drotm

Apply a modified Givens plane rotation.

Usage

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

drotm.main( N, x, strideX, y, strideY, param )

Applies a modified Givens plane rotation.

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

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

drotm.main( 2, x, 2, y, 1, param );
// x => <Float64Array>[ ~-17.0, 2.0, ~-18.0, 4.0, 5.0 ]
// y => <Float64Array>[ ~8.0, ~13.0, 8.0, 9.0, 10.0 ]

The function has the following parameters:

  • N: number of indexed elements.
  • x: input Float64Array.
  • strideX: index increment for x.
  • y: input Float64Array.
  • strideY: index increment for y.
  • param: parameters for the modified Givens transformation

The N and stride parameters determine how values in the strided arrays are accessed at runtime. For example, to apply a modified Givens plane rotation to every other element,

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

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

drotm.main( 3, x, 2, y, 2, param );
// x => <Float64Array>[ ~-20.0, 2.0, ~-24.0, 4.0, ~-28.0, 6.0 ]
// y => <Float64Array>[ ~9.0, 8.0, ~15.0, 10.0, ~21.0, 12.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

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

// Initial arrays...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y0 = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float64Array( [ 1.0, 0.0, 2.0, 3.0, 0.0 ] );

// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element

drotm.main( 2, x1, 1, y1, 1, param );
// x0 => <Float64Array>[ 1.0, ~9.0, ~10.0, 4.0, 5.0 ]
// y0 => <Float64Array>[ 6.0, 7.0, 8.0, ~-2.0, ~-3.0 ]

drotm.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, param )

Applies a modified Givens plane rotation using alternative indexing semantics.

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

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

drotm.ndarray( 2, x, 1, 0, y, 2, 1, param );
// x => <Float64Array>[ ~-20.0, ~-25.0, 3.0, 4.0, 5.0 ]
// y => <Float64Array>[ 6.0, ~9.0, 8.0, ~13.0, 10.0 ]

The function has the following additional parameters:

  • offsetX: starting index for x.
  • offsetY: starting index for y.

While 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 apply a modified Givens plane rotation to every other element starting from the second element,

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

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

drotm.ndarray( 3, x, 2, 1, y, 2, 1, param );
// x => <Float64Array>[ 1.0, ~-22.0, 3.0, ~-26.0, 5.0, ~-30.0 ]
// y => <Float64Array>[ 7.0, ~12.0, 9.0, ~18.0, 11.0, ~24.0 ]

Module

drotm.Module( memory )

Returns a new WebAssembly module wrapper instance which uses the provided WebAssembly memory instance as its underlying memory.

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 drotm.Module( mem );
// returns <Module>

// Initialize the routine:
mod.initializeSync();

drotm.Module.prototype.main( N, xp, sx, yp, sy, pp )

Applies a modified Givens plane rotation.

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 drotm.Module( mem );
// returns <Module>

// Initialize the routine:
mod.initializeSync();

// Define a vector data type:
var dtype = 'float64';

// Specify a vector length:
var N = 5;

// Define pointers (i.e., byte offsets) for storing three vectors:
var xptr = 0;
var yptr = N * bytesPerElement( dtype );
var pptr = 2 * N * bytesPerElement( dtype );

// Write vector values to module memory:
mod.write( xptr, oneTo( N, dtype ) );
mod.write( yptr, ones( N, dtype ) );
mod.write( pptr, ones( 5, dtype ) );

// Perform computation:
mod.main( N, xptr, 1, yptr, 1, pptr );

// Read out the results:
var viewX = zeros( N, dtype );
var viewY = zeros( N, dtype );
mod.read( xptr, viewX );
mod.read( yptr, viewY );

console.log( viewX );
// => <Float64Array>[ 2.0, 3.0, 4.0, 5.0, 6.0 ]

console.log( viewY );
// => <Float64Array>[ 0.0, -1.0, -2.0, -3.0, -4.0 ]

The function has the following parameters:

  • N: number of indexed elements.
  • xp: input Float64Array pointer (i.e., byte offset).
  • sx: index increment for x.
  • yp: input Float64Array pointer (i.e., byte offset).
  • sy: index increment for y.
  • pp: parameter Float64Array pointer (i.e., byte offset).

drotm.Module.prototype.ndarray( N, xp, sx, ox, yp, sy, oy, pp )

Applies a modified Givens plane rotation using alternative indexing semantics.

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 drotm.Module( mem );
// returns <Module>

// Initialize the routine:
mod.initializeSync();

// Define a vector data type:
var dtype = 'float64';

// Specify a vector length:
var N = 5;

// Define pointers (i.e., byte offsets) for storing three vectors:
var xptr = 0;
var yptr = N * bytesPerElement( dtype );
var pptr = 2 * N * bytesPerElement( dtype );

// Write vector values to module memory:
mod.write( xptr, oneTo( N, dtype ) );
mod.write( yptr, ones( N, dtype ) );
mod.write( pptr, ones( 5, dtype ) );

// Perform computation:
mod.ndarray( N, xptr, 1, 0, yptr, 1, 0, pptr );

// Read out the results:
var viewX = zeros( N, dtype );
var viewY = zeros( N, dtype );
mod.read( xptr, viewX );
mod.read( yptr, viewY );

console.log( viewX );
// => <Float64Array>[ 2.0, 3.0, 4.0, 5.0, 6.0 ]

console.log( viewY );
// => <Float64Array>[ 0.0, -1.0, -2.0, -3.0, -4.0 ]

The function has the following additional parameters:

  • ox: starting index for x.
  • oy: starting index for y.

Notes

  • If N <= 0, x and y are left unchanged.
  • This package implements routines using WebAssembly. When provided arrays which are not allocated on a drotm 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/drotm. 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/drotm. 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.
  • drotm() corresponds to the BLAS level 1 function drotm.

Examples

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

var opts = {
    'dtype': 'float64'
};
var x = discreteUniform( 10, 0, 100, opts );
console.log( x );

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

var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

drotm.ndarray( x.length, x, 1, 0, y, -1, y.length-1, param );
console.log( y );
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