mul

Element-wise multiplication of two strided arrays.

Usage

var mul = require( '@stdlib/math/strided/ops/mul' );

mul( N, dtypeX, x, strideX, dtypeY, y, strideY, dtypeZ, z, strideZ )

Multiplies each element in a strided array x to a corresponding element in a strided array y and assigns the results to elements in a strided array z.

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

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0 ] );
var y = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var z = new Float64Array( x.length );

mul( x.length, 'float64', x, 1, 'float64', y, 1, 'float64', z, 1 );
// z => <Float64Array>[ -2.0, 2.0, 9.0, -20.0, 20.0 ]

The function accepts the following arguments:

N: number of indexed elements.
dtypeX: data type for x.
x: input array-like object.
strideX: index increment for x.
dtypeY: data type for y.
y: input array-like object.
strideY: index increment for y.
dtypeZ: data type for z.
z: output array-like object.
strideZ: index increment for z.

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

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

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0 ] );
var y = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var z = new Float64Array( x.length );

mul( 3, 'float64', x, 2, 'float64', y, -1, 'float64', z, 1 );
// z => <Float64Array>[ -6.0, 6.0, 4.0, 0.0, 0.0, 0.0 ]

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( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0 ] );
var y0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var z0 = new Float64Array( x0.length );

// 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
var z1 = new Float64Array( z0.buffer, z0.BYTES_PER_ELEMENT*2 ); // start at 3rd element

mul( 3, 'float64', x1, -2, 'float64', y1, 1, 'float64', z1, 1 );
// z0 => <Float64Array>[ 0.0, 0.0, 0.0, -25.0, 6.0, 0.0 ]

mul.ndarray( N, dtypeX, x, strideX, offsetX, dtypeY, y, strideY, offsetY, dtypeZ, z, strideZ, offsetZ )

Multiplies each element in a strided array x to a corresponding element in a strided array y and assigns the results to elements in a strided array z using alternative indexing semantics.

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

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0 ] );
var y = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var z = new Float64Array( x.length );

mul.ndarray( x.length, 'float64', x, 1, 0, 'float64', y, 1, 0, 'float64', z, 1, 0 );
// z => <Float64Array>[ -2.0, 2.0, 9.0, -20.0, 20.0 ]

The function accepts the following additional arguments:

offsetX: starting index for x.
offsetY: starting index for y.
offsetZ: starting index for z.

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 index every other value in x starting from the second value and to index the last N elements in y in reverse order,

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

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0 ] );
var y = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var z = new Float64Array( x.length );

mul.ndarray( 3, 'float64', x, 2, 1, 'float64', y, -1, y.length-1, 'float64', z, 1, 0 );
// z => <Float64Array>[ 6.0, -25.0, 0.0, 0.0, 0.0, 0.0 ]

Examples

var uniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var filledarray = require( '@stdlib/array/filled' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var mul = require( '@stdlib/math/strided/ops/mul' );

var dt;
var x;
var y;
var z;
var i;

dt = [ 'float64', 'float32', 'int32', 'uint8', 'generic' ];

for ( i = 0; i < dt.length; i++ ) {
    x = filledarrayBy( 10, dt[ i ], uniform( 0.0, 10.0 ) );
    console.log( x );

    y = filledarrayBy( x.length, dt[ i ], uniform( 0.0, 10.0 ) );
    console.log( y );

    z = filledarray( 0.0, x.length, 'generic' );
    console.log( z );

    mul.ndarray( x.length, dt[ i ], x, 1, 0, dt[ i ], y, 1, 0, 'generic', z, -1, z.length-1 );
    console.log( z );
    console.log( '' );
}