598968505859375; // MAIN // /** * Evaluates the Riemann zeta function. * * ## Method * * 1. First, we use the reflection formula * * ```tex * \zeta(1-s) = 2 \sin\biggl(\frac{\pi(1-s)}{2}\biggr)(2\pi^{-s})\Gamma(s)\zeta(s) * ``` * * to make \\(s\\) positive. * * 2. For \\(s \in (0,1)\\), we use the approximation * * ```tex * \zeta(s) = \frac{C + \operatorname{R}(1-s) - s}{1-s} * ``` * * with rational approximation \\(\operatorname{R}(1-z)\\) and constant \\(C\\). * * 3. For \\(s \in (1,4)\\), we use the approximation * * ```tex * \zeta(s) = C + \operatorname{R}(s-n) + \frac{1}{s-1} * ``` * * with rational approximation \\(\operatorname{R}(z-n)\\), constant \\(C\\), and integer \\(n\\). * * 4. For \\(s > 4\\), we use the approximation * * ```tex * \zeta(s) = 1 + e^{\operatorname{R}(z-n)} * ``` * * with rational approximation \\(\operatorname{R}(z-n)\\) and integer \\(n\\). * * 5. For negative odd integers, we use the closed form * * ```tex * \zeta(-n) = \frac{(-1)^n}{n+1} B_{n+1} * ``` * * where \\(B_{n+1}\\) is a Bernoulli number. * * 6. For negative even integers, we use the closed form * * ```tex * \zeta(-2n) = 0 * ``` * * 7. For nonnegative even integers, we could use the closed form * * ```tex * \zeta(2n) = \frac{(-1)^{n-1}2^{2n-1}\pi^{2n}}{(2n)!} B_{2n} * ``` * * where \\(B_{2n}\\) is a Bernoulli number. However, to speed computation, we use precomputed values (Wolfram Alpha). * * 8. For positive negative integers, we use precomputed values (Wolfram Alpha), as these values are useful for certain infinite series calculations. * * ## Notes * * - \\(\[\approx 1.5\mbox{e-}8, 1)\\) * * - max deviation: \\(2.020\mbox{e-}18\\) * - expected error: \\(-2.020\mbox{e-}18\\) * - max error found (double): \\(3.994987\mbox{e-}17\\) * * - \\(\[1,2\]\\) * * - max deviation: \\(9.007\mbox{e-}20\\) * - expected error: \\(9.007\mbox{e-}20\\) * * - \\((2,4\]\\) * * - max deviation: \\(5.946\mbox{e-}22\\) * - expected error: \\(-5.946\mbox{e-}22\\) * * - \\((4,7\]\\) * * - max deviation: \\(2.955\mbox{e-}17\\) * - expected error: \\(2.955\mbox{e-}17\\) * - max error found (double): \\(2.009135\mbox{e-}16\\) * * - \\((7,15)\\) * * - max deviation: \\(7.117\mbox{e-}16\\) * - expected error: \\(7.117\mbox{e-}16\\) * - max error found (double): \\(9.387771\mbox{e-}16\\) * * - \\(\[15,36)\\) * * - max error (in interpolated form): \\(1.668\mbox{e-}17\\) * - max error found (long double): \\(1.669714\mbox{e-}17\\) * * @param {number} s - input value * @returns {number} function value * * @example * var v = zeta( 1.1 ); * // returns ~10.584 * * @example * var v = zeta( -4.0 ); * // returns 0.0 * * @example * var v = zeta( 70.0 ); * // returns 1.0 * * @example * var v = zeta( 0.5 ); * // returns ~-1.46 * * @example * var v = zeta( 1.0 ); // pole * // returns NaN * * @example * var v = zeta( NaN ); * // returns NaN */ function zeta( s ) { var tmp; var sc; var as; var is; var r; var n; // Check for `NaN`: if ( isnan( s ) ) { return NaN; } // Check for a pole: if ( s === 1.0 ) { return NaN; } // Check for large value: if ( s >= 56.0 ) { return 1.0; } // Check for a closed form (integers): if ( isInteger( s ) ) { // Cast `s` to a 32-bit signed integer: is = s|0; // asm type annotation // Check that `s` does not exceed MAX_INT32: if ( is === s ) { if ( is < 0 ) { as = (-is)|0; // asm type annotation // Check if even negative integer: if ( (as&1) === 0 ) { return 0.0; } n = ( (as+1) / 2 )|0; // asm type annotation // Check if less than max Bernoulli number: if ( n <= MAX_BERNOULLI_2N ) { return -BERNOULLI[ n ] / (as+1.0); } // Fall through... } // Check if even nonnegative integer: else if ( (is&1) === 0 ) { return EVEN_NONNEGATIVE_INTEGERS[ is/2 ]; } // Must be a odd positive integer: else { return ODD_POSITIVE_INTEGERS[ (is-3)/2 ]; } } // Fall through... } if ( abs(s) < SQRT_EPSILON ) { return -0.5 - (LN_SQRT_TWO_PI * s); } sc = 1.0 - s; if ( s < 0.0 ) { // Check if even negative integer: if ( floor(s/2.0) === s/2.0 ) { return 0.0; } // Swap `s` and `sc`: tmp = s; s = sc; sc = tmp; // Determine if computation will overflow: if ( s > MAX_SAFE_NTH_FACTORIAL ) { tmp = sinpi( 0.5*sc ) * 2.0 * zeta( s ); r = gammaln( s ); r -= s * ln( TWO_PI ); if ( r > MAX_LN ) { return ( tmp < 0.0 ) ? NINF : PINF; } return tmp * exp( r ); } return sinpi( 0.5*sc ) * 2.0 * pow( TWO_PI, -s ) * gamma( s ) * zeta( s ); // eslint-disable-line max-len } if ( s < 1.0 ) { tmp = rateval1( sc ); tmp -= Y1; tmp += sc; tmp /= sc; return tmp; } if ( s <= 2.0 ) { sc = -sc; tmp = 1.0 / sc; return tmp + rateval2( sc ); } if ( s <= 4.0 ) { tmp = Y3 + ( 1.0 / (-sc) ); return tmp + rateval3( s-2.0 ); } if ( s <= 7.0 ) { tmp = rateval4( s-4.0 ); return 1.0 + exp( tmp ); } if ( s < 15.0 ) { tmp = rateval5( s-7.0 ); return 1.0 + exp( tmp ); } if ( s < 36.0 ) { tmp = rateval6( s-15.0 ); return 1.0 + exp( tmp ); } // s < 56 return 1.0 + pow( 2.0, -s ); } // EXPORTS // module.exports = zeta; |