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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.
*/
'use strict';
// MODULES //
var float64ToFloat32 = require( '@stdlib/number/float64/base/to-float32' );
var absf = require( '@stdlib/math/base/special/absf' );
var isnanf = require( '@stdlib/math/base/assert/is-nanf' );
// VARIABLES //
var GAM = 4096.0;
var GAM_SQ = 16777216.0;
var RGAM_SQ = 5.9604645e-8;
// MAIN //
/**
* Construct the parameters for a modified Givens plane rotation.
*
* @param {number} d1 - scaling factor for the first vector component
* @param {number} d2 - scaling factor for the second vector component
* @param {number} x1 - first component of the first vector
* @param {number} y1 - first component of the second vector
* @param {Float32Array} param - output array
* @param {integer} stride - index increment
* @param {NonNegativeInteger} offset - starting index
* @returns {Float32Array} - output array
*
* @example
* var Float32Array = require( '@stdlib/array/float32' );
*
* var out = srotmg( 5.0, 4.0, 1.0, -2.0, new Float32Array( 5 ), 1, 0 );
* // returns <Float32Array>[ 1.0, -0.625, 0.0, 0.0, -0.5 ]
*/
function srotmg( d1, d2, x1, y1, param, stride, offset ) {
var flag;
var temp;
var ad1;
var ad2;
var h11;
var h12;
var h21;
var h22;
var p1;
var p2;
var q1;
var q2;
var u;
if ( isnanf( d1 ) || isnanf( d2 ) || isnanf( x1 ) || isnanf( y1 ) ) {
param[ offset ] = NaN;
param[ offset + stride ] = NaN;
param[ offset + ( 2 * stride ) ] = NaN;
param[ offset + ( 3 * stride ) ] = NaN;
param[ offset + ( 4 * stride ) ] = NaN;
return param;
}
if ( d1 < 0.0 ) {
flag = -1.0;
h11 = 0.0;
h12 = 0.0;
h21 = 0.0;
h22 = 0.0;
d1 = 0.0;
d2 = 0.0;
x1 = 0.0;
} else {
p2 = d2 * y1;
if ( p2 === 0.0 ) {
flag = -2.0;
param[ offset ] = flag;
return param;
}
p1 = float64ToFloat32( d1 * x1 );
q2 = float64ToFloat32( p2 * y1 );
q1 = float64ToFloat32( p1 * x1 );
ad1 = absf( q1 );
ad2 = absf( q2 );
if ( ad1 > ad2 ) {
h21 = float64ToFloat32( -y1 / x1 );
h12 = float64ToFloat32( p2 / p1 );
u = float64ToFloat32( 1 - float64ToFloat32( h12 * h21 ) );
if ( u > 0.0 ) {
flag = 0.0;
d1 = float64ToFloat32( d1 / u );
d2 = float64ToFloat32( d2 / u );
x1 = float64ToFloat32( x1 * u );
}
} else if ( q2 < 0.0 ) {
flag = -1.0;
h11 = 0.0;
h12 = 0.0;
h21 = 0.0;
h22 = 0.0;
d1 = 0.0;
d2 = 0.0;
x1 = 0.0;
} else {
flag = 1.0;
h11 = float64ToFloat32( p1 / p2 );
h22 = float64ToFloat32( x1 / y1 );
u = float64ToFloat32( 1 + float64ToFloat32( h11 * h22 ) );
temp = float64ToFloat32( d2 / u );
d2 = float64ToFloat32( d1 / u );
d1 = temp;
x1 = float64ToFloat32( y1 * u );
}
if ( d1 !== 0.0 ) {
while ( ( d1 < RGAM_SQ ) || ( d1 > GAM_SQ ) ) {
if ( flag === 0.0 ) {
h11 = 1.0;
h22 = 1.0;
flag = -1.0;
} else {
h21 = -1.0;
h12 = 1.0;
flag = -1.0;
}
if ( d1 < RGAM_SQ ) {
d1 = float64ToFloat32( d1 * GAM * GAM );
x1 = float64ToFloat32( x1 / GAM );
h11 = float64ToFloat32( h11 / GAM );
h12 = float64ToFloat32( h12 / GAM );
} else {
d1 = float64ToFloat32( d1 / GAM * GAM );
x1 = float64ToFloat32( x1 * GAM );
h11 = float64ToFloat32( h11 * GAM );
h12 = float64ToFloat32( h12 * GAM );
}
}
}
if ( d2 !== 0.0 ) {
while ( ( absf( d2 ) < RGAM_SQ ) || ( absf( d2 ) > GAM_SQ ) ) {
if ( flag === 0.0 ) {
h11 = 1.0;
h22 = 1.0;
flag = -1.0;
} else {
h21 = -1.0;
h12 = 1.0;
flag = -1.0;
}
if ( absf( d2 ) < RGAM_SQ ) {
d2 = float64ToFloat32( d2 * GAM * GAM );
h21 = float64ToFloat32( h21 / GAM );
h22 = float64ToFloat32( h22 / GAM );
} else {
d2 = float64ToFloat32( d2 / GAM * GAM );
h21 = float64ToFloat32( h21 * GAM );
h22 = float64ToFloat32( h22 * GAM );
}
}
}
}
param[ offset ] = flag;
if ( flag < 0.0 ) {
param[ offset + stride ] = h11;
param[ offset + ( 2 * stride ) ] = h21;
param[ offset + ( 3 * stride ) ] = h12;
param[ offset + ( 4 * stride ) ] = h22;
} else if ( flag === 0.0 ) {
param[ offset + ( 2 * stride ) ] = h21;
param[ offset + ( 3 * stride ) ] = h12;
} else {
param[ offset + stride ] = h11;
param[ offset + ( 4 * stride ) ] = h22;
}
param[ offset ] = flag;
return param;
}
// EXPORTS //
module.exports = srotmg;
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