ddot

Computes the dot product of x and y.

The algebraic definition of the dot product between two vectors x and y is

Installation

$ npm install blas-ddot

Usage

var ddot = require( 'blas-ddot' );

ddot( N, x, strideX, offsetX, y, strideY, offsetY )

Computes the dot product of x and y.

var x = [ 1, 2, 3, 4, 5 ];
var y = [ 6, 7, 8, 9, 10 ];

var val = ddot( x.length, x, 1, 0, y, 1, 0 );
// returns 6+14+24+36+50 = 130

The function accepts the following parameters:

• N: number of accessed elements.
• x: input array or typed array.
• strideX: index increment for x.
• offsetX: starting index for x.
• y: input array or typed array.
• strideY: index increment for y.
• offsetY: starting index for y.

The N, stride, and offset parameters determine how elements are accessed during runtime. For example, to compute the dot product between every other element in x starting from its second element and the last N elements in y starting from its last element,

var x = [ 1, 2, 3, 4, 5, 6 ];
var y = [ 7, 8, 9, 10, 11, 12 ];

var N = Math.floor( x.length / 2 );

var val = ddot( N, x, 2, 1, y, -1, y.length-1 );
// returns 24+44+60 = 128

If N <= 0, the function returns undefined.

Notes

• This module corresponds to the BLAS level 1 function ddot.

Examples

var ddot = require( 'blas-ddot' );

var x;
var y;
var i;

x = new Float64Array( 10 );
y = new Float64Array( 10 );
for ( i = 0; i < x.length; i++ ) {
	x[ i ] = Math.round( Math.random()*500 );
	y[ i ] = Math.round( Math.random()*10 );
}
// Compute the dot product between `x` and the reverse of `y`:
console.log( ddot( x.length, x, 1, 0, y, -1, y.length-1 ) );

To run the example code from the top-level application directory,

$ node ./examples/index.js

Tests

Unit

This repository uses tape for unit tests. To run the tests, execute the following command in the top-level application directory:

$ make test

All new feature development should have corresponding unit tests to validate correct functionality.

Test Coverage

This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:

$ make test-cov

Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,

$ make view-cov

Browser Support

This repository uses Testling for browser testing. To run the tests in a (headless) local web browser, execute the following command in the top-level application directory:

$ make test-browsers

To view the tests in a local web browser,

$ make view-browser-tests

License

MIT license.

Copyright

Copyright © 2016. The Compute.io Authors.