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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 isLayout = require( '@stdlib/blas/base/assert/is-layout' );
var isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major-string' );
var isColumnMajor = require( '@stdlib/ndarray/base/assert/is-column-major-string' );
var max = require( '@stdlib/math/base/special/max' );
var format = require( '@stdlib/string/format' );
var stride2offset = require( '@stdlib/strided/base/stride2offset' );
var base = require( './base.js' );
// MAIN //
/**
* Applies a real elementary reflector `H = I - tau * v * v ^ T` to a real M by N matrix `C`.
*
* ## Notes
*
* - `work` should have `N` indexed elements if side = `left` and `M` indexed elements if side = `right`.
* - `V` should have `1 + (M-1) * abs(incv)` indexed elements if side = `left` and `1 + (N-1) * abs(incv)` indexed elements if side = `right`.
* - `C` is overwritten by `H * C` if side = `left` and `C * H` if side = `right`.
*
* @param {string} order - storage layout
* @param {string} side - use `left` to form `H * C` and `right` to from `C * H`
* @param {NonNegativeInteger} M - number of rows in `C`
* @param {NonNegativeInteger} N - number of columns in `C`
* @param {Float64Array} V - the vector `v` in the representation of `H`
* @param {integer} incv - stride length for `V`
* @param {number} tau - the value of `tau` in representation of `H`
* @param {Float64Array} C - input matrix
* @param {PositiveInteger} LDC - stride of the first dimension of `C` (a.k.a., leading dimension of the matrix `C`)
* @param {Float64Array} work - workspace array
* @throws {TypeError} first argument must be a valid order
* @throws {TypeError} second argument must be a valid side
* @throws {RangeError} ninth argument must be greater than or equal to max(1,N)
* @throws {RangeError} fifth argument must not be zero
* @returns {Float64Array} `C * H` or `H * C`
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var C = new Float64Array( [ 1.0, 5.0, 9.0, 2.0, 6.0, 10.0, 3.0, 7.0, 11.0, 4.0, 8.0, 12.0 ] );
* var V = new Float64Array( [ 0.5, 0.5, 0.5, 0.5 ] );
* var work = new Float64Array( 3 );
*
* var out = dlarf1f( 'row-major', 'left', 4, 3, V, 1, 1.0, C, 3, work );
* // returns <Float64Array>[ -4.5, -10.5, -16.5, -0.75, -1.75, -2.75, 0.25, -0.75, -1.75, 1.25, 0.25, -0.75 ]
*/
function dlarf1f( order, side, M, N, V, incv, tau, C, LDC, work ) {
var sc1;
var sc2;
var ov;
if ( !isLayout( order ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a valid order. Value: `%s`.', order ) );
}
if ( isRowMajor( order ) && LDC < max( 1, N ) ) {
throw new RangeError( format( 'invalid argument. Fourth argument must be greater than or equal to max(1,%d). Value: `%d`.', N, LDC ) );
}
if ( side !== 'left' && side !== 'right' ) { // TODO - refactor this to make use of an array if needed
throw new TypeError( format( 'invalid argument. Second argument must be a valid side (left or right). Value: `%s`.', side ) );
}
if ( incv === 0 ) {
throw new RangeError( format( 'invalid argument. Fifth argument must not be zero' ) );
}
if ( isColumnMajor( order ) ) {
sc1 = 1;
sc2 = LDC;
} else { // order === 'row-major'
sc1 = LDC;
sc2 = 1;
}
if ( side === 'left' ) {
ov = stride2offset( M, incv );
} else {
ov = stride2offset( N, incv );
}
return base( side, M, N, V, incv, ov, tau, C, sc1, sc2, 0, work, 1, 0 );
}
// EXPORTS //
module.exports = dlarf1f;
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