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* @license Apache-2.0
*
* Copyright (c) 2026 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 isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major' );
var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
var gswap = require( '@stdlib/blas/base/gswap' ).ndarray;
var accessors = require( './accessors.js' );
// MAIN //
/**
* Interchanges two rows of a matrix using alternative indexing semantics.
*
* @param {PositiveInteger} M - number of rows in `A`
* @param {PositiveInteger} N - number of columns in `A`
* @param {integer} i - index of the first row to interchange
* @param {integer} j - index of the second row to interchange
* @param {Collection} A - input matrix
* @param {integer} strideA1 - stride length for the first dimension of `A`
* @param {integer} strideA2 - stride length for the second dimension of `A`
* @param {NonNegativeInteger} offsetA - starting index for `A`
* @returns {Collection} `A`
*
* @example
* var A = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ]; // => [ [ 1.0, 2.0 ], [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]
*
* gswapRows( 3, 2, 0, 2, A, 2, 1, 0 );
* // A => [ 5.0, 6.0, 3.0, 4.0, 1.0, 2.0 ]
*
* @example
* var A = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ]; // => [ [ 1.0, 4.0 ], [ 2.0, 5.0 ], [ 3.0, 6.0 ] ]
*
* gswapRows( 3, 2, 0, 2, A, 1, 3, 0 );
* // A => [ 3.0, 2.0, 1.0, 6.0, 5.0, 4.0 ]
*/
function gswapRows( M, N, i, j, A, strideA1, strideA2, offsetA ) {
var da0;
var da1;
var S0;
var S1;
var vi;
var vj;
var pi;
var pj;
var ia;
var oa;
var i0;
var i1;
if ( M <= 0 || N <= 0 ) {
return A;
}
if ( i < 0 ) {
i += M;
}
if ( j < 0 ) {
j += M;
}
if ( i === j ) {
return A;
}
// Row-major...
if ( isRowMajor( [ strideA1, strideA2 ] ) ) {
gswap( N, A, strideA2, offsetA+(i*strideA1), A, strideA2, offsetA+(j*strideA1) ); // eslint-disable-line max-len
return A;
}
// Column-major...
oa = arraylike2object( A );
if ( oa.accessorProtocol ) {
accessors( M, N, i, j, oa, strideA1, strideA2, offsetA );
return A;
}
S0 = M;
S1 = N;
// Resolve loop offsets:
da0 = strideA1;
da1 = strideA2 - ( S0*strideA1 );
ia = offsetA;
for ( i1 = 0; i1 < S1; i1++ ) {
// Scan down the rows in a column to find elements at rows `i` and `j`...
for ( i0 = 0; i0 < S0; i0++ ) {
if ( i0 === i ) {
vi = A[ ia ];
pi = ia;
}
if ( i0 === j ) {
vj = A[ ia ];
pj = ia;
}
ia += da0;
}
A[ pi ] = vj;
A[ pj ] = vi;
ia += da1;
}
return A;
}
// EXPORTS //
module.exports = gswapRows;
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