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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 isColumnMajor = require( '@stdlib/ndarray/base/assert/is-column-major-string' );
var format = require( '@stdlib/string/format' );
var isJob = require( './isjob.js' );
var base = require( './base.js' );
// MAIN //
/**
* Balances a general real matrix `A`.
*
* ## Notes
*
* The job parameter can be one of the following:
*
* - 'none': none, return immediately
* - 'permute': permute only
* - 'scale': scale only
* - 'both': both permute and scale
*
* The matrix `A` is overwritten by the balanced matrix. Scale factors are stored in the `scale` array. If `P[ j ]` is the index of the row and column interchanged with row and column j (zero-based) and `D[ j ]` is the scaling factor applied to row and column j, then:
*
* - `scale[ j ]` = `P[ j ]` for j = `0`,...,`out[ 0 ]-1`
* - `scale[ j ]` = `D[ j ]` for j = `out[ 0 ]`,...,`out[ 1 ]`
* - `scale[ j ]` = `P[ j ]` for j = `out[ 1 ]+1`,...,`N-1`.
*
* The order in which the interchanges are made is `N-1` to `out[ 1 ]+1`, then `0` to `out[ 0 ]-1`.
*
* @private
* @param {string} order - storage layout of `A`
* @param {string} job - indicates the operations to be performed
* @param {NonNegativeInteger} N - number of rows/columns in matrix `A`
* @param {Float64Array} A - input matrix to be balanced
* @param {NonNegativeInteger} LDA - leading dimension of `A`
* @param {Int32Array} out - stores the first and last row/column of the balanced submatrix
* @param {Float64Array} scale - array containing permutation and scaling information
* @throws {TypeError} first argument must be a valid order
* @throws {TypeError} second argument must be a valid job
* @throws {RangeError} fifth argument must be greater than or equal to `N`
* @returns {integer} status code
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
* var Int32Array = require( '@stdlib/array/int32' );
*
* var A = new Float64Array( [ 1.0, 100.0, 0.0, 2.0, 200.0, 0.0, 0.0, 0.0, 3.0 ] );
* var out = new Int32Array( 2 );
* var scale = new Float64Array( 3 );
*
* dgebal( 'row-major', 'both', 3, A, 3, out, scale );
* // A => <Float64Array>[ 1, 12.5, 0, 16, 200, 0, 0, 0, 3 ]
* // out => <Int32Array>[ 0, 1 ]
* // scale => <Float64Array>[ 8, 1, 2 ]
*/
function dgebal( order, job, N, A, LDA, out, scale ) {
var sa1;
var sa2;
if ( !isLayout( order ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a valid order. Value: `%s`.', order ) );
}
if ( !isJob( job ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be one of the following: `both`, `scale`, `permute`, or `none`. Value: `%s`.', job ) );
}
if ( isColumnMajor( order ) ) {
sa1 = 1;
sa2 = LDA;
} else { // order === 'row-major'
if ( LDA < N ) {
throw new RangeError( format( 'invalid argument. Fifth argument must be greater than or equal to %d. Value: `%d`.', N, LDA ) );
}
sa1 = LDA;
sa2 = 1;
}
return base( job, N, A, sa1, sa2, 0, out, 1, 0, scale, 1, 0 );
}
// EXPORTS //
module.exports = dgebal;
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