dsapxsumpw

Add a constant to each single-precision floating-point strided array element, and compute the sum using pairwise summation with extended accumulation and returning an extended precision result.

Usage

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

dsapxsumpw( N, alpha, x, strideX )

Adds a constant to each single-precision floating-point strided array element, and computes the sum using pairwise summation with extended accumulation and returning an extended precision result.

var Float32Array = require( '@stdlib/array/float32' );

var x = new Float32Array( [ 1.0, -2.0, 2.0 ] );

var v = dsapxsumpw( x.length, 5.0, x, 1 );
// returns 16.0

The function has the following parameters:

  • N: number of indexed elements.
  • alpha: scalar constant.
  • x: input Float32Array.
  • strideX: stride length 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:

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 = dsapxsumpw( 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 = dsapxsumpw( 4, 5.0, x1, 2 );
// returns 25.0

dsapxsumpw.ndarray( N, alpha, x, strideX, offsetX )

Adds a constant to each single-precision floating-point strided array element, and computes the sum using pairwise summation with extended accumulation and alternative indexing semantics and returning an extended precision result.

var Float32Array = require( '@stdlib/array/float32' );

var x = new Float32Array( [ 1.0, -2.0, 2.0 ] );

var v = dsapxsumpw.ndarray( x.length, 5.0, x, 1, 0 );
// returns 16.0

The function has the following additional parameters:

  • offsetX: 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 element starting from the second element:

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 = dsapxsumpw.ndarray( 4, 5.0, x, 2, 1 );
// returns 25.0

Notes

  • If N <= 0, both functions return 0.0.
  • Accumulated intermediate values are stored as double-precision floating-point numbers.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var dsapxsumpw = require( '@stdlib/blas/ext/base/dsapxsumpw' );

var x = discreteUniform( 10.0, -100, 100, {
    'dtype': 'float32'
});
console.log( x );

var v = dsapxsumpw( x.length, 5.0, x, 1 );
console.log( v );

C APIs

Usage

#include "stdlib/blas/ext/base/dsapxsumpw.h"

stdlib_strided_dsapxsumpw( N, alpha, *X, strideX )

Adds a constant to each single-precision floating-point strided array element, and computes the sum using pairwise summation with extended accumulation and returning an extended precision result.

const float x[] = { 1.0f, -2.0f, 2.0f };

double v = stdlib_strided_dsapxsumpw( 3, 5.0f, x, 1 );
// returns 16.0

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • alpha: [in] float scalar constant.
  • X: [in] float* input array.
  • strideX: [in] CBLAS_INT stride length for X.
double stdlib_strided_dsapxsumpw( const CBLAS_INT N, const float alpha, const float *X, const CBLAS_INT strideX );

stdlib_strided_dsapxsumpw_ndarray( N, alpha, *X, strideX, offsetX )

Adds a constant to each single-precision floating-point strided array element, and computes the sum using pairwise summation with extended accumulation and alternative indexing semantics and returning an extended precision result.

const float x[] = { 1.0f, -2.0f, 2.0f };

double v = stdlib_strided_dsapxsumpw_ndarray( 3, 5.0f, x, 1, 0 );
// returns 16.0

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • alpha: [in] float scalar constant.
  • X: [in] float* input array.
  • strideX: [in] CBLAS_INT stride length for X.
  • offsetX: [in] CBLAS_INT starting index for X.
double stdlib_strided_dsapxsumpw_ndarray( const CBLAS_INT N, const float alpha, const float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

#include "stdlib/blas/ext/base/dsapxsumpw.h"
#include <stdio.h>

int main( void ) {
    // Create a strided array:
    const float x[] = { 1.0f, -2.0f, 3.0f, -4.0f, 5.0f, -6.0f, 7.0f, -8.0f };

    // Specify the number of indexed elements:
    const int N = 8;

    // Specify a stride:
    const int strideX = 1;

    // Compute the sum:
    double v = stdlib_strided_dsapxsumpw( N, 5.0f, x, strideX );

    // Print the result:
    printf( "sum: %lf\n", v );
}

References

  • Higham, Nicholas J. 1993. "The Accuracy of Floating Point Summation." SIAM Journal on Scientific Computing 14 (4): 783–99. doi:10.1137/0914050.

See Also

  • @stdlib/blas/ext/base/dapxsumpw: adds a constant to each double-precision floating-point strided array element and computes the sum using pairwise summation.
  • @stdlib/blas/ext/base/dsapxsum: adds a constant to each single-precision floating-point strided array element and computes the sum using extended accumulation and returning an extended precision result.
  • @stdlib/blas/ext/base/dssumpw: calculate the sum of single-precision floating-point strided array elements using pairwise summation with extended accumulation and returning an extended precision result.
  • @stdlib/blas/ext/base/sapxsumpw: adds a constant to each single-precision floating-point strided array element and computes the sum using pairwise summation.
Did you find this page helpful?