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ddot

Calculate the dot product of two double-precision floating-point vectors.

The dot product (or scalar product) is defined as

$$\mathbf{x}\cdot\mathbf{y} = \sum_{i=0}^{N-1} x_i y_i = x_0 y_0 + x_1 y_1 + \ldots + x_{N-1} y_{N-1}$$

Installation

npm install @stdlib/blas-ddot

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var ddot = require( '@stdlib/blas-ddot' );

ddot( x, y )

Calculates the dot product of two double-precision floating-point vectors x and y.

var Float64Array = require( '@stdlib/array-float64' );
var array = require( '@stdlib/ndarray-array' );

var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] ) );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] ) );

var z = ddot( x, y );
// returns -5.0

The function has the following parameters:

• x: a 1-dimensional ndarray whose underlying data type is float64.
• y: a 1-dimensional ndarray whose underlying data type is float64.

If provided empty vectors, the function returns 0.0.

var Float64Array = require( '@stdlib/array-float64' );
var array = require( '@stdlib/ndarray-array' );

var x = array( new Float64Array() );
var y = array( new Float64Array() );

var z = ddot( x, y );
// returns 0.0

Notes

• ddot() provides a higher-level interface to the BLAS level 1 function ddot.

Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var Float64Array = require( '@stdlib/array-float64' );
var array = require( '@stdlib/ndarray-array' );
var ddot = require( '@stdlib/blas-ddot' );

var x = array( new Float64Array( 10 ) );
var y = array( new Float64Array( 10 ) );

var rand1 = discreteUniform.factory( 0, 100 );
var rand2 = discreteUniform.factory( 0, 10 );

var i;
for ( i = 0; i < x.length; i++ ) {
    x.set( i, rand1() );
    y.set( i, rand2() );
}
console.log( x.toString() );
console.log( y.toString() );

var z = ddot( x, y );
console.log( z );

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See Also

• @stdlib/blas-base/ddot: calculate the dot product of two double-precision floating-point vectors.
• @stdlib/blas-gdot: calculate the dot product of two vectors.
• @stdlib/blas-sdot: calculate the dot product of two single-precision floating-point vectors.

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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

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.