|
| 1 | +<!-- |
| 2 | +
|
| 3 | +@license Apache-2.0 |
| 4 | +
|
| 5 | +Copyright (c) 2026 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 | +# zrotg |
| 22 | + |
| 23 | +> Construct a Givens plane rotation. |
| 24 | +
|
| 25 | +<section class="usage"> |
| 26 | + |
| 27 | +## Usage |
| 28 | + |
| 29 | +```javascript |
| 30 | +var zrotg = require( '@stdlib/blas/base/zrotg' ); |
| 31 | +``` |
| 32 | + |
| 33 | +#### zrotg( za, zb ) |
| 34 | + |
| 35 | +Constructs a Givens plane rotation provided two double-precision complex floating-point values `za` and `zb`. |
| 36 | + |
| 37 | +```javascript |
| 38 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 39 | + |
| 40 | +var za = new Complex128( 4.0, 3.0 ); |
| 41 | +var zb = new Complex128( 0.0, 0.0 ); |
| 42 | + |
| 43 | +var out = zrotg( za, zb ); |
| 44 | +// returns <Float64Array>[ 4.0, 3.0, 1.0, 0.0, 0.0 ] |
| 45 | +``` |
| 46 | + |
| 47 | +The function has the following parameters: |
| 48 | + |
| 49 | +- **za**: rotational elimination parameter (complex number). |
| 50 | +- **zb**: rotational elimination parameter (complex number). |
| 51 | + |
| 52 | +The function returns an array with the following elements: |
| 53 | + |
| 54 | +- **r**: real part of the rotated vector (real number). |
| 55 | +- **r_imag**: imaginary part of the rotated vector (real number). |
| 56 | +- **c**: cosine of the rotation angle (real number). |
| 57 | +- **s**: real part of the sine of the rotation angle (real number). |
| 58 | +- **s_imag**: imaginary part of the sine of the rotation angle (real number). |
| 59 | + |
| 60 | +#### zrotg.assign( za, zb, out, stride, offset ) |
| 61 | + |
| 62 | +Constructs a Givens plane rotation provided two double-precision complex floating-point values `za` and `zb` and assigns results to an output array. |
| 63 | + |
| 64 | +```javascript |
| 65 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 66 | +var Float64Array = require( '@stdlib/array/float64' ); |
| 67 | + |
| 68 | +var za = new Complex128( 4.0, 3.0 ); |
| 69 | +var zb = new Complex128( 0.0, 0.0 ); |
| 70 | + |
| 71 | +var out = new Float64Array( 5 ); |
| 72 | + |
| 73 | +var y = zrotg.assign( za, zb, out, 1, 0 ); |
| 74 | +// returns <Float64Array>[ 4.0, 3.0, 1.0, 0.0, 0.0 ] |
| 75 | + |
| 76 | +var bool = ( y === out ); |
| 77 | +// returns true |
| 78 | +``` |
| 79 | + |
| 80 | +</section> |
| 81 | + |
| 82 | +<!-- /.usage --> |
| 83 | + |
| 84 | +<section class="notes"> |
| 85 | + |
| 86 | +## Notes |
| 87 | + |
| 88 | +- `zrotg()` corresponds to the [BLAS][blas] level 1 function [`zrotg`][blas-zrotg]. |
| 89 | + |
| 90 | +</section> |
| 91 | + |
| 92 | +<!-- /.notes --> |
| 93 | + |
| 94 | +<section class="examples"> |
| 95 | + |
| 96 | +## Examples |
| 97 | + |
| 98 | +```javascript |
| 99 | +var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ); |
| 100 | +var Complex128 = require( '@stdlib/complex/float64/ctor' ); |
| 101 | +var zrotg = require( '@stdlib/blas/base/zrotg' ); |
| 102 | + |
| 103 | +var out; |
| 104 | +var i; |
| 105 | + |
| 106 | +function rand() { |
| 107 | + return new Complex128( discreteUniform( -5, 5 ), discreteUniform( -5, 5 ) ); |
| 108 | +} |
| 109 | + |
| 110 | +for ( i = 0; i < 100; i++ ) { |
| 111 | + out = zrotg( rand(), rand() ); |
| 112 | + console.log( out ); |
| 113 | +} |
| 114 | +``` |
| 115 | + |
| 116 | +</section> |
| 117 | + |
| 118 | +<!-- /.examples --> |
| 119 | + |
| 120 | +<!-- C interface documentation. --> |
| 121 | + |
| 122 | +* * * |
| 123 | + |
| 124 | +<section class="c"> |
| 125 | + |
| 126 | +## C APIs |
| 127 | + |
| 128 | +<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. --> |
| 129 | + |
| 130 | +<section class="intro"> |
| 131 | + |
| 132 | +</section> |
| 133 | + |
| 134 | +<!-- /.intro --> |
| 135 | + |
| 136 | +<!-- C usage documentation. --> |
| 137 | + |
| 138 | +<section class="usage"> |
| 139 | + |
| 140 | +### Usage |
| 141 | + |
| 142 | +```c |
| 143 | +#include "stdlib/blas/base/zrotg.h" |
| 144 | +``` |
| 145 | + |
| 146 | +#### c_zrotg( a, b, \*Out, strideOut ) |
| 147 | + |
| 148 | +Constructs a Givens plane rotation provided two double-precision complex floating-point values `a` and `b`. |
| 149 | + |
| 150 | +```c |
| 151 | +#include "stdlib/complex/float64/ctor.h" |
| 152 | + |
| 153 | +double Out[ 5 ]; |
| 154 | +const stdlib_complex128_t a = stdlib_complex128( 4.0, 3.0 ); |
| 155 | +const stdlib_complex128_t b = stdlib_complex128( 0.0, 0.0 ); |
| 156 | + |
| 157 | +c_zrotg( a, b, Out, 1 ); |
| 158 | +// Out => [ 4.0, 3.0, 1.0, 0.0, 0.0 ] |
| 159 | +``` |
| 160 | +
|
| 161 | +The function accepts the following arguments: |
| 162 | +
|
| 163 | +- **a**: `[in] stdlib_complex128_t` rotational elimination parameter. |
| 164 | +- **b**: `[in] stdlib_complex128_t` rotational elimination parameter. |
| 165 | +- **Out**: `[out] double*` output array. |
| 166 | +- **strideOut**: `[in] CBLAS_INT` stride length for `Out`. |
| 167 | +
|
| 168 | +```c |
| 169 | +void c_zrotg( const stdlib_complex128_t a, const stdlib_complex128_t b, double *Out, const CBLAS_INT strideOut ); |
| 170 | +``` |
| 171 | + |
| 172 | +#### c_zrotg_assign( a, b, \*Out, strideOut, offsetOut ) |
| 173 | + |
| 174 | +Constructs a Givens plane rotation provided two double-precision complex floating-point values `a` and `b` using alternative indexing semantics. |
| 175 | + |
| 176 | +```c |
| 177 | +#include "stdlib/complex/float64/ctor.h" |
| 178 | + |
| 179 | +double Out[ 5 ]; |
| 180 | +const stdlib_complex128_t a = stdlib_complex128( 4.0, 3.0 ); |
| 181 | +const stdlib_complex128_t b = stdlib_complex128( 0.0, 0.0 ); |
| 182 | + |
| 183 | +c_zrotg_assign( a, b, Out, 1, 0 ); |
| 184 | +// Out => [ 4.0, 3.0, 1.0, 0.0, 0.0 ] |
| 185 | +``` |
| 186 | +
|
| 187 | +The function accepts the following arguments: |
| 188 | +
|
| 189 | +- **a**: `[in] stdlib_complex128_t` rotational elimination parameter. |
| 190 | +- **b**: `[in] stdlib_complex128_t` rotational elimination parameter. |
| 191 | +- **Out**: `[out] double*` output array. |
| 192 | +- **strideOut**: `[in] CBLAS_INT` stride length for `Out`. |
| 193 | +- **offsetOut**: `[in] CBLAS_INT` starting index for `Out`. |
| 194 | +
|
| 195 | +```c |
| 196 | +void c_zrotg_assign( const stdlib_complex128_t a, const stdlib_complex128_t b, double *Out, const CBLAS_INT strideOut, const CBLAS_INT offsetOut ); |
| 197 | +``` |
| 198 | + |
| 199 | +</section> |
| 200 | + |
| 201 | +<!-- /.usage --> |
| 202 | + |
| 203 | +<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 204 | + |
| 205 | +<section class="notes"> |
| 206 | + |
| 207 | +</section> |
| 208 | + |
| 209 | +<!-- /.notes --> |
| 210 | + |
| 211 | +<!-- C API usage examples. --> |
| 212 | + |
| 213 | +<section class="examples"> |
| 214 | + |
| 215 | +### Examples |
| 216 | + |
| 217 | +```c |
| 218 | +#include "stdlib/blas/base/zrotg.h" |
| 219 | +#include "stdlib/complex/float64/ctor.h" |
| 220 | +#include <stdio.h> |
| 221 | + |
| 222 | +int main( void ) { |
| 223 | + // Specify rotational elimination parameters: |
| 224 | + const stdlib_complex128_t a = stdlib_complex128( 4.0, 3.0 ); |
| 225 | + const stdlib_complex128_t b = stdlib_complex128( 0.0, 0.0 ); |
| 226 | + int i; |
| 227 | + |
| 228 | + // Create output array: |
| 229 | + double Out[ 5 ]; |
| 230 | + |
| 231 | + // Specify stride length: |
| 232 | + const int strideOut = 1; |
| 233 | + |
| 234 | + // Apply plane rotation: |
| 235 | + c_zrotg( a, b, Out, strideOut ); |
| 236 | + |
| 237 | + // Print the result: |
| 238 | + for ( i = 0; i < 5; i++ ) { |
| 239 | + printf( "Out[%d] = %lf\n", i, Out[ i ] ); |
| 240 | + } |
| 241 | + |
| 242 | + // Apply plane rotation using alternative indexing semantics: |
| 243 | + c_zrotg_assign( a, b, Out, strideOut, 0 ); |
| 244 | + |
| 245 | + // Print the result: |
| 246 | + for ( i = 0; i < 5; i++ ) { |
| 247 | + printf( "Out[%d] = %lf\n", i, Out[ i ] ); |
| 248 | + } |
| 249 | +} |
| 250 | +``` |
| 251 | +
|
| 252 | +</section> |
| 253 | +
|
| 254 | +<!-- /.examples --> |
| 255 | +
|
| 256 | +</section> |
| 257 | +
|
| 258 | +<!-- /.c --> |
| 259 | +
|
| 260 | +<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. --> |
| 261 | +
|
| 262 | +<section class="related"> |
| 263 | +
|
| 264 | +</section> |
| 265 | +
|
| 266 | +<!-- /.related --> |
| 267 | +
|
| 268 | +<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 269 | +
|
| 270 | +<section class="links"> |
| 271 | +
|
| 272 | +[blas]: http://www.netlib.org/blas |
| 273 | +
|
| 274 | +[blas-zrotg]: https://www.netlib.org/lapack/explore-html/d7/dc5/group__rotg_ga97ce56a6808661b36ab62269393ac10e.html |
| 275 | +
|
| 276 | +</section> |
| 277 | +
|
| 278 | +<!-- /.links --> |
0 commit comments