Iteration Order

Given a stride array, determine array iteration order.

Usage

var iterationOrder = require( '@stdlib/ndarray/base/iteration-order' );

iterationOrder( strides )

Returns the array iteration order.

var o = iterationOrder( [ 2, 1 ] );
// returns 1

o = iterationOrder( [ -2, 1 ] );
// returns 0

o = iterationOrder( [ -2, -1 ] );
// returns -1

The function returns one of the following values:

  • 0: unordered (strides are of mixed sign).
  • 1: left-to-right iteration order (strides are all nonnegative).
  • -1: right-to-left iteration order (strides are all negative).

Examples

var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var shape2strides = require( '@stdlib/ndarray/base/shape2strides' );
var randu = require( '@stdlib/random/base/randu' );
var iterationOrder = require( '@stdlib/ndarray/base/iteration-order' );

var strides;
var shape;
var out;
var i;
var j;

shape = new Array( 3 );
shape[ 0 ] = discreteUniform( 1, 10 );
shape[ 1 ] = discreteUniform( 1, 10 );
shape[ 2 ] = discreteUniform( 1, 10 );

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

for ( i = 0; i < 100; i++ ) {
    j = discreteUniform( 0, shape.length-1 );
    strides[ j ] *= ( randu() < 0.5 ) ? -1 : 1;
    out = iterationOrder( strides );
    console.log( 'strides: %s => %d', strides.join( ',' ), out );
}