130 lines
3.0 KiB
Markdown
130 lines
3.0 KiB
Markdown
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<!--
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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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# Iteration Order
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> Given a stride array, determine array iteration order.
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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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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var iterationOrder = require( '@stdlib/ndarray/base/iteration-order' );
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```
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#### iterationOrder( strides )
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Returns the array iteration order.
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```javascript
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var o = iterationOrder( [ 2, 1 ] );
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// returns 1
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o = iterationOrder( [ -2, 1 ] );
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// returns 0
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o = iterationOrder( [ -2, -1 ] );
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// returns -1
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```
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The function returns one of the following values:
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- `0`: unordered (strides are of mixed sign).
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- `1`: left-to-right iteration order (strides are all nonnegative).
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- `-1`: right-to-left iteration order (strides are all negative).
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</section>
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<!-- /.usage -->
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<!-- Package 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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<!-- Package usage examples. -->
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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 shape2strides = require( '@stdlib/ndarray/base/shape2strides' );
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var randu = require( '@stdlib/random/base/randu' );
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var iterationOrder = require( '@stdlib/ndarray/base/iteration-order' );
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var strides;
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var shape;
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var out;
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var i;
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var j;
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shape = [ 0, 0, 0 ];
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shape[ 0 ] = discreteUniform( 1, 10 );
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shape[ 1 ] = discreteUniform( 1, 10 );
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shape[ 2 ] = discreteUniform( 1, 10 );
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strides = shape2strides( shape, 'row-major' );
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for ( i = 0; i < 100; i++ ) {
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j = discreteUniform( 0, shape.length-1 );
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strides[ j ] *= ( randu() < 0.5 ) ? -1 : 1;
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out = iterationOrder( strides );
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console.log( 'strides: %s => %d', strides.join( ',' ), out );
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}
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```
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</section>
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<!-- /.examples -->
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<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="references">
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</section>
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<!-- /.references -->
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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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</section>
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<!-- /.links -->
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