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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 isMatrixTriangle = require( '@stdlib/blas/base/assert/is-matrix-triangle' );
var base = require( './base.js' );
// MAIN //
/**
* Performs the matrix-vector operation `y = alpha*A*x + beta*y` where `alpha` and `beta` are scalars, `x` and `y` are `N` element vectors, and `A` is an `N` by `N` symmetric band matrix, with `K` super-diagonals.
*
* @param {string} uplo - specifies whether the upper or lower triangular part of the symmetric matrix `A` should be referenced
* @param {NonNegativeInteger} N - number of elements along each dimension of `A`
* @param {NonNegativeInteger} K - number of super-diagonals of the matrix `A`
* @param {number} alpha - scalar constant
* @param {Float32Array} A - matrix
* @param {integer} strideA1 - stride of the first dimension of `A`
* @param {integer} strideA2 - stride of the second dimension of `A`
* @param {NonNegativeInteger} offsetA - starting index for `A`
* @param {Float32Array} x - first input array
* @param {integer} strideX - `x` stride length
* @param {NonNegativeInteger} offsetX - starting `x` index
* @param {number} beta - scalar constant
* @param {Float32Array} y - second input array
* @param {integer} strideY - `y` stride length
* @param {NonNegativeInteger} offsetY - starting `y` index
* @throws {TypeError} first argument must specify whether to reference the lower or upper triangular matrix
* @throws {RangeError} second argument must be a nonnegative integer
* @throws {RangeError} third argument must be a nonnegative integer
* @throws {RangeError} sixth argument must be greater than or equal to max(1,N)
* @throws {RangeError} eighth argument must be non-zero
* @throws {RangeError} twelfth argument must be non-zero
* @returns {Float32Array} `y`
*
* @example
* var Float32Array = require( '@stdlib/array/float32' );
*
* var A = new Float32Array( [ 1.0, 2.0, 4.0, 3.0, 5.0, 0.0 ] );
* var x = new Float32Array( [ 1.0, 2.0, 3.0 ] );
* var y = new Float32Array( [ 0.0, 0.0, 0.0 ] );
*
* ssbmv( 'lower', 3, 1, 1.0, A, 2, 1, 0, x, 1, 0, 0.0, y, 1, 0 );
* // y => <Float32Array>[ 10.0, 25.0, 10.0 ]
*/
function ssbmv( uplo, N, K, alpha, A, strideA1, strideA2, offsetA, x, strideX, offsetX, beta, y, strideY, offsetY ) { // eslint-disable-line max-params, max-len
if ( !isMatrixTriangle( uplo ) ) {
throw new TypeError( 'invalid argument. First argument must specify whether to reference the lower or upper triangular matrix. Value: `%s`.', uplo );
}
if ( N < 0 ) {
throw new RangeError( 'invalid argument. Second argument must be a nonnegative integer. Value: `%d`.', N );
}
if ( K < 0 ) {
throw new RangeError( 'invalid argument. Third argument must be a nonnegative integer. Value: `%d`.', K );
}
if ( strideA1 === 0 ) {
throw new RangeError( 'invalid argument. Sixth argument must be non-zero. Value: `%d`.', strideX );
}
if ( strideA2 === 0 ) {
throw new RangeError( 'invalid argument. Seventh argument must be non-zero. Value: `%d`.', strideX );
}
if ( strideX === 0 ) {
throw new RangeError( 'invalid argument. Tenth argument must be non-zero. Value: `%d`.', strideX );
}
if ( strideY === 0 ) {
throw new RangeError( 'invalid argument. Fourteenth argument must be non-zero. Value: `%d`.', strideY );
}
// Check if we can early return...
if ( N === 0 || ( alpha === 0.0 && beta === 1.0 ) ) {
return y;
}
return base( uplo, N, K, alpha, A, strideA1, strideA2, offsetA, x, strideX, offsetX, beta, y, strideY, offsetY ); // eslint-disable-line max-len
}
// EXPORTS //
module.exports = ssbmv;
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