All files / zrot/lib ndarray.js

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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 reinterpret = require( '@stdlib/strided/base/reinterpret-complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
 
 
// MAIN //
 
/**
* Applies a plane rotation with real cosine and complex sine.
*
* @param {PositiveInteger} N - number of indexed elements
* @param {Complex128Array} zx - first input array
* @param {integer} strideX - `zx` stride length
* @param {NonNegativeInteger} offsetX - starting `zx` index
* @param {Complex128Array} zy - second input array
* @param {integer} strideY - `zy` stride length
* @param {NonNegativeInteger} offsetY - starting `zy` index
* @param {number} c - cosine of the angle of rotation
* @param {Complex128} s - sine of the angle of rotation
* @returns {Complex128Array} `zy`
*
* @example
* var Complex128Array = require( '@stdlib/array/complex128' );
* var Complex128 = require( '@stdlib/complex/float64/ctor' );
*
* var zx = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
* var zy = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
* var s = new Complex128( 0.3, 0.4 );
*
* zrot( zx.length, zx, 1, 0, zy, 1, 0, 0.8, s );
*
* var z = zy.get( 0 );
* // returns <Complex128>[ ~-1.1, ~-0.2 ]
*
* z = zx.get( 0 );
* // returns <Complex128>[ ~0.8, ~1.6 ]
*/
function zrot( N, zx, strideX, offsetX, zy, strideY, offsetY, c, s ) {
	var viewX;
	var viewY;
	var sr;
	var si;
	var sx;
	var sy;
	var ix;
	var iy;
	var yr;
	var yi;
	var xr;
	var xi;
	var i;

	if ( N <= 0 ) {
		return zy;
	}
	viewX = reinterpret( zx, 0 );
	viewY = reinterpret( zy, 0 );

	ix = offsetX * 2;
	iy = offsetY * 2;

	sx = strideX * 2;
	sy = strideY * 2;

	sr = real( s );
	si = imag( s );

	for ( i = 0; i < N; i++ ) {
		yr = viewY[ iy ];
		yi = viewY[ iy+1 ];
		xr = viewX[ ix ];
		xi = viewX[ ix+1 ];

		// Compute tmp = c * zx[ ix ] + s * zy[ iy ]
		viewX[ ix ] = ( c*xr ) + ( ( sr*yr ) - ( si*yi ) );
		viewX[ ix+1 ] = ( c*xi ) + ( ( sr*yi ) + ( si*yr ) );

		// Compute zy[ iy ] = c * zy[ iy ] - conj(s) * zx[ ix ]
		viewY[ iy ] = ( c*yr ) - ( ( sr*xr ) + ( si*xi ) );
		viewY[ iy+1 ] = ( c*yi ) - ( ( sr*xi ) - ( si*xr ) );

		ix += sx;
		iy += sy;
	}
	return zy;
}
 
 
// EXPORTS //
 
module.exports = zrot;