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strides2offset

Determine the index offset which specifies the location of the first indexed value in a multidimensional array based on a stride array.

Usage

import strides2offset from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-base-strides2offset@deno/mod.js';

strides2offset( shape, strides )

Returns the index offset which specifies the location of the first indexed value in a multidimensional array.

var offset = strides2offset( [ 3, 2 ], [ 2, 1 ] );
// returns 0

offset = strides2offset( [ 3, 2 ], [ -2, 1 ] );
// returns 4

Examples

import discreteUniform from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-base-discrete-uniform@deno/mod.js';
import shape2strides from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-base-shape2strides@deno/mod.js';
import numel from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-base-numel@deno/mod.js';
import randu from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-base-randu@deno/mod.js';
import strides2offset from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-base-strides2offset@deno/mod.js';

var strides;
var offset;
var shape;
var len;
var arr;
var i;
var j;

shape = [ 0, 0, 0 ];
shape[ 0 ] = discreteUniform( 1, 10 );
shape[ 1 ] = discreteUniform( 1, 10 );
shape[ 2 ] = discreteUniform( 1, 10 );

strides = shape2strides( shape, 'row-major' );
len = numel( shape );

arr = [];
for ( i = 0; i < len; i++ ) {
    arr.push( i );
}
for ( i = 0; i < 100; i++ ) {
    j = discreteUniform( 0, shape.length-1 );
    strides[ j ] *= ( randu() < 0.5 ) ? -1 : 1;
    offset = strides2offset( shape, strides );
    console.log( 'arr[0][0][0] = %d', arr[ offset ] );
}

Notice

This package is part of stdlib, a standard library with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2025. The Stdlib Authors.

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