dapxsumpw

Add a scalar constant to each double-precision floating-point strided array element and compute the sum using pairwise summation.

Installation

npm install @stdlib/blas-ext-base-dapxsumpw

Usage

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

dapxsumpw( N, alpha, x, strideX )

Adds a scalar constant to each double-precision floating-point strided array element and computes the sum using pairwise summation.

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

var x = new Float64Array( [ 1.0, -2.0, 2.0 ] );

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

The function has the following parameters:

• N: number of indexed elements.
• x: input Float64Array.
• 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 Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );

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

var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var v = dapxsumpw( 4, 5.0, x1, 2 );
// returns 25.0

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

Adds a scalar constant to each double-precision floating-point strided array element and computes the sum using pairwise summation and alternative indexing semantics.

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

var x = new Float64Array( [ 1.0, -2.0, 2.0 ] );

var v = dapxsumpw.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 Float64Array = require( '@stdlib/array-float64' );

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

var v = dapxsumpw.ndarray( 4, 5.0, x, 2, 1 );
// returns 25.0

Notes

• If N <= 0, both functions return 0.0.

Examples

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

var x = discreteUniform( 10, -100, 100, {
    'dtype': 'float64'
});
console.log( x );

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

C APIs

Usage

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

stdlib_strided_dapxsumpw( N, alpha, *X, strideX )

Adds a scalar constant to each double-precision floating-point strided array element and computes the sum using pairwise summation.

const double x[] = { 1.0, 2.0, 3.0, 4.0 };

double v = stdlib_strided_dapxsumpw( 4, 5.0, x, 1 );
// returns 30.0

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• alpha: [in] double scalar constant.
• X: [in] double* input array.
• strideX: [in] CBLAS_INT stride length for X.

double stdlib_strided_dapxsumpw( const CBLAS_INT N, const double alpha, const double *X, const CBLAS_INT strideX );

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

Adds a scalar constant to each double-precision floating-point strided array element and computes the sum using pairwise summation and alternative indexing semantics.

const double x[] = { 1.0, 2.0, 3.0, 4.0 };

double v = stdlib_strided_dapxsumpw_ndarray( 4, 5.0, x, 1, 0 );
// returns 30.0

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• alpha: [in] double scalar constant.
• X: [in] double* input array.
• strideX: [in] CBLAS_INT stride length for X.
• offsetX: [in] CBLAS_INT starting index for X.

double stdlib_strided_dapxsumpw_ndarray( const CBLAS_INT N, const double alpha, const double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

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

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

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

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

    // Compute the sum:
    double v = stdlib_strided_dapxsumpw( N, 5.0, 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/dapxsum: add a scalar constant to each double-precision floating-point strided array element and compute the sum.
• @stdlib/blas-ext/base/dsumpw: calculate the sum of double-precision floating-point strided array elements using pairwise summation.
• @stdlib/blas-ext/base/gapxsumpw: add a scalar constant to each strided array element and compute the sum using pairwise summation.
• @stdlib/blas-ext/base/sapxsumpw: add a scalar constant to each single-precision floating-point strided array element and compute the sum using pairwise summation.

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.