blas-daxpy

daxpy

Multiplies x and a constant alpha and adds the result to y.

Installation

$ npm install blas-daxpy

Usage

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

daxpy( N, alpha, x, strideX, offsetY, y, strideY, offsetY )

Multiplies x and a constant alpha and adds the result to y.

var x = [ 1, 2, 3, 4, 5 ];
var y = [ 1, 1, 1, 1, 1 ];

daxpy( x.length, 5, x, 1, 0, y, 1, 0 );
// y => [ 6, 11, 16, 21, 26 ]

The function accepts the following parameters:

• N: number of indexed elements.
• alpha: numeric constant.
• 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 which elements in x and y are accessed at runtime. For example, to multiply every other element of x starting from its second element by alpha and add the result to y starting from its last element,

var x = [ 1, 2, 3, 4, 5, 6 ];
var y = [ 1, 1, 1, 1, 1, 1 ];

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

daxpy( N, 5, x, 2, 1, y, -1, y.length-1 );
// y => [ 1, 1, 1, 31, 21, 11 ]

If N <= 0, the function returns undefined.

Notes

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

Examples

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

var x;
var y;
var i;

x = new Float64Array( 10 );
y = new Float32Array( 10 );
for ( i = 0; i < x.length; i++ ) {
	x[ i ] = Math.round( Math.random() * 100 );
	y[ i ] = Math.round( Math.random() * 10 );
}
console.log( x );
console.log( y );

daxpy( x.length, 5, x, 1, 0, y, -1, y.length-1 );
console.log( y );

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

$ node ./examples/index.js

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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

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License

MIT license.

Copyright

Copyright © 2016. The Compute.io Authors.