Press n or j to go to the next uncovered block, b, p or k for the previous block.
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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.
*/
/* eslint-disable max-len, max-params */
'use strict';
// MODULES //
var leftForwardColumns = require( './left_forward_columns.js' );
var leftBackwardColumns = require( './left_backward_columns.js' );
var leftForwardRows = require( './left_forward_rows.js' );
var leftBackwardRows = require( './left_backward_rows.js' );
var rightForwardColumns = require( './right_forward_columns.js' );
var rightBackwardColumns = require( './right_backward_columns.js' );
var rightForwardRows = require( './right_forward_rows.js' );
var rightBackwardRows = require( './right_backward_rows.js' );
// MAIN //
/**
* Applies a real block reflector `H` or its transpose `H^T` to a real `M` by `N` matrix `C`, from either the left or the right.
*
* ## Notes
*
* - `V` is a double-precision array with dimension `(LDV,K)` if `storev = 'C'`, `(LDV,M)` if `storev = 'R'` and `side = 'L'`, or `(LDV,N)` if `storev = 'R'` and `side = 'R'`.
* - `T` is a double-precision array with dimension `(LDT,K)`. The triangular `K` by `K` matrix `T` in the representation of the block reflector.
* - `C` is a double-precision array with dimension `(LDC,N)`. On entry, the `M` by `N` matrix `C`. On exit, `C` is overwritten by the desired matrix product.
* - `work` is a double-precision array with dimension `(LDWORK,K)`.
*
* @private
* @param {string} side - specifies whether `H` or `H^T` is applied from the left or right
* @param {string} trans - specifies whether to apply `H` or `H^T`
* @param {string} direct - indicates how `H` is formed from a product of elementary reflectors
* @param {string} storev - indicates how the vectors which define the elementary reflectors are stored
* @param {NonNegativeInteger} M - number of rows of the matrix `C`
* @param {NonNegativeInteger} N - number of columns of the matrix `C`
* @param {NonNegativeInteger} K - order of the matrix `T`
* @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 {integer} offsetV - index offset for `V`
* @param {Float64Array} T - input matrix
* @param {integer} strideT1 - stride of the first dimension of `T`
* @param {integer} strideT2 - stride of the second dimension of `T`
* @param {integer} offsetT - index offset for `T`
* @param {Float64Array} C - input matrix
* @param {integer} strideC1 - stride of the first dimension of `C`
* @param {integer} strideC2 - stride of the second dimension of `C`
* @param {integer} offsetC - index offset for `C`
* @param {Float64Array} work - work array
* @param {integer} strideWork1 - stride of the first dimension of `work`
* @param {integer} strideWork2 - stride of the second dimension of `work`
* @param {integer} offsetWork - index offset for `work`
* @returns {Float64Array} updated matrix `C`
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var V = new Float64Array( [ 10.0, 40.0, 70.0, 20.0, 50.0, 80.0, 30.0, 60.0, 90.0 ] );
* var T = new Float64Array( [ 1.0, 0.0, 0.0, 0.0, 2.0, 0.0, 0.0, 0.0, 3.0 ] );
* var C = new Float64Array( [ 11.0, 12.0, 13.0, 21.0, 22.0, 23.0, 31.0, 32.0, 33.0 ] );
* var work = new Float64Array( 9 );
*
* dlarfb( 'left', 'transpose', 'forward', 'columns', 3, 3, 3, V, 3, 1, 0, T, 3, 1, 0, C, 3, 1, 0, work, 3, 1, 0 );
*
* // C => <Float64Array>[ -1350.00, -1400.00, -1450.00, -30961.00, -32102.00, -33243.00, -266612.00, -275464.00, -284316.00 ]
*/
function dlarfb( side, trans, direct, storev, M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork ) {
// Quick return if possible
if ( M <= 0 || N <= 0 ) {
return C;
}
if ( side === 'left' ) {
if ( storev === 'columns' ) {
if ( direct === 'forward' ) {
return leftForwardColumns( M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork, trans );
}
return leftBackwardColumns( M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork, trans );
}
if ( direct === 'forward' ) {
return leftForwardRows( M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork, trans );
}
return leftBackwardRows( M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork, trans );
}
if ( storev === 'columns' ) {
if ( direct === 'forward' ) {
return rightForwardColumns( M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork, trans );
}
return rightBackwardColumns( M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork, trans );
}
if ( direct === 'forward' ) {
return rightForwardRows( M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork, trans );
}
return rightBackwardRows( M, N, K, V, strideV1, strideV2, offsetV, T, strideT1, strideT2, offsetT, C, strideC1, strideC2, offsetC, work, strideWork1, strideWork2, offsetWork, trans );
}
// EXPORTS //
module.exports = dlarfb;
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