Press n or j to go to the next uncovered block, b, p or k for the previous block.
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* @license Apache-2.0
*
* Copyright (c) 2025 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 following copyright and license were part of the original implementation available as part of [FreeBSD]{@link https://svnweb.freebsd.org/base/release/12.2.0/lib/msun/src/e_powf.c}. The implementation follows the original, but has been modified for JavaScript.
*
* ```text
* Copyright (C) 2004 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.
* ```
*/
'use strict';
// MODULES //
var fromWordf = require( '@stdlib/number/float32/base/from-word' );
var toWordf = require( '@stdlib/number/float32/base/to-word' );
var f32 = require( '@stdlib/number/float64/base/to-float32' );
var ldexpf = require( '@stdlib/math/base/special/ldexpf' );
var LN2 = require( '@stdlib/constants/float32/ln-two' );
var BIAS = require( '@stdlib/constants/float32/exponent-bias' );
var ABS_MASK = require( '@stdlib/constants/float32/abs-mask' );
var SIGNIFICAND_MASK = require( '@stdlib/constants/float32/significand-mask' );
var NUM_SIGNIFICAND_BITS = require( '@stdlib/constants/float32/num-significand-bits' );
var polyvalP = require( './polyval_p.js' );
// VARIABLES //
// 1.1754943508222875e-38 => 0 00000001 00000000000000000000000 => 0x00800000 = 8388608
var MIN_NORM_WORD = 0x00800000|0; // asm type annotation
// 0.5 => 0 01111110 00000000000000000000000 => 0x3f000000 = 1056964608
var HALF_WORD = 0x3f000000|0; // asm type annotation
// Mask to clear lower 15 significand bits:
var TRUNC_MASK_15 = 0xffff8000|0; // asm type annotation
// High: LN2
var LN2_HI = f32( 6.93145752e-01 ); // 0x3f317200
// Low: LN2
var LN2_LO = f32( 1.42860654e-06 ); // 0x35bfbe8c
var ONE = f32( 1.0 );
var TWO = f32( 2.0 );
// MAIN //
/**
* Computes \\(2^{\mathrm{hp} + \mathrm{lp}\\).
*
* @private
* @param {number} j - word of `hp + lp`
* @param {number} hp - first power summand
* @param {number} lp - second power summand
* @returns {number} function value
*
* @example
* var z = pow2f( 1065961648, -0.3398475646972656, -0.000002438187359100815 );
* // returns ~0.79
*/
function pow2f( j, hp, lp ) {
var tmp;
var t1;
var t;
var r;
var u;
var v;
var w;
var z;
var n;
var i;
var k;
i = ( j & ABS_MASK ) |0; // asm type annotation
k = ((i>>NUM_SIGNIFICAND_BITS) - BIAS)|0; // asm type annotation
n = 0;
// `|z| > 0.5`, set `n = z+0.5`
if ( i > HALF_WORD ) {
n = (j + (MIN_NORM_WORD>>(k+1)))|0; // asm type annotation
k = (((n & ABS_MASK)>>NUM_SIGNIFICAND_BITS) - BIAS)|0; // new k for n
tmp = ((n & ~(SIGNIFICAND_MASK >> k)))|0; // asm type annotation
t = fromWordf( tmp );
n = (((n & SIGNIFICAND_MASK)|MIN_NORM_WORD) >> (NUM_SIGNIFICAND_BITS-k))|0; // eslint-disable-line max-len
if ( j < 0 ) {
n = -n;
}
hp = f32( hp - t );
}
t = f32( lp + hp );
tmp = toWordf( t )|0; // asm type annotation
t = fromWordf( tmp & TRUNC_MASK_15 );
u = f32( t * LN2_HI );
v = f32( f32( f32( lp - f32(t-hp) )*LN2 ) + f32( t*LN2_LO ) );
z = f32( u + v );
w = f32( v - f32( z - u ) );
t = f32( z * z );
t1 = f32( z - f32( t*polyvalP( t ) ) );
r = f32( f32( f32(z*t1) / f32(t1-TWO) ) - f32( w + f32(z*w) ) );
z = f32( ONE - f32(r - z) );
j = toWordf( z ) |0; // asm type annotation
j += ( (n>>>0) << NUM_SIGNIFICAND_BITS ) |0; // asm type annotation
// Check for subnormal output...
if ( (j>>NUM_SIGNIFICAND_BITS) <= 0 ) {
z = ldexpf( z, n );
} else {
z = fromWordf( j );
}
return z;
}
// EXPORTS //
module.exports = pow2f;
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