stride2offset

Determine the index offset which specifies the location of the first indexed value in a strided array.

Installation

npm install @stdlib/strided-base-stride2offset

Usage

var stride2offset = require( '@stdlib/strided-base-stride2offset' );

stride2offset( N, stride )

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

var offset = stride2offset( 10, 10 );
// returns 0

offset = stride2offset( 10, -10 );
// returns 90

Examples

var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var stride2offset = require( '@stdlib/strided-base-stride2offset' );

var opts = {
    'dtype': 'generic'
};

// Define the number of indexed elements:
var N = 100;

// Define a maximum stride length:
var maxStride = 10;

// Create an array of random integers which can accommodate the maximum stride length:
var arr = discreteUniform( N*maxStride, 0, 255, opts );

// Generate random stride lengths:
var strides = discreteUniform( 10, -maxStride, maxStride, opts );

// Resolve values in the data array for the first indexed element based on various stride lengths...
var offset;
var i;
for ( i = 0; i < strides.length; i++ ) {
    offset = stride2offset( N, strides[ i ] );
    console.log( 'stride = %d. arr[%d] = %d.', strides[ i ], offset, arr[ offset ] );
}

C APIs

Usage

#include "stdlib/strided/base/stride2offset.h"

stdlib_strided_stride2offset( N, stride )

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

#include "stdlib/strided/base/stride2offset.h"
#include <stdint.h>

int64_t offset = stdlib_strided_stride2offset( 10, -10 );
// returns 90

The function accepts the following arguments:

• N: [in] int64_t number of indexed elements.
• stride [in] int64_t index increment.

int64_t stdlib_strided_stride2offset( int64_t N, int64_t stride );

Examples

#include "stdlib/strided/base/stride2offset.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>

int main( void ) {
    // Specify the number of indexed elements:
    int64_t N = 6;

    // Define a stride:
    int64_t stride = -2;

    // Compute the offset:
    int64_t offset = stdlib_strided_stride2offset( N, stride )

    // Print the results:
    printf( "stride: %"PRId64" => offset: %"PRId64"\n", stride, 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.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.