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https://github.com/stdlib-js/blas-base-sdot-wasm

Compute the dot product of `x` and `y`.
https://github.com/stdlib-js/blas-base-sdot-wasm

algebra array blas dot float float32 float32array javascript level-1 linear math mathematics ndarray node node-js nodejs sdot stdlib subroutines vector

Last synced: 8 days ago
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Compute the dot product of `x` and `y`.

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README 

        



  

    About stdlib...

  

  
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# sdot



[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] 



> Compute the dot product of `x` and `y`.



## Installation



```bash

npm install @stdlib/blas-base-sdot-wasm

```



Alternatively,



-   To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).



The [branches.md][branches-url] 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



```javascript

var sdot = require( '@stdlib/blas-base-sdot-wasm' );

```



#### sdot.main( N, x, strideX, y, strideY )



Computes the dot product of `x` and `y`.



```javascript

var Float32Array = require( '@stdlib/array-float32' );



var x = new Float32Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] );

var y = new Float32Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] );



var z = sdot.main( x.length, x, 1, y, 1 );

// returns -5.0

```



The function has the following parameters:



-   **N**: number of indexed elements.

-   **x**: first input [`Float32Array`][@stdlib/array/float32].

-   **strideX**: index increment for `x`.

-   **y**: second input [`Float32Array`][@stdlib/array/float32].

-   **strideY**: index increment for `y`.



The `N` and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to calculate the dot product of every other value in `x` and the first `N` elements of `y` in reverse order,



```javascript

var Float32Array = require( '@stdlib/array-float32' );



var x = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var y = new Float32Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );



var z = sdot.main( 3, x, 2, y, -1 );

// returns 9.0

```



Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.



```javascript

var Float32Array = require( '@stdlib/array-float32' );



// Initial arrays...

var x0 = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var y0 = new Float32Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );



// Create offset views...

var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var y1 = new Float32Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element



var z = sdot.main( 3, x1, -2, y1, 1 );

// returns 128.0

```



#### sdot.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )



Computes the dot product of `x` and `y` using alternative indexing semantics.



```javascript

var Float32Array = require( '@stdlib/array-float32' );



var x = new Float32Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] );

var y = new Float32Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] );



var z = sdot.ndarray( x.length, x, 1, 0, y, 1, 0 );

// returns -5.0

```



The function has the following additional parameters:



-   **offsetX**: starting index for `x`.

-   **offsetY**: starting index for `y`.



While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to calculate the dot product of every other value in `x` starting from the second value with the last 3 elements in `y` in reverse order



```javascript

var Float32Array = require( '@stdlib/array-float32' );



var x = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var y = new Float32Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );



var z = sdot.ndarray( 3, x, 2, 1, y, -1, y.length-1 );

// returns 128.0

```



* * *



### Module



#### sdot.Module( memory )



Returns a new WebAssembly [module wrapper][@stdlib/wasm/module-wrapper] instance which uses the provided WebAssembly [memory][@stdlib/wasm/memory] instance as its underlying memory.



```javascript

var Memory = require( '@stdlib/wasm-memory' );



// Create a new memory instance with an initial size of 10 pages (640KiB) and a maximum size of 100 pages (6.4MiB):

var mem = new Memory({

    'initial': 10,

    'maximum': 100

});



// Create a BLAS routine:

var mod = new sdot.Module( mem );

// returns 



// Initialize the routine:

mod.initializeSync();

```



#### sdot.Module.prototype.main( N, xp, sx, yp, sy )



Computes the dot product of `x` and `y`.



```javascript

var Memory = require( '@stdlib/wasm-memory' );

var oneTo = require( '@stdlib/array-one-to' );

var ones = require( '@stdlib/array-ones' );

var zeros = require( '@stdlib/array-zeros' );

var bytesPerElement = require( '@stdlib/ndarray-base-bytes-per-element' );



// Create a new memory instance with an initial size of 10 pages (640KiB) and a maximum size of 100 pages (6.4MiB):

var mem = new Memory({

    'initial': 10,

    'maximum': 100

});



// Create a BLAS routine:

var mod = new sdot.Module( mem );

// returns 



// Initialize the routine:

mod.initializeSync();



// Define a vector data type:

var dtype = 'float32';



// Specify a vector length:

var N = 5;



// Define pointers (i.e., byte offsets) for storing two vectors:

var xptr = 0;

var yptr = N * bytesPerElement( dtype );



// Write vector values to module memory:

mod.write( xptr, oneTo( N, dtype ) );

mod.write( yptr, ones( N, dtype ) );



// Perform computation:

var z = mod.main( N, xptr, 1, yptr, 1 );



console.log( z );

```



The function has the following parameters:



-   **N**: number of indexed elements.

-   **xp**: first input [`Float32Array`][@stdlib/array/float32] pointer (i.e., byte offset).

-   **sx**: index increment for `x`.

-   **yp**: second input [`Float32Array`][@stdlib/array/float32] pointer (i.e., byte offset).

-   **sy**: index increment for `y`.



#### sdot.Module.prototype.ndarray( N, xp, sx, ox, yp, sy, oy )



Computes the dot product of `x` and `y` using alternative indexing semantics.



```javascript

var Memory = require( '@stdlib/wasm-memory' );

var oneTo = require( '@stdlib/array-one-to' );

var ones = require( '@stdlib/array-ones' );

var zeros = require( '@stdlib/array-zeros' );

var bytesPerElement = require( '@stdlib/ndarray-base-bytes-per-element' );



// Create a new memory instance with an initial size of 10 pages (640KiB) and a maximum size of 100 pages (6.4MiB):

var mem = new Memory({

    'initial': 10,

    'maximum': 100

});



// Create a BLAS routine:

var mod = new sdot.Module( mem );

// returns 



// Initialize the routine:

mod.initializeSync();



// Define a vector data type:

var dtype = 'float32';



// Specify a vector length:

var N = 5;



// Define pointers (i.e., byte offsets) for storing two vectors:

var xptr = 0;

var yptr = N * bytesPerElement( dtype );



// Write vector values to module memory:

mod.write( xptr, oneTo( N, dtype ) );

mod.write( yptr, ones( N, dtype ) );



// Perform computation:

var z = mod.ndarray( N, xptr, 1, 0, yptr, 1, 0 );



console.log( z );

```



The function has the following additional parameters:



-   **ox**: starting index for `x`.

-   **oy**: starting index for `y`.



* * *



## Notes



-   If `N <= 0`, both `main` and `ndarray` methods return `0.0`.

-   This package implements routines using WebAssembly. When provided arrays which are not allocated on a `sdot` module memory instance, data must be explicitly copied to module memory prior to computation. Data movement may entail a performance cost, and, thus, if you are using arrays external to module memory, you should prefer using [`@stdlib/blas-base/sdot`][@stdlib/blas/base/sdot]. However, if working with arrays which are allocated and explicitly managed on module memory, you can achieve better performance when compared to the pure JavaScript implementations found in [`@stdlib/blas/base/sdot`][@stdlib/blas/base/sdot]. Beware that such performance gains may come at the cost of additional complexity when having to perform manual memory management. Choosing between implementations depends heavily on the particular needs and constraints of your application, with no one choice universally better than the other.

-   `sdot()` corresponds to the [BLAS][blas] level 1 function [`sdot`][sdot].



* * *



## Examples



```javascript

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

var sdot = require( '@stdlib/blas-base-sdot-wasm' );



var opts = {

    'dtype': 'float32'

};

var x = discreteUniform( 10, 0, 100, opts );

console.log( x );



var y = discreteUniform( x.length, 0, 10, opts );

console.log( y );



var z = sdot.ndarray( x.length, x, 1, 0, y, -1, y.length-1 );

console.log( z );

```



* * *



## Notice



This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].



#### Community



[![Chat][chat-image]][chat-url]



---



## License



See [LICENSE][stdlib-license].



## Copyright



Copyright © 2016-2024. The Stdlib [Authors][stdlib-authors].



[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-base-sdot-wasm.svg

[npm-url]: https://npmjs.org/package/@stdlib/blas-base-sdot-wasm



[test-image]: https://github.com/stdlib-js/blas-base-sdot-wasm/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/blas-base-sdot-wasm/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-base-sdot-wasm/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/blas-base-sdot-wasm?branch=main



[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im



[stdlib]: https://github.com/stdlib-js/stdlib



[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors



[umd]: https://github.com/umdjs/umd

[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules



[deno-url]: https://github.com/stdlib-js/blas-base-sdot-wasm/tree/deno

[deno-readme]: https://github.com/stdlib-js/blas-base-sdot-wasm/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/blas-base-sdot-wasm/tree/umd

[umd-readme]: https://github.com/stdlib-js/blas-base-sdot-wasm/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/blas-base-sdot-wasm/tree/esm

[esm-readme]: https://github.com/stdlib-js/blas-base-sdot-wasm/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/blas-base-sdot-wasm/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-base-sdot-wasm/main/LICENSE



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



[sdot]: https://www.netlib.org/lapack/explore-html/d1/dcc/group__dot_gaa145c21fd5f5b672ac0b4560154682dd.html#gaa145c21fd5f5b672ac0b4560154682dd



[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray



[@stdlib/array/float32]: https://github.com/stdlib-js/array-float32



[@stdlib/wasm/memory]: https://github.com/stdlib-js/wasm-memory



[@stdlib/wasm/module-wrapper]: https://github.com/stdlib-js/wasm-module-wrapper



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