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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 isMatrixTriangle = require( '@stdlib/blas/base/assert/is-matrix-triangle' );
var isColumnMajor = require( '@stdlib/ndarray/base/assert/is-column-major-string' );
var max = require( '@stdlib/math/base/special/fast/max' );
var format = require( '@stdlib/string/format' );
var isNorm = require( './is_norm.js' );
var base = require( './base.js' );
// MAIN //
/**
* Computes the value of the one norm, Frobenius norm, infinity norm, or the element of largest absolute value of a real symmetric band matrix `A`.
*
* @param {string} order - storage layout of `AB`
* @param {string} norm - specifies the value to be returned
* @param {string} uplo - specifies whether the upper or lower triangular part of the band matrix `A` is supplied
* @param {NonNegativeInteger} N - order of the matrix `A`
* @param {NonNegativeInteger} K - number of super-/sub-diagonals of the band matrix `A`
* @param {Float64Array} AB - input band matrix stored in banded format
* @param {PositiveInteger} LDAB - stride of the first dimension of `AB` (a.k.a., leading dimension of the matrix `AB`)
* @param {Float64Array} work - workspace array (only referenced when computing the one or infinity norm)
* @throws {TypeError} first argument must be a valid order
* @throws {TypeError} second argument must be a valid norm
* @throws {TypeError} third argument must specify whether to reference the upper or lower triangular matrix
* @throws {RangeError} seventh argument must be a valid stride
* @returns {number} norm value
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var AB = new Float64Array( [ 0.0, 1.0, 2.0, 3.0, 4.0, 5.0 ] );
* var work = new Float64Array( 3 );
*
* var out = dlansb( 'column-major', 'max', 'upper', 3, 1, AB, 2, work );
* // returns 5.0
*/
function dlansb( order, norm, uplo, N, K, AB, LDAB, work ) {
var sa1;
var sa2;
if ( !isLayout( order ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a valid order. Value: `%s`.', order ) );
}
if ( !isNorm( norm ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be a valid norm. Value: `%s`.', norm ) );
}
if ( !isMatrixTriangle( uplo ) ) {
throw new TypeError( format( 'invalid argument. Third argument must specify whether to reference the upper or lower triangular matrix. Value: `%s`.', uplo ) );
}
if ( isColumnMajor( order ) ) {
if ( LDAB < K+1 ) {
throw new RangeError( format( 'invalid argument. Seventh argument must be greater than or equal to %d. Value: `%d`.', K+1, LDAB ) );
}
sa1 = 1;
sa2 = LDAB;
} else { // order === 'row-major'
if ( LDAB < max( 1, N ) ) {
throw new RangeError( format( 'invalid argument. Seventh argument must be greater than or equal to max(1,%d). Value: `%d`.', N, LDAB ) );
}
sa1 = LDAB;
sa2 = 1;
}
return base( norm, uplo, N, K, AB, sa1, sa2, 0, work, 1, 0 );
}
// EXPORTS //
module.exports = dlansb;
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