|
| 1 | +<!-- |
| 2 | +
|
| 3 | +@license Apache-2.0 |
| 4 | +
|
| 5 | +Copyright (c) 2025 The Stdlib Authors. |
| 6 | +
|
| 7 | +Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | +you may not use this file except in compliance with the License. |
| 9 | +You may obtain a copy of the License at |
| 10 | +
|
| 11 | + http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | +
|
| 13 | +Unless required by applicable law or agreed to in writing, software |
| 14 | +distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | +See the License for the specific language governing permissions and |
| 17 | +limitations under the License. |
| 18 | +
|
| 19 | +--> |
| 20 | + |
| 21 | +# zher2 |
| 22 | + |
| 23 | +> Perform the hermitian rank 1 operation `A = alpha*x*x**H + A`, where `alpha` is a real scalar, `X` is an `N` element vector and `A` is an `N` by `N` hermitian matrix. |
| 24 | +
|
| 25 | +<section class="usage"> |
| 26 | + |
| 27 | +## Usage |
| 28 | + |
| 29 | +```javascript |
| 30 | +var zher2 = require( '@stdlib/blas/base/zher2' ); |
| 31 | +``` |
| 32 | + |
| 33 | +#### zher2( order, uplo, N, α, x, strideX, y, strideY, A, LDA ) |
| 34 | + |
| 35 | +Performs the hermitian rank 1 operation `A = alpha*x*x**H + A`, where `alpha` is a real scalar, `X` is an `N` element vector and `A` is an `N` by `N` hermitian matrix. |
| 36 | + |
| 37 | +```javascript |
| 38 | +var Complex128Array = require( '@stdlib/array/complex128' ); |
| 39 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 40 | + |
| 41 | +var x = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0 ] ); |
| 42 | +var y = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0 ] ); |
| 43 | +var A = new Complex128Array( [ 1.0, 0.0, 0.0, 0.0, 2.0, 3.0, 4.0, 0.0 ] ); |
| 44 | +var alpha = new Complex128( 1.0, 0.0 ); |
| 45 | + |
| 46 | +zher2( 'row-major', 'lower', x.length, alpha, x, 1, y, 1, A, 2 ); |
| 47 | +// A => <Complex128Array>[ 5.0, 0.0, 0.0, 0.0, 6.0, 3.0, 8.0, 0.0 ] |
| 48 | +``` |
| 49 | + |
| 50 | +The function has the following parameters: |
| 51 | + |
| 52 | +- **order**: storage layout. |
| 53 | +- **uplo**: specifies whether the upper or lower triangular part of the matrix `A` is supplied. |
| 54 | +- **N**: specifies the order of the matrix `A`. |
| 55 | +- **α**: scalar constant. |
| 56 | +- **x**: first input vector [`Complex128Array`][@stdlib/array/complex128]. |
| 57 | +- **strideX**: index increment for `x`. |
| 58 | +- **y**: second input vector [`Complex128Array`][@stdlib/array/complex128]. |
| 59 | +- **strideY**: index increment for `y`. |
| 60 | +- **A**: input matrix stored in linear memory as [`Complex128Array`][@stdlib/array/complex128]. |
| 61 | +- **LDA**: stride of the first dimension of `A` (a.k.a., leading dimension of the matrix `A`). |
| 62 | + |
| 63 | +The stride parameters determine how elements in the input arrays are accessed at runtime. For example, to iterate over the elements of `x` in reverse order, |
| 64 | + |
| 65 | +```javascript |
| 66 | +var Complex128Array = require( '@stdlib/array/complex128' ); |
| 67 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 68 | + |
| 69 | +var x = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0 ] ); |
| 70 | +var y = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0 ] ); |
| 71 | +var A = new Complex128Array( [ 1.0, 0.0, 0.0, 0.0, 2.0, 3.0, 4.0, 0.0 ] ); |
| 72 | +var alpha = new Complex128( 1.0, 0.0 ); |
| 73 | + |
| 74 | +zher2( 'row-major', 'lower', x.length, alpha, x, 1, y, 1, A, 2 ); |
| 75 | +// A => <Complex128Array>[ 5.0, 0.0, 0.0, 0.0, 6.0, 3.0, 8.0, 0.0 ] |
| 76 | +``` |
| 77 | + |
| 78 | +Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views. |
| 79 | + |
| 80 | +<!-- eslint-disable stdlib/capitalized-comments --> |
| 81 | + |
| 82 | +```javascript |
| 83 | +var Complex128Array = require( '@stdlib/array/complex128' ); |
| 84 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 85 | + |
| 86 | +// Initial array: |
| 87 | +var x0 = new Complex128Array( [ 0.0, 0.0, 1.0, 1.0, 1.0, 1.0 ] ); |
| 88 | +var y0 = new Complex128Array( [ 0.0, 0.0, 1.0, 1.0, 1.0, 1.0 ] ); |
| 89 | + |
| 90 | +var alpha = new Complex128( 1.0, 0.0 ); |
| 91 | + |
| 92 | +// Define a input matrix: |
| 93 | +var A = new Complex128Array( [ 1.0, 0.0, 0.0, 0.0, 2.0, 3.0, 4.0, 0.0 ] ); |
| 94 | + |
| 95 | +// Create an offset view: |
| 96 | +var x1 = new Complex128Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element |
| 97 | +var y1 = new Complex128Array( y0.buffer, y0.BYTES_PER_ELEMENT*1 ); // start at 2nd element |
| 98 | + |
| 99 | +zher2( 'row-major', 'lower', x1.length, alpha, x1, 1, y1, 1, A, 2 ); |
| 100 | +// A => <Complex128Array>[ 5.0, 0.0, 0.0, 0.0, 6.0, 3.0, 8.0, 0.0 ] |
| 101 | +``` |
| 102 | + |
| 103 | +<!-- lint disable maximum-heading-length --> |
| 104 | + |
| 105 | +#### zher2.ndarray( uplo, N, α, x, strideX, offsetX, y, strideY, offsetY, A, strideA1, strideA2, offsetA ) |
| 106 | + |
| 107 | +Performs the hermitian rank 1 operation `A = alpha*x*x**H + A`, where `alpha` is a real scalar, `X` is an `N` element vector and `A` is an `N` by `N` hermitian matrix using alternative indexing semantics. |
| 108 | + |
| 109 | +```javascript |
| 110 | +var Complex128Array = require( '@stdlib/array/complex128' ); |
| 111 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 112 | + |
| 113 | +var x = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0 ] ); |
| 114 | +var y = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0 ] ); |
| 115 | +var A = new Complex128Array( [ 1.0, 0.0, 0.0, 0.0, 2.0, 3.0, 4.0, 0.0 ] ); |
| 116 | +var alpha = new Complex128( 1.0, 0.0 ); |
| 117 | + |
| 118 | +zher2.ndarray( 'lower', x.length, alpha, x, 1, 0, y, 1, 0, A, 2, 1, 0 ); |
| 119 | +// A => <Complex128Array>[ 5.0, 0.0, 0.0, 0.0, 6.0, 3.0, 8.0, 0.0 ] |
| 120 | +``` |
| 121 | + |
| 122 | +The function has the following additional parameters: |
| 123 | + |
| 124 | +- **strideA1**: stride of the first dimension of `A`. |
| 125 | +- **strideA2**: stride of the second dimension of `A`. |
| 126 | +- **offsetX**: starting index for `x`. |
| 127 | +- **offsetY**: starting index for `y`. |
| 128 | +- **offsetA**: starting index for `A`. |
| 129 | + |
| 130 | +While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to scale every other value in the input strided array starting from the second element, |
| 131 | + |
| 132 | +```javascript |
| 133 | +var Complex128Array = require( '@stdlib/array/complex128' ); |
| 134 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 135 | + |
| 136 | +var x = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0 ] ); |
| 137 | +var y = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0 ] ); |
| 138 | +var A = new Complex128Array( [ 1.0, 0.0, 0.0, 0.0, 2.0, 3.0, 4.0, 0.0 ] ); |
| 139 | +var alpha = new Complex128( 1.0, 0.0 ); |
| 140 | + |
| 141 | +zher2.ndarray( 'lower', x.length, alpha, x, -1, 0, y, -1, 0, A, 2, 1, 0 ); |
| 142 | +// A => <Complex128Array>[ 5.0, 0.0, 0.0, 0.0, 6.0, 3.0, 8.0, 0.0 ] |
| 143 | +``` |
| 144 | + |
| 145 | +</section> |
| 146 | + |
| 147 | +<!-- /.usage --> |
| 148 | + |
| 149 | +<section class="notes"> |
| 150 | + |
| 151 | +## Notes |
| 152 | + |
| 153 | +- If `N = 0` or `real( α ) = 0.0` or `imag( α ) = 0.0`, both functions return `x` unchanged. |
| 154 | +- `zher2()` corresponds to the [BLAS][blas] level 2 function [`zher2`][zher2]. |
| 155 | + |
| 156 | +</section> |
| 157 | + |
| 158 | +<!-- /.notes --> |
| 159 | + |
| 160 | +<section class="examples"> |
| 161 | + |
| 162 | +## Examples |
| 163 | + |
| 164 | +<!-- eslint no-undef: "error" --> |
| 165 | + |
| 166 | +```javascript |
| 167 | +var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ); |
| 168 | +var filledarrayBy = require( '@stdlib/array/filled-by' ); |
| 169 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 170 | +var logEach = require( '@stdlib/console/log-each' ); |
| 171 | +var zher2 = require( '@stdlib/blas/base/zher2' ); |
| 172 | + |
| 173 | +function rand() { |
| 174 | + return new Complex128( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) ); |
| 175 | +} |
| 176 | + |
| 177 | +var x = filledarrayBy( 3, 'complex128', rand ); |
| 178 | +console.log( x.get( 0 ).toString() ); |
| 179 | + |
| 180 | +var y = filledarrayBy( 3, 'complex128', rand ); |
| 181 | +console.log( y.get( 0 ).toString() ); |
| 182 | + |
| 183 | +var A = filledarrayBy( 9, 'complex128', rand ); |
| 184 | +console.log( A.get( 0 ).toString() ); |
| 185 | + |
| 186 | +var alpha = new Complex128( 2.0, 2.0 ); |
| 187 | +console.log( alpha.toString() ); |
| 188 | + |
| 189 | +zher2( 'row-major', 'upper', 3, alpha, x, 1, y, 1, A, 3 ); |
| 190 | + |
| 191 | +// Print the results: |
| 192 | +logEach( '(%s)', A ); |
| 193 | + |
| 194 | +zher2.ndarray( 'upper', 3, alpha, x, 1, 0, y, 1, 0, A, 3, 1, 0 ); |
| 195 | + |
| 196 | +// Print the results: |
| 197 | +logEach( '(%s)', A ); |
| 198 | +``` |
| 199 | + |
| 200 | +</section> |
| 201 | + |
| 202 | +<!-- /.examples --> |
| 203 | + |
| 204 | +<!-- C interface documentation. --> |
| 205 | + |
| 206 | +* * * |
| 207 | + |
| 208 | +<section class="c"> |
| 209 | + |
| 210 | +## C APIs |
| 211 | + |
| 212 | +<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. --> |
| 213 | + |
| 214 | +<section class="intro"> |
| 215 | + |
| 216 | +</section> |
| 217 | + |
| 218 | +<!-- /.intro --> |
| 219 | + |
| 220 | +<!-- C usage documentation. --> |
| 221 | + |
| 222 | +<section class="usage"> |
| 223 | + |
| 224 | +### Usage |
| 225 | + |
| 226 | +```c |
| 227 | +TODO |
| 228 | +``` |
| 229 | + |
| 230 | +#### TODO |
| 231 | + |
| 232 | +TODO. |
| 233 | + |
| 234 | +```c |
| 235 | +TODO |
| 236 | +``` |
| 237 | + |
| 238 | +TODO |
| 239 | + |
| 240 | +```c |
| 241 | +TODO |
| 242 | +``` |
| 243 | + |
| 244 | +</section> |
| 245 | + |
| 246 | +<!-- /.usage --> |
| 247 | + |
| 248 | +<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 249 | + |
| 250 | +<section class="notes"> |
| 251 | + |
| 252 | +</section> |
| 253 | + |
| 254 | +<!-- /.notes --> |
| 255 | + |
| 256 | +<!-- C API usage examples. --> |
| 257 | + |
| 258 | +<section class="examples"> |
| 259 | + |
| 260 | +### Examples |
| 261 | + |
| 262 | +```c |
| 263 | +TODO |
| 264 | +``` |
| 265 | + |
| 266 | +</section> |
| 267 | + |
| 268 | +<!-- /.examples --> |
| 269 | + |
| 270 | +</section> |
| 271 | + |
| 272 | +<!-- /.c --> |
| 273 | + |
| 274 | +<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. --> |
| 275 | + |
| 276 | +<section class="related"> |
| 277 | + |
| 278 | +</section> |
| 279 | + |
| 280 | +<!-- /.related --> |
| 281 | + |
| 282 | +<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 283 | + |
| 284 | +<section class="links"> |
| 285 | + |
| 286 | +[blas]: http://www.netlib.org/blas |
| 287 | + |
| 288 | +[zher2]: https://www.netlib.org/lapack/explore-html/dd/de5/group__her2_gaf421f493e6422d08e3acfc6d33bfbf46.html |
| 289 | + |
| 290 | +[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray |
| 291 | + |
| 292 | +[@stdlib/array/complex128]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/complex128 |
| 293 | + |
| 294 | +</section> |
| 295 | + |
| 296 | +<!-- /.links --> |
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