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  • lib/node_modules/@stdlib/blas/base/chbmv

‎lib/node_modules/@stdlib/blas/base/chbmv/README.md‎

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<!--
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@license Apache-2.0
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Copyright (c) 2026 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# chbmv
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> Performs the matrix-vector operation `y = α*A*x + β*y` for complex-valued data.
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<section class="usage">
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## Usage
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```javascript
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var chbmv = require( '@stdlib/blas/base/chbmv' );
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```
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#### chbmv( order, uplo, N, K, α, A, LDA, x, sx, β, y, sy )
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Performs the matrix-vector operation `y = α*A*x + β*y`, where `α` and `β` are complex scalars, `x` and `y` are complex vectors, and `A` is an `N` by `N` Hermitian band matrix with `K` sub-diagonals or super-diagonals.
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var A = new Complex64Array( [ 0.0, 0.0, 1.0, 0.0, 2.0, -2.0, 3.0, 0.0, 4.0, -4.0, 5.0, 0.0 ] ); // eslint-disable-line max-params, max-len
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var x = new Complex64Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
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var y = new Complex64Array( [ 3.0, 3.0, 2.0, 2.0, 1.0, 1.0 ] );
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var alpha = new Complex64( 0.5, 0.5 );
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var beta = new Complex64( 0.5, -0.5 );
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chbmv( 'row-major', 'lower', 3, 1, alpha, A, 2, x, 1, beta, y, 1 );
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// y => <Complex64Array>[ -1.0, 5.0, -8.0, 20.0, 9.0, 23.0 ]
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```
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The function has the following parameters:
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- **order**: storage layout.
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- **uplo**: specifies whether the upper or lower triangular part of the matrix `A` is supplied.
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- **N**: specifies number of elements along each dimension of `A`
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- **K**: specifies number of super-diagonals or sub-diagonals of matrix `A`.
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- **α**: complex scalar constant.
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- **A**: complex input matrix stored in linear memory as a [`Complex64Array`][@stdlib/array/complex64].
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- **LDA**: stride of the first dimension of `A` (a.k.a., leading dimension of the matrix `A`).
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- **x**: complex input vector [`Complex64Array`][@stdlib/array/complex64].
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- **sx**: stride length for `x`.
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- **β**: complex scalar constant.
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- **y**: output [`Complex64Array`][@stdlib/array/complex64].
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- **sy**: stride length for `y`.
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The stride parameters determine how elements are accessed. For example, to iterate over every other element in `x` and `y`,
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var A = new Complex64Array( [ 0.0, 0.0, 1.0, 0.0, 2.0, -2.0, 3.0, 0.0, 4.0, -4.0, 5.0, 0.0 ] ); // eslint-disable-line max-params, max-len
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var x = new Complex64Array( [ 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 2.0, 2.0, 0.0, 0.0, 0.0, 0.0, 3.0, 3.0 ] ); // eslint-disable-line max-params, max-len
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var y = new Complex64Array( [ 3.0, 3.0, 0.0, 0.0, 2.0, 2.0, 0.0, 0.0, 1.0, 1.0 ] ); // eslint-disable-line max-params, max-len
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var alpha = new Complex64( 0.5, 0.5 );
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var beta = new Complex64( 0.5, -0.5 );
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chbmv( 'row-major', 'lower', 3, 1, alpha, A, 2, x, 3, beta, y, 2 );
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// y => <Complex64Array>[ -1.0, 5.0, 0.0, 0.0, -8.0, 20.0, 0.0, 0.0, 9.0, 23.0 ]
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```
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Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
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<!-- eslint-disable stdlib/capitalized-comments -->
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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// Initial arrays...
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var x0 = new Complex64Array( [ 0.0, 0.0, 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
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var y0 = new Complex64Array( [ 0.0, 0.0, 3.0, 3.0, 2.0, 2.0, 1.0, 1.0 ] ); // eslint-disable-line max-params, max-len
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var A = new Complex64Array( [ 0.0, 0.0, 1.0, 0.0, 2.0, -2.0, 3.0, 0.0, 4.0, -4.0, 5.0, 0.0 ] ); // eslint-disable-line max-params, max-len
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var alpha = new Complex64( 0.5, 0.5 );
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var beta = new Complex64( 0.5, -0.5 );
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// Create offset views...
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var x1 = new Complex64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd complex element
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var y1 = new Complex64Array( y0.buffer, y0.BYTES_PER_ELEMENT*1 ); // start at 2nd complex element
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chbmv( 'row-major', 'lower', 3, 1, alpha, A, 2, x1, 1, beta, y1, 1 );
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// y1 => <Complex64Array>[ -1.0, 5.0, -8.0, 20.0, 9.0, 23.0 ]
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```
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<!-- lint disable maximum-heading-length -->
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#### chbmv.ndarray( uplo, N, K, α, A, sa1, sa2, oa, x, sx, ox, β, y, sy, oy )
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Performs the matrix-vector operation `y = α*A*x + β*y` using alternative indexing semantics, where `α` and `β` are complex scalars, `x` and `y` are complex vectors, and `A` is an `N` by `N` Hermitian band matrix with `K` sub-diagonals or super-diagonals.
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var A = new Complex64Array( [ 0.0, 0.0, 1.0, 0.0, 2.0, -2.0, 3.0, 0.0, 4.0, -4.0, 5.0, 0.0 ] ); // eslint-disable-line max-params, max-len
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var x = new Complex64Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
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var y = new Complex64Array( [ 3.0, 3.0, 2.0, 2.0, 1.0, 1.0 ] );
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var alpha = new Complex64( 0.5, 0.5 );
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var beta = new Complex64( 0.5, -0.5 );
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chbmv.ndarray( 'lower', 3, 1, alpha, A, 2, 1, 0, x, 1, 0, beta, y, 1, 0 );
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// y => <Complex64Array>[ -1.0, 5.0, -8.0, 20.0, 9.0, 23.0 ]
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```
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The function has the following additional parameters:
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- **sa1**: stride of the first dimension of `A`.
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- **sa2**: stride of the second dimension of `A`.
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- **oa**: starting index for `A`.
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- **ox**: starting index for `x`.
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- **oy**: starting index for `y`.
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While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example,
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var A = new Complex64Array( [ 0.0, 0.0, 1.0, 0.0, 2.0, -2.0, 3.0, 0.0, 4.0, -4.0, 5.0, 0.0 ] ); // eslint-disable-line max-params, max-len
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var x = new Complex64Array( [ 0.0, 0.0, 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
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var y = new Complex64Array( [ 1.0, 1.0, 0.0, 0.0, 2.0, 2.0, 0.0, 0.0, 3.0, 3.0 ] ); // eslint-disable-line max-params, max-len
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var alpha = new Complex64( 0.5, 0.5 );
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var beta = new Complex64( 0.5, -0.5 );
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chbmv.ndarray( 'lower', 3, 1, alpha, A, 1, 2, 0, x, 1, 1, beta, y, -1, 4 );
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// y => <Complex64Array>[ 9.0, 23.0, 0.0, 0.0, -8.0, 20.0, 0.0, 0.0, -1.0, 5.0 ]
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- `chbmv()` corresponds to the [BLAS][blas] level 2 function [`chbmv`][chbmv].
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var filledarrayBy = require( '@stdlib/array/filled-by' );
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var logEach = require( '@stdlib/console/log-each' );
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var chbmv = require( '@stdlib/blas/base/chbmv' );
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function rand() {
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return new Complex64( discreteUniform( 0, 255 ), discreteUniform( -128, 127 ) ); // eslint-disable-line max-params, max-len
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}
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var N = 3;
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var K = 1;
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var A = filledarrayBy( N*(K+1), 'complex64', rand );
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var x = filledarrayBy( N, 'complex64', rand );
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var y = filledarrayBy( N, 'complex64', rand );
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var alpha = new Complex64( 0.5, 0.5 );
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var beta = new Complex64( 0.5, -0.5 );
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chbmv( 'row-major', 'lower', N, 1, alpha, A, (K+1), x, 1, beta, y, 1 );
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// Print the results:
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logEach( '(%s)', x );
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chbmv.ndarray( 'lower', N, 1, alpha, A, (K+1), 1, 0, x, 1, 0, beta, y, 1, 0 );
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// Print the results:
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logEach( '(%s)', x );
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```
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</section>
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<!-- /.examples -->
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<!-- C interface documentation. -->
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* * *
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<section class="c">
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## C APIs
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- C usage documentation. -->
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<section class="usage">
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### Usage
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```c
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TODO
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```
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#### TODO
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TODO.
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```c
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TODO
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```
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TODO
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```c
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TODO
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```
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</section>
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<!-- /.usage -->
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<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- C API usage examples. -->
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<section class="examples">
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### Examples
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```c
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TODO
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```
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</section>
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<!-- /.examples -->
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</section>
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<!-- /.c -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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[blas]: http://www.netlib.org/blas
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[chbmv]: https://www.netlib.org/lapack/explore-html/d7/dda/group__gemv_ga44c85a0d7ecd60a6bc8ca27b222d7792.html#ga44c85a0d7ecd60a6bc8ca27b222d7792
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[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
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[@stdlib/array/complex64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/complex64
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</section>
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<!-- /.links -->

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