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dfill

Fill a double-precision floating-point strided array with a specified scalar constant.

Usage

var dfill = require( '@stdlib/blas/ext/base/dfill' );

dfill( N, alpha, x, stride )

Fills a double-precision floating-point strided array x with a specified scalar constant alpha.

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

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

dfill( x.length, 5.0, x, 1 );
// x => <Float64Array>[ 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0 ]

The function has the following parameters:

  • N: number of indexed elements.
  • alpha: scalar constant.
  • x: input Float64Array.
  • stride: index increment.

The N and stride parameters determine which elements in the strided array are accessed at runtime. For example, to fill every other element

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

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

dfill( 4, 5.0, x, 2 );
// x => <Float64Array>[ 5.0, 1.0, 5.0, -5.0, 5.0, 0.0, 5.0, -3.0 ]

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

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

// Initial array...
var x0 = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );

// Create an offset view...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Fill every other element...
dfill( 3, 5.0, x1, 2 );
// x0 => <Float64Array>[ 1.0, 5.0, 3.0, 5.0, 5.0, 5.0 ]

dfill.ndarray( N, alpha, x, stride, offset )

Fills a double-precision floating-point strided array x with a specified scalar constant alpha using alternative indexing semantics.

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

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

dfill.ndarray( x.length, 5.0, x, 1, 0 );
// x => <Float64Array>[ 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0 ]

The function has the following additional parameters:

  • offset: starting index.

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 access only the last three elements of x

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

var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );

dfill.ndarray( 3, 5.0, x, 1, x.length-3 );
// x => <Float64Array>[ 1.0, -2.0, 3.0, 5.0, 5.0, 5.0 ]

Notes

  • If N <= 0, both functions return x unchanged.

Examples

var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var filledarrayBy = require( '@stdlib/array/filled-by' );
var dfill = require( '@stdlib/blas/ext/base/dfill' );

var rand = discreteUniform( -100, 100 );

var x = filledarrayBy( 10, 'float64', rand );
console.log( x );

dfill( x.length, 5.0, x, 1 );
console.log( x );

See Also