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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 isLayout = require( '@stdlib/blas/base/assert/is-layout' );
var format = require( '@stdlib/string/format' );
var isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major-string' );
var max = require( '@stdlib/math/base/special/fast/max' );
var base = require( './base.js' );
// MAIN //
/**
* Compute a QR factorization of a real M-by-N matrix `A`.
*
* ## Notes
*
* - On exit, the elements on and above the diagonal of the array contain the `min(M,N)-by-N` upper trapezoidal matrix `R` (`R` is upper triangular if `m >= n`).
* - On exit, the elements below the diagonal, with the array `TAU`, represent the orthogonal matrix `Q` as a product of `min(m,n)` elementary reflectors.
* - `LWORK >= 1`, if `MIN(M,N) = 0`, and `LWORK >= N`, otherwise. For optimum performance `LWORK >= N*NB`, where `NB` is the optimal blocksize.
* - If `LWORK = -1`, then a workspace query is assumed; the routine only calculates the optimal size of the `WORK` array, returns this value as the first entry of the `WORK` array
*
* @param {string} order - storage layout
* @param {NonNegativeInteger} M - number of rows in `A`
* @param {NonNegativeInteger} N - number of columns in `A`
* @param {Float64Array} A - input/output matrix
* @param {integer} LDA - stride of the first dimension of `A` (a.k.a., leading dimension of the matrix `A`)
* @param {Float64Array} TAU - output array of scalar factors (length `min(M,N)`)
* @param {Float64Array} WORK - workspace array (length >= `M`)
* @param {NonNegativeInteger} LWORK - dimension of the array `WORK`
* @throws {TypeError} first argument must be a valid order
* @throws {RangeError} second argument must be a non-negative integer
* @throws {RangeError} third argument must be a non-negative integer
* @throws {RangeError} fifth argument must be a valid `LDA` value
* @throws {RangeError} eight argument must be a valid `LWORK` value
* @returns {integer} status code (0 if successful)
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var A = new Float64Array( [ 1, 5, 9, 2, 6, 10, 3, 7, 11, 4, 8, 12 ] );
* var TAU = new Float64Array( 3 );
* var WORK = new Float64Array( 4 );
*
* dgeqrf( 'column-major', 3, 4, A, 3, TAU, WORK, 4 );
* // A => <Float64Array>[ ~-10.344, ~0.441, ~0.793, ~-11.794, ~0.947, ~0.919, ~-13.244, ~1.894, ~0.0, ~-14.694, ~2.842, ~0.0 ]
* // TAU => <Float64Array>[ ~1.097, ~1.084, 0.0 ]
* // WORK => <Float64Array>[ 4.0, ~-2.842, ~17.046, 0.0 ]
*/
function dgeqrf( order, M, N, A, LDA, TAU, WORK, LWORK ) { // eslint-disable-line stdlib/jsdoc-doctest-decimal-point
var sa1;
var sa2;
if ( !isLayout( order ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a valid order. Value: `%s`.', order ) );
}
if ( M < 0 ) {
throw new RangeError( format( 'invalid argument. Second argument must be a nonnegative integer. Value: `%d`.', M ) );
}
if ( N < 0 ) {
throw new RangeError( format( 'invalid argument. Third argument must be a nonnegative integer. Value: `%d`.', N ) );
}
if ( isRowMajor( order ) ) {
if ( LDA < max( 1, N ) ) {
throw new RangeError( format( 'invalid argument. Fifth argument must be greater than or equal to `max(1,N)`. Value: `%d`.', LDA ) );
}
} else if ( LDA < max( 1, M ) ) {
throw new RangeError( format( 'invalid argument. Fifth argument must be greater than or equal to `max(1,M)`. Value: `%d`.', LDA ) );
}
if ( LWORK !== -1 && ( LWORK <= 0 || ( M > 0 && LWORK < max( 1, N ) ) ) ) {
throw new RangeError( format( 'invalid argument. Eighth argument must be a valid LWORK value. Value: `%d`.', LWORK ) );
}
if ( order === 'column-major' ) {
sa1 = 1;
sa2 = LDA;
} else {
sa1 = LDA;
sa2 = 1;
}
return base( M, N, A, sa1, sa2, 0, TAU, 1, 0, WORK, 1, 0, LWORK );
}
// EXPORTS //
module.exports = dgeqrf;
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