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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 dswap = require( '@stdlib/blas/base/dswap' ).ndarray;
var trunc = require( '@stdlib/math/base/special/trunc' );
// MAIN //
/**
* Swaps the rows of a matrix `V` according to the permutation specified by the `scale` array.
*
* @private
* @param {NonNegativeInteger} N - number of rows in matrix `V`
* @param {NonNegativeInteger} M - number of columns in matrix `V`
* @param {NonNegativeInteger} ilo - index of leftmost column of the submatrix computed by `dgebal` (zero-based)
* @param {NonNegativeInteger} ihi - index of rightmost column of the submatrix computed by `dgebal` (zero-based)
* @param {Float64Array} scale - contains the details of the permutations and scaling factors applied when balancing `V`, computed by `dgebal`
* @param {integer} strideScale - stride of `scale`
* @param {NonNegativeInteger} offsetScale - starting index for `scale`
* @param {Float64Array} V - input matrix
* @param {integer} strideV1 - stride of the first dimension of `V`
* @param {integer} strideV2 - stride of the second dimension of `V`
* @param {NonNegativeInteger} offsetV - starting index for `V`
* @returns {void} manipulates `V` in place
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var scale = new Float64Array( [ 2.0, 1.0, 0.0 ] );
* var V = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
*
* swaps( 3, 2, 0, 1, scale, 1, 0, V, 2, 1, 0 );
* // V => <Float64Array>[ 5, 6, 3, 4, 1, 2 ]
*/
function swaps( N, M, ilo, ihi, scale, strideScale, offsetScale, V, strideV1, strideV2, offsetV ) { // eslint-disable-line max-len, max-params
var ii;
var k;
var i;
for ( ii = 0; ii < N; ii++ ) {
i = ii;
if ( i >= ilo && i <= ihi ) {
continue;
}
if ( i < ilo ) {
i = ilo - ( ii + 1 ); // Use ii + 1 here to match fortran's 1 based implementation
}
k = trunc( scale[ offsetScale + (i * strideScale) ] ); // K = int ( scale[ i ] )
if ( k === i ) {
continue;
}
dswap( M, V, strideV2, offsetV + (i * strideV1), V, strideV2, offsetV + (k * strideV1) ); // eslint-disable-line max-len
}
}
// EXPORTS //
module.exports = swaps;
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