sapx
Add a constant to each element in a single-precision floating-point strided array.
Usage
var sapx = require( '@stdlib/blas/ext/base/sapx' );
sapx( N, alpha, x, stride )
Adds a constant alpha
to each element in a single-precision floating-point strided array x
.
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
sapx( x.length, 5.0, x, 1 );
// x => <Float32Array>[ 3.0, 6.0, 8.0, 0.0, 9.0, 5.0, 4.0, 2.0 ]
The function has the following parameters:
- N: number of indexed elements.
- alpha: scalar constant.
- x: input
Float32Array
. - stride: index increment.
The N
and stride
parameters determine which elements in x
are accessed at runtime. For example, to add a constant to every other element
var Float32Array = require( '@stdlib/array/float32' );
var floor = require( '@stdlib/math/base/special/floor' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
var N = floor( x.length / 2 );
sapx( N, 5.0, x, 2 );
// x => <Float32Array>[ 3.0, 1.0, 8.0, -5.0, 9.0, 0.0, 4.0, -3.0 ]
Note that indexing is relative to the first index. To introduce an offset, use typed array
views.
var Float32Array = require( '@stdlib/array/float32' );
var floor = require( '@stdlib/math/base/special/floor' );
// Initial array...
var x0 = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
// Create an offset view...
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var N = floor( x0.length/2 );
// Add a constant to every other element...
sapx( N, 5.0, x1, 2 );
// x0 => <Float32Array>[ 1.0, 3.0, 3.0, 1.0, 5.0, -1.0 ]
sapx.ndarray( N, alpha, x, stride, offset )
Adds a constant alpha
to each element in a single-precision floating-point strided array x
using alternative indexing semantics.
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
sapx.ndarray( x.length, 5.0, x, 1, 0 );
// x => <Float32Array>[ 3.0, 6.0, 8.0, 0.0, 9.0, 5.0, 4.0, 2.0 ]
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 Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
sapx.ndarray( 3, 5.0, x, 1, x.length-3 );
// x => <Float32Array>[ 1.0, -2.0, 3.0, 1.0, 10.0, -1.0 ]
Notes
- If
N <= 0
, both functions returnx
unchanged.
Examples
var round = require( '@stdlib/math/base/special/round' );
var randu = require( '@stdlib/random/base/randu' );
var Float32Array = require( '@stdlib/array/float32' );
var sapx = require( '@stdlib/blas/ext/base/sapx' );
var rand;
var sign;
var x;
var i;
x = new Float32Array( 10 );
for ( i = 0; i < x.length; i++ ) {
rand = round( randu()*100.0 );
sign = randu();
if ( sign < 0.5 ) {
sign = -1.0;
} else {
sign = 1.0;
}
x[ i ] = sign * rand;
}
console.log( x );
sapx( x.length, 5.0, x, 1 );
console.log( x );