98 lines
2.3 KiB
Markdown
98 lines
2.3 KiB
Markdown
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@license Apache-2.0
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Copyright (c) 2018 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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# uimuldw
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> Compute the double word product of two unsigned 32-bit integers.
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<section class="intro">
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</section>
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<!-- /.intro -->
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<section class="usage">
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## Usage
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```javascript
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var uimuldw = require( '@stdlib/math/base/special/uimuldw' );
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```
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#### uimuldw( \[out,] a, b )
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Multiplies two unsigned 32-bit integers and returns an `array` of two unsigned 32-bit integers (in big endian order) which represents the unsigned 64-bit integer product.
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```javascript
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var v = uimuldw( 1, 10 );
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// returns [ 0, 10 ]
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v = uimuldw( 0x80000000, 0x80000000 ); // 2^31 * 2^31 = 4611686018427388000 => 32-bit integer overflow
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// returns [ 1073741824, 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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- When computing the product of 32-bit integer values in double-precision floating-point format (the default JavaScript numeric data type), computing the double word product is necessary in order to **avoid** exceeding the [maximum safe double-precision floating-point integer value][@stdlib/constants/float64/max-safe-integer].
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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 lpad = require( '@stdlib/string/left-pad' );
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var uimuldw = require( '@stdlib/math/base/special/uimuldw' );
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var i;
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var j;
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var y;
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for ( i = 0xFFFFFFF0; i < 0xFFFFFFFF; i++ ) {
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for ( j = i; j < 0xFFFFFFFF; j++) {
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y = uimuldw( i, j );
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console.log( '%d x %d = 0x%s%s', i, j, lpad( y[0].toString( 16 ), 8, '0' ), lpad( y[1].toString( 16 ), 8, '0' ) );
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}
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}
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[@stdlib/constants/float64/max-safe-integer]: https://www.npmjs.com/package/@stdlib/constants-float64-max-safe-integer
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</section>
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<!-- /.links -->
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