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) 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 isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major-string' );
var resolveOrder = require( '@stdlib/blas/base/layout-resolve-enum' );
var max = require( '@stdlib/math/base/special/fast/max' );
var format = require( '@stdlib/string/format' );
var addon = require( './../src/addon.node' );
// MAIN //
/**
* Reflects the upper triangular part of a double-precision floating-point matrix `A` into the lower triangular part of another matrix `B`.
*
* @param {string} order - storage layout of `A` and `B`
* @param {NonNegativeInteger} M - number of rows in matrix `A`
* @param {NonNegativeInteger} N - number of columns in matrix `A`
* @param {integer} k - diagonal below which to ignore
* @param {Float64Array} A - input matrix
* @param {PositiveInteger} LDA - stride of the first dimension of `A` (a.k.a., leading dimension of the matrix `A`)
* @param {Float64Array} B - output matrix
* @param {PositiveInteger} LDB - stride of the first dimension of `B` (a.k.a., leading dimension of the matrix `B`)
* @throws {TypeError} first argument must be a valid order
* @throws {RangeError} sixth argument must be a valid stride
* @throws {RangeError} eighth argument must be a valid stride
* @returns {Float64Array} `B`
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var A = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
* var B = new Float64Array( [ 0.0, 0.0, 0.0, 0.0 ] );
*
* dtriu2tril( 'row-major', 2, 2, 0, A, 2, B, 2 );
* // B => <Float64Array>[ 1.0, 0.0, 2.0, 4.0 ]
*/
function dtriu2tril( order, M, N, k, A, LDA, B, LDB ) {
var isrm;
var sa;
var sb;
if ( !isLayout( order ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a valid order. Value: `%s`.', order ) );
}
isrm = isRowMajor( order );
if ( isrm ) {
sa = N; // A (M x N) has N columns
sb = M; // B (N x M) has M columns
} else {
sa = M; // A (M x N) has M rows
sb = N; // B (N x M) has N rows
}
if ( LDA < max( 1, sa ) ) {
throw new RangeError( format( 'invalid argument. Sixth argument must be greater than or equal to max(1,%d). Value: `%d`.', sa, LDA ) );
}
if ( LDB < max( 1, sb ) ) {
throw new RangeError( format( 'invalid argument. Eighth argument must be greater than or equal to max(1,%d). Value: `%d`.', sb, LDB ) );
}
addon( resolveOrder( order ), M, N, k, A, LDA, B, LDB );
return B;
}
// EXPORTS //
module.exports = dtriu2tril;
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