sdsapxsum
Add a constant to each single-precision floating-point strided array element and compute the sum using extended accumulation.
Usage
var sdsapxsum = require( '@stdlib/blas/ext/base/sdsapxsum' );
sdsapxsum( N, alpha, x, stride )
Adds a constant to each single-precision floating-point strided array element and computes the sum using extended accumulation.
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, -2.0, 2.0 ] );
var v = sdsapxsum( 3, 5.0, x, 1 );
// returns 16.0
The function has the following parameters:
- N: number of indexed elements.
- x: input
Float32Array
. - stride: index increment for
x
.
The N
and stride
parameters determine which elements in the strided array are accessed at runtime. For example, to access every other element in the strided array,
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );
var v = sdsapxsum( 4, 5.0, x, 2 );
// returns 25.0
Note that indexing is relative to the first index. To introduce an offset, use typed array
views.
var Float32Array = require( '@stdlib/array/float32' );
var x0 = new Float32Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var v = sdsapxsum( 4, 5.0, x1, 2 );
// returns 25.0
sdsapxsum.ndarray( N, alpha, x, stride, offset )
Adds a constant to each single-precision floating-point strided array element and computes the sum using extended accumulation and alternative indexing semantics.
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, -2.0, 2.0 ] );
var v = sdsapxsum.ndarray( 3, 5.0, x, 1, 0 );
// returns 16.0
The function has the following additional parameters:
- offset: starting index for
x
.
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 every other value in the strided array starting from the second value
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var v = sdsapxsum.ndarray( 4, 5.0, x, 2, 1 );
// returns 25.0
Notes
- If
N <= 0
, both functions return0.0
. - Accumulated intermediate values are stored as double-precision floating-point numbers.
Examples
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var filledarrayBy = require( '@stdlib/array/filled-by' );
var sdsapxsum = require( '@stdlib/blas/ext/base/sdsapxsum' );
var x = filledarrayBy( 10, 'float32', discreteUniform( 0, 100 ) );
console.log( x );
var v = sdsapxsum( x.length, 5.0, x, 1 );
console.log( v );