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| 1 | +<!-- |
| 2 | +
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| 3 | +@license Apache-2.0 |
| 4 | +
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| 5 | +Copyright (c) 2024 The Stdlib Authors. |
| 6 | +
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| 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 | +
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| 11 | + http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | +
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| 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 | +# dlassq |
| 22 | + |
| 23 | +> Return an updated sum of squares represented in scaled form. |
| 24 | +
|
| 25 | +<section class="intro"> |
| 26 | + |
| 27 | +This routine returns the values $s_{textrm{out}}$ and $\textrm{ss}_{\textrm{out}}$ such that |
| 28 | + |
| 29 | +<!-- <equation class="equation" label="eq:sum_of_squares" align="center" raw="s_{\textrm{out}}^2 \cdot \textrm{ss}_{\textrm{out}} = x_0^2 + \ldots + x_{N-1}^2 + s_{\textrm{in}}^2 \cdot \textrm{ss}_{\textrm{in}}" alt="Sum of squares represented in scaled form"> --> |
| 30 | + |
| 31 | +<div class="equation" align="center" data-raw-text="s_{\textrm{out}}^2 \cdot \textrm{ss}_{\textrm{out}} = x_0^2 + \ldots + x_{N-1}^2 + s_{\textrm{in}}^2 \cdot \textrm{ss}_{\textrm{in}}" data-equation="eq:sum_of_squares"> |
| 32 | + <img src="" alt="Sum of squares represented in scaled form"> |
| 33 | + <br> |
| 34 | +</div> |
| 35 | + |
| 36 | +<!-- </equation> --> |
| 37 | + |
| 38 | +where $x_i = X_{(i-1) \cdot \textrm{sx}}$ and $\textrm{sx}$ is the stride of `X`. The value of $\textrm{ss}_{\textrm{in}}$ is assumed to be nonnegative. |
| 39 | + |
| 40 | +</section> |
| 41 | + |
| 42 | +<!-- /.intro --> |
| 43 | + |
| 44 | +<section class="usage"> |
| 45 | + |
| 46 | +## Usage |
| 47 | + |
| 48 | +```javascript |
| 49 | +var dlassq = require( '@stdlib/lapack/base/dlassq' ); |
| 50 | +``` |
| 51 | + |
| 52 | +#### dlassq( N, X, strideX, scale, sumsq ) |
| 53 | + |
| 54 | +Returns an updated sum of squares represented in scaled form. |
| 55 | + |
| 56 | +```javascript |
| 57 | +var Float64Array = require( '@stdlib/array/float64' ); |
| 58 | + |
| 59 | +var X = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] ); |
| 60 | + |
| 61 | +var out = dlassq( 4, X, 1, 1.0, 0.0 ); |
| 62 | +// returns <Float64Array>[ 1.0, 30.0 ] |
| 63 | +``` |
| 64 | + |
| 65 | +The function has the following parameters: |
| 66 | + |
| 67 | +- **N**: number of indexed elements. |
| 68 | +- **X**: input [`Float64Array`][mdn-float64array]. |
| 69 | +- **strideX**: stride length for `X`. |
| 70 | +- **scale**: scaling factor. |
| 71 | +- **sumsq**: basic sum of squares from which output is factored out. |
| 72 | + |
| 73 | +Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views. |
| 74 | + |
| 75 | +<!-- eslint-disable stdlib/capitalized-comments --> |
| 76 | + |
| 77 | +```javascript |
| 78 | +var Float64Array = require( '@stdlib/array/float64' ); |
| 79 | + |
| 80 | +// Initial array: |
| 81 | +var X0 = new Float64Array( [ 0.0, 1.0, 2.0, 3.0, 4.0 ] ); |
| 82 | + |
| 83 | +// Create an offset view: |
| 84 | +var X1 = new Float64Array( X0.buffer, X0.BYTES_PER_ELEMENT*1 ); // start at 2nd element |
| 85 | + |
| 86 | +// Compute the sum of squares: |
| 87 | +var out = dlassq( X1.length, X1, 1, 1.0, 0.0 ); |
| 88 | +// returns <Float64Array>[ 1.0, 30.0 ] |
| 89 | +``` |
| 90 | + |
| 91 | +The returned [`Float64Array`][mdn-float64array] contains an updated scale factor and an updated sum of squares, respectively. |
| 92 | + |
| 93 | +#### dlassq.ndarray( N, X, sx, ox, scale, sumsq, out, so, oo ) |
| 94 | + |
| 95 | +Returns an updated sum of squares represented in scaled form using alternative indexing semantics. |
| 96 | + |
| 97 | +```javascript |
| 98 | +var Float64Array = require( '@stdlib/array/float64' ); |
| 99 | + |
| 100 | +var X = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] ); |
| 101 | +var out = new Float64Array( [ 0.0, 0.0 ] ); |
| 102 | + |
| 103 | +dlassq.ndarray( 4, X, 1, 0, 1.0, 0.0, out, 1, 0 ); |
| 104 | +// out => <Float64Array>[ 1.0, 30.0 ] |
| 105 | +``` |
| 106 | + |
| 107 | +The function has the following additional parameters: |
| 108 | + |
| 109 | +- **ox**: starting index for `X`. |
| 110 | +- **out**: output [`Float64Array`][mdn-float64array] |
| 111 | +- **so**: stride length for `out`. |
| 112 | +- **oo**: starting index for `out`. |
| 113 | + |
| 114 | +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, |
| 115 | + |
| 116 | +<!-- eslint-disable max-len --> |
| 117 | + |
| 118 | +```javascript |
| 119 | +var Float64Array = require( '@stdlib/array/float64' ); |
| 120 | + |
| 121 | +var X = new Float64Array( [ 1.0, 0.0, 2.0, 0.0, 3.0, 0.0, 4.0 ] ); |
| 122 | +var out = new Float64Array( [ 0.0, 0.0, 999.9, 0.0, 999.9 ] ); |
| 123 | + |
| 124 | +dlassq.ndarray( 4, X, 2, 0, 1.0, 0.0, out, 2, 1 ); |
| 125 | +// out => <Float64Array>[ 0.0, 1.0, 999.9, 30.0, 999.9 ] |
| 126 | +``` |
| 127 | + |
| 128 | +</section> |
| 129 | + |
| 130 | +<!-- /.usage --> |
| 131 | + |
| 132 | +<section class="notes"> |
| 133 | + |
| 134 | +## Notes |
| 135 | + |
| 136 | +- `dlassq()` corresponds to the [LAPACK][LAPACK] function [`dlassq`][lapack-dlassq]. |
| 137 | + |
| 138 | +</section> |
| 139 | + |
| 140 | +<!-- /.notes --> |
| 141 | + |
| 142 | +<section class="examples"> |
| 143 | + |
| 144 | +## Examples |
| 145 | + |
| 146 | +<!-- eslint no-undef: "error" --> |
| 147 | + |
| 148 | +```javascript |
| 149 | +var discreteUniform = require( '@stdlib/random/array/discrete-uniform' ); |
| 150 | +var dlassq = require( '@stdlib/lapack/base/dlassq' ); |
| 151 | + |
| 152 | +var X = discreteUniform( 10, -10, 10, { |
| 153 | + 'dtype': 'float64' |
| 154 | +}); |
| 155 | +console.log( X ); |
| 156 | + |
| 157 | +var out = dlassq( X.length, X, 1, 1.0, 0.0 ); |
| 158 | +console.log( out ); |
| 159 | +``` |
| 160 | + |
| 161 | +</section> |
| 162 | + |
| 163 | +<!-- /.examples --> |
| 164 | + |
| 165 | +<!-- C interface documentation. --> |
| 166 | + |
| 167 | +* * * |
| 168 | + |
| 169 | +<section class="c"> |
| 170 | + |
| 171 | +## C APIs |
| 172 | + |
| 173 | +<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. --> |
| 174 | + |
| 175 | +<section class="intro"> |
| 176 | + |
| 177 | +</section> |
| 178 | + |
| 179 | +<!-- /.intro --> |
| 180 | + |
| 181 | +<!-- C usage documentation. --> |
| 182 | + |
| 183 | +<section class="usage"> |
| 184 | + |
| 185 | +### Usage |
| 186 | + |
| 187 | +```c |
| 188 | +TODO |
| 189 | +``` |
| 190 | + |
| 191 | +#### TODO |
| 192 | + |
| 193 | +TODO. |
| 194 | + |
| 195 | +```c |
| 196 | +TODO |
| 197 | +``` |
| 198 | + |
| 199 | +TODO |
| 200 | + |
| 201 | +```c |
| 202 | +TODO |
| 203 | +``` |
| 204 | + |
| 205 | +</section> |
| 206 | + |
| 207 | +<!-- /.usage --> |
| 208 | + |
| 209 | +<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 210 | + |
| 211 | +<section class="notes"> |
| 212 | + |
| 213 | +</section> |
| 214 | + |
| 215 | +<!-- /.notes --> |
| 216 | + |
| 217 | +<!-- C API usage examples. --> |
| 218 | + |
| 219 | +<section class="examples"> |
| 220 | + |
| 221 | +### Examples |
| 222 | + |
| 223 | +```c |
| 224 | +TODO |
| 225 | +``` |
| 226 | + |
| 227 | +</section> |
| 228 | + |
| 229 | +<!-- /.examples --> |
| 230 | + |
| 231 | +</section> |
| 232 | + |
| 233 | +<!-- /.c --> |
| 234 | + |
| 235 | +<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. --> |
| 236 | + |
| 237 | +<section class="related"> |
| 238 | + |
| 239 | +</section> |
| 240 | + |
| 241 | +<!-- /.related --> |
| 242 | + |
| 243 | +<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 244 | + |
| 245 | +<section class="links"> |
| 246 | + |
| 247 | +[lapack]: https://www.netlib.org/lapack/explore-html/ |
| 248 | + |
| 249 | +[lapack-dlassq]: https://www.netlib.org/lapack/explore-html/d8/d76/group__lassq_gae8f40b0a34771b4f2d9c863de3af7be5.html#gae8f40b0a34771b4f2d9c863de3af7be5 |
| 250 | + |
| 251 | +[mdn-float64array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array |
| 252 | + |
| 253 | +[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray |
| 254 | + |
| 255 | +</section> |
| 256 | + |
| 257 | +<!-- /.links --> |
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