cscal

Scale a single-precision complex floating-point vector by a single-precision complex floating-point constant.

Usage

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

cscal.main( N, ca, cx, strideX )

Scales values from cx by ca.

var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );
var realf = require( '@stdlib/complex/float32/real' );
var imagf = require( '@stdlib/complex/float32/imag' );

// Define a strided array:
var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

// Define a scalar constant:
var ca = new Complex64( 2.0, 2.0 );

// Perform operation:
cscal.main( cx.length, ca, cx, 1 );

var v = cx.get( 0 );
// returns <Complex64>

var re = realf( v );
// returns -2.0

var im = imagf( v );
// returns 6.0

The function has the following parameters:

  • N: number of indexed elements.
  • ca: scalar Complex64 constant.
  • cx: input Complex64Array.
  • strideX: index increment for cx.

The N and stride parameters determine which elements in the input strided array are accessed at runtime. For example, to scale every other value in cx by ca,

var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );
var realf = require( '@stdlib/complex/float32/real' );
var imagf = require( '@stdlib/complex/float32/imag' );

// Define a strided array:
var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

// Define a scalar constant:
var ca = new Complex64( 2.0, 0.0 );

// Perform operation:
cscal.main( 2, ca, cx, 2 );

var v = cx.get( 2 );
// returns <Complex64>

var re = realf( v );
// returns 10.0

var im = imagf( v );
// returns 12.0

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

var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );
var realf = require( '@stdlib/complex/float32/real' );
var imagf = require( '@stdlib/complex/float32/imag' );

// Initial array:
var cx0 = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

// Define a scalar constant:
var ca = new Complex64( 2.0, 2.0 );

// Create an offset view:
var cx1 = new Complex64Array( cx0.buffer, cx0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Scales every other value from `cx1` by `ca`...
cscal.main( 3, ca, cx1, 1 );

var z = cx0.get( 1 );
// returns <Complex64>

var re = realf( z );
// returns -2.0

var im = imagf( z );
// returns 14.0

dscal.ndarray( N, ca, cx, strideX, offsetX )

Scales values from cx by ca using alternative indexing semantics.

var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );
var realf = require( '@stdlib/complex/float32/real' );
var imagf = require( '@stdlib/complex/float32/imag' );

// Define a strided array:
var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

// Define a scalar constant:
var ca = new Complex64( 2.0, 2.0 );

// Perform operation:
cscal.main( cx.length, ca, cx, 1 );

var v = cx.get( 0 );
// returns <Complex64>

var re = realf( v );
// returns -2.0

var im = imagf( v );
// returns 6.0

The function has the following additional parameters:

  • offsetX: starting index for cx.

While typed array views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to scale every other value in the input strided array starting from the second element,

var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );
var realf = require( '@stdlib/complex/float32/real' );
var imagf = require( '@stdlib/complex/float32/imag' );

var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var ca = new Complex64( 2.0, 2.0 );

cscal.ndarray( 2, ca, cx, 2, 1 );

var z = cx.get( 3 );
// returns <Complex64>

var re = realf( z );
// returns -2.0

var im = imagf( z );
// returns 30.0

Module

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

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

cscal.Module.prototype.main( N, cap, cxp, sx )

Scales values from cx by ca .

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' );
var Float32Array = require( '@stdlib/array/float32' );
var Complex64Array = require( '@stdlib/array/complex64' );
var reinterpretComplex64 = require( '@stdlib/strided/base/reinterpret-complex64' );
var cscal = require( '@stdlib/blas/base/cscal-wasm' );

// Create a new memory instance with an initial size of 10 pages (320KiB) and a maximum size of 100 pages (6.4MiB):
var mem = new Memory({
    'initial': 10,
    'maximum': 100
});

// Create a BLAS routine:
var mod = new cscal.Module( mem );
// returns <Module>

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

// Define a vector data type:
var dtype = 'complex64';

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

// Define a pointer (i.e., byte offset) for storing the input vector:
var xptr = 0;

// Define a pointer for storing a complex number:
var zptr = N * bytesPerElement( dtype );

// Write vector values to module memory:
var xbuf = oneTo( N*2, 'float32' );
var x = new Complex64Array( xbuf.buffer );
mod.write( xptr, x );

// Write a complex number to module memory:
mod.write( zptr, new Float32Array( [ 2.0, 2.0 ] ) );

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

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

console.log( reinterpretComplex64( view, 0 ) );
// => <Float32Array>[ -2.0, 6.0, -2.0, 14.0, -2.0, 22.0, -2.0, 30.0, -2.0, 38.0 ]

The function has the following parameters:

  • N: number of indexed elements.
  • cap: pointer (i.e., byte offset) to a scalar Complex64 constant.
  • cxp: input Complex64Array pointer (i.e., byte offset).
  • sx: index increment for cx.

cscal.Module.prototype.ndarray( N, cap, cxp, sx, ox )

Scales values from cx by ca 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' );
var Float32Array = require( '@stdlib/array/float32' );
var Complex64Array = require( '@stdlib/array/complex64' );
var reinterpretComplex64 = require( '@stdlib/strided/base/reinterpret-complex64' );
var cscal = require( '@stdlib/blas/base/cscal-wasm' );

// Create a new memory instance with an initial size of 10 pages (320KiB) and a maximum size of 100 pages (6.4MiB):
var mem = new Memory({
    'initial': 10,
    'maximum': 100
});

// Create a BLAS routine:
var mod = new cscal.Module( mem );
// returns <Module>

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

// Define a vector data type:
var dtype = 'complex64';

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

// Define a pointer (i.e., byte offset) for storing the input vector:
var xptr = 0;

// Define a pointer for storing a complex number:
var zptr = N * bytesPerElement( dtype );

// Write vector values to module memory:
var xbuf = oneTo( N*2, 'float32' );
var x = new Complex64Array( xbuf.buffer );
mod.write( xptr, x );

// Write a complex number to module memory:
mod.write( zptr, new Float32Array( [ 2.0, 2.0 ] ) );

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

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

console.log( reinterpretComplex64( view, 0 ) );
// => <Float32Array>[ -2.0, 6.0, -2.0, 14.0, -2.0, 22.0, -2.0, 30.0, -2.0, 38.0 ]

The function has the following additional parameters:

  • ox: starting index for x.

Notes

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

Examples

var hasWebAssemblySupport = require( '@stdlib/assert/has-wasm-support' );
var oneTo = require( '@stdlib/array/one-to' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );
var Complex64Array = require( '@stdlib/array/complex64' );
var reinterpretComplex64 = require( '@stdlib/strided/base/reinterpret-complex64' );
var cscal = require( '@stdlib/blas/base/cscal-wasm' );

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

// Create an input array:
var xbuf = oneTo( N*2, 'float32' );
var x = new Complex64Array( xbuf.buffer );

// Create a complex number:
var z = new Complex64( 2.0, 2.0 );

// Perform computation:
cscal.ndarray( N, z, x, 1, 0 );

// Print the results:
console.log( reinterpretComplex64( x, 0 ) );
// => <Float32Array>[ -2.0, 6.0, -2.0, 14.0, -2.0, 22.0, -2.0, 30.0, -2.0, 38.0 ]
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