@stdlib/ndarray-base-strides2offset NPM

strides2offset

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

Installation

npm install @stdlib/ndarray-base-strides2offset

Usage

var strides2offset = require( '@stdlib/ndarray-base-strides2offset' );

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

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var shape2strides = require( '@stdlib/ndarray-base-shape2strides' );
var numel = require( '@stdlib/ndarray-base-numel' );
var randu = require( '@stdlib/random-base-randu' );
var strides2offset = require( '@stdlib/ndarray-base-strides2offset' );

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 for JavaScript and Node.js, 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.