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# gdot

> Calculate the dot product of two vectors.

<section class="intro">

The [dot product][dot-product] (or scalar product) is defined as

<!-- <equation class="equation" label="eq:dot_product" align="center" raw="\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}" alt="Dot product definition."> -->

<div class="equation" align="center" data-raw-text="\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}" data-equation="eq:dot_product">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@b7a453f335bade718a3f48a61658d1564dc3f786/lib/node_modules/@stdlib/blas/gdot/docs/img/equation_dot_product.svg" alt="Dot product definition.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var gdot = require( '@stdlib/blas/gdot' );
```

#### gdot( x, y )

Calculates the dot product of vectors `x` and `y`.

```javascript
var Int32Array = require( '@stdlib/array/int32' );
var array = require( '@stdlib/ndarray/array' );

var x = array( new Int32Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] ) );
var y = array( new Int32Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] ) );

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

The function has the following parameters:

-   **x**: a 1-dimensional [`ndarray`][@stdlib/ndarray/array] or an array-like object.
-   **y**: a 1-dimensional [`ndarray`][@stdlib/ndarray/array] or an array-like object.

If provided empty vectors, the function returns `0.0`.

```javascript
var z = gdot( [], [] );
// returns 0.0
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   `gdot()` corresponds to the [BLAS][blas] level 1 function [`ddot`][ddot] with the exception that this implementation works with any array type, not just Float64Arrays.
-   In general, for best performance, especially for large vectors, provide 1-dimensional [`ndarrays`][@stdlib/ndarray/array] whose underlying data type is either `float64` or `float32`.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var gdot = require( '@stdlib/blas/gdot' );

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

var x = [];
var y = [];
var i;
for ( i = 0; i < 10; i++ ) {
    x.push( rand1() );
    y.push( rand2() );
}
console.log( x );
console.log( y );

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

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/blas/base/gdot`][@stdlib/blas/base/gdot]</span><span class="delimiter">: </span><span class="description">calculate the dot product of two vectors.</span>
-   <span class="package-name">[`@stdlib/blas/ddot`][@stdlib/blas/ddot]</span><span class="delimiter">: </span><span class="description">calculate the dot product of two double-precision floating-point vectors.</span>
-   <span class="package-name">[`@stdlib/blas/sdot`][@stdlib/blas/sdot]</span><span class="delimiter">: </span><span class="description">calculate the dot product of two single-precision floating-point vectors.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[dot-product]: https://en.wikipedia.org/wiki/Dot_product

[blas]: http://www.netlib.org/blas

[ddot]: http://www.netlib.org/lapack/explore-html/df/d28/group__single__blas__level1.html

[@stdlib/ndarray/array]: https://www.npmjs.com/package/@stdlib/ndarray-array

<!-- <related-links> -->

[@stdlib/blas/base/gdot]: https://github.com/stdlib-js/blas/tree/main/base/gdot

[@stdlib/blas/ddot]: https://github.com/stdlib-js/blas/tree/main/ddot

[@stdlib/blas/sdot]: https://github.com/stdlib-js/blas/tree/main/sdot

<!-- </related-links> -->

</section>

<!-- /.links -->
