dppequ.js

/**
* @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 format = require( '@stdlib/string/format' );
var base = require( './base.js' );


// MAIN //

/**
* Computes the row and column scaling factors intended to equilibrate a symmetric positive definite matrix `A` in packed storage and reduce it's condition number (with respect to the two-norm).
*
* @param {string} order - specifies whether `AP` is packed in row-major or column-major order
* @param {string} uplo - 'Upper' or 'Lower' triangle of `A` is stored
* @param {NonNegativeInteger} N - order of the matrix `A`
* @param {Float64Array} AP - array containing the upper or lower triangle of `A` in packed form
* @param {Float64Array} S - array to store the scale factors of `A`
* @param {Float64Array} out - array to store the output
* @throws {TypeError} first argument must be a valid order
* @throws {RangeError} third argument must be a nonnegative integer
* @returns {integer} status code
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var AP = new Float64Array( [ 1.0, 2.0, 3.0, 5.0, 6.0, 9.0 ] );
* var S = new Float64Array( 3 );
* var out = new Float64Array( 2 );
*
* dppequ( 'row-major', 'L', 3, AP, S, out );
* // S => <Float64Array>[ 1, ~0.58, ~0.33 ]
* // out => <Float64Array>[ ~0.33, 9 ]
*/
function dppequ( order, uplo, N, AP, S, out ) {
	if ( !isLayout( order ) ) {
		throw new TypeError( format( 'invalid argument. First argument must be a valid order. Value: `%s`.', order ) );
	}
	if ( N < 0 ) {
		throw new RangeError( format( 'invalid argument. First argument must be a nonnegative integer. Value: `%d`.', N ) );
	}
	return base( order, uplo, N, AP, 1, 0, S, 1, 0, out, 1, 0 );
}


// EXPORTS //

module.exports = dppequ;