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* @license Apache-2.0
*
* Copyright (c) 2024 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 floor = require( '@stdlib/math/base/special/floor' );
var sswap = require( '@stdlib/blas/base/sswap' ).ndarray;
// VARIABLES //
var BLOCK_SIZE = 32;
// MAIN //
/**
* Performs a series of row interchanges on a matrix `A` using pivot indices stored in `IPIV`.
*
* @private
* @param {PositiveInteger} N - number of columns in `A`
* @param {Float32Array} A - input matrix
* @param {integer} strideA1 - stride of the first dimension of `A`
* @param {integer} strideA2 - stride of the second dimension of `A`
* @param {NonNegativeInteger} offsetA - index offset for `A`
* @param {NonNegativeInteger} k1 - index of first row to interchange
* @param {NonNegativeInteger} k2 - index of last row to interchange
* @param {integer} inck - direction in which to apply pivots (-1 to apply pivots in reverse order; otherwise, apply in provided order)
* @param {Int32Array} IPIV - vector of pivot indices
* @param {integer} strideIPIV - `IPIV` stride length
* @param {NonNegativeInteger} offsetIPIV - index offset for `IPIV`
* @returns {Float32Array} permuted matrix `A`
*
* @example
* var Int32Array = require( '@stdlib/array/int32' );
* var Float32Array = require( '@stdlib/array/float32' );
*
* var IPIV = new Int32Array( [ 2, 0, 1 ] );
* var A = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] ); // => [ [ 1.0, 2.0 ], [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]
*
* slaswp( 2, A, 2, 1, 0, 0, 2, 1, IPIV, 1, 0 );
* // A => <Float32Array>[ 3.0, 4.0, 1.0, 2.0, 5.0, 6.0 ]
*/
function slaswp( N, A, strideA1, strideA2, offsetA, k1, k2, inck, IPIV, strideIPIV, offsetIPIV ) { // eslint-disable-line max-len, max-params
var nrows;
var n32;
var tmp;
var row;
var ia1;
var ia2;
var ip;
var i;
var j;
var k;
var n;
var o;
// Compute the number of rows to be interchanged:
if ( inck > 0 ) {
nrows = k2 - k1;
} else {
nrows = k1 - k2;
}
nrows += 1;
// If the order is row-major, we can delegate to the Level 1 routine `sswap` for interchanging rows...
if ( isRowMajor( [ strideA1, strideA2 ] ) ) {
ip = offsetIPIV;
for ( i = 0, k = k1; i < nrows; i++, k += inck ) {
row = IPIV[ ip ];
if ( row !== k ) {
sswap( N, A, strideA2, offsetA+(k*strideA1), A, strideA2, offsetA+(row*strideA1) ); // eslint-disable-line max-len
}
ip += strideIPIV;
}
return A;
}
// If the order is column-major, we need to use loop tiling to ensure efficient cache access when accessing matrix elements...
n32 = floor( N/BLOCK_SIZE ) * BLOCK_SIZE;
if ( n32 !== 0 ) {
for ( j = 0; j < n32; j += BLOCK_SIZE ) {
ip = offsetIPIV;
for ( i = 0, k = k1; i < nrows; i++, k += inck ) {
row = IPIV[ ip ];
if ( row !== k ) {
ia1 = offsetA + ( k*strideA1 );
ia2 = offsetA + ( row*strideA1 );
for ( n = j; n < j+BLOCK_SIZE; n++ ) {
o = n * strideA2;
tmp = A[ ia1+o ];
A[ ia1+o ] = A[ ia2+o ];
A[ ia2+o ] = tmp;
}
}
ip += strideIPIV;
}
}
}
if ( n32 !== N ) {
ip = offsetIPIV;
for ( i = 0, k = k1; i < nrows; i++, k += inck ) {
row = IPIV[ ip ];
if ( row !== k ) {
ia1 = offsetA + ( k*strideA1 );
ia2 = offsetA + ( row*strideA1 );
for ( n = n32; n < N; n++ ) {
o = n * strideA2;
tmp = A[ ia1+o ];
A[ ia1+o ] = A[ ia2+o ];
A[ ia2+o ] = tmp;
}
}
ip += strideIPIV;
}
}
return A;
}
// EXPORTS //
module.exports = slaswp;
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