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csum

README.md

csum

Calculate the sum of single-precision complex floating-point strided array elements.

Usage

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

csum( N, x, strideX )

Computes the sum of single-precision complex floating-point strided array elements.

var Complex64Array = require( '@stdlib/array/complex64' );

var x = new Complex64Array( [ 1.0, -2.0, 2.0, 3.0 ] );

var v = csum( x.length, x, 1 );
// returns <Complex64>[ 3.0, 1.0 ]

The function has the following parameters:

  • N: number of indexed elements.
  • x: input Complex64Array.
  • strideX: stride length for x.

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

var Complex64Array = require( '@stdlib/array/complex64' );

var x = new Complex64Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );

var v = csum( 2, x, 2 );
// returns <Complex64>[ -1.0, 5.0 ]

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

var Complex64Array = require( '@stdlib/array/complex64' );

var x0 = new Complex64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Complex64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var v = csum( 2, x1, 2 );
// returns <Complex64>[ 5.0, 2.0 ]

csum.ndarray( N, x, strideX, offsetX )

Computes the sum of single-precision complex floating-point strided array elements using alternative indexing semantics.

var Complex64Array = require( '@stdlib/array/complex64' );

var x = new Complex64Array( [ 1.0, -2.0, 2.0, 3.0 ] );

var v = csum.ndarray( 2, x, 1, 0 );
// returns <Complex64>[ 3.0, 1.0 ]

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 calculate the sum of every other element starting from the second element:

var Complex64Array = require( '@stdlib/array/complex64' );

var x = new Complex64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );

var v = csum.ndarray( 2, x, 2, 1 );
// returns <Complex64>[ 5.0, 2.0 ]

Notes

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

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var Complex64Array = require( '@stdlib/array/complex64' );
var csum = require( '@stdlib/blas/ext/base/csum' );

var xbuf = discreteUniform( 10, -100, 100, {
    'dtype': 'float32'
});
console.log( xbuf );

var x = new Complex64Array( xbuf );
var v = csum( x.length, x, 1 );
console.log( v );

C APIs

Usage

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

stdlib_strided_csum( N, *X, strideX )

Computes the sum of single-precision complex floating-point strided array elements.

#include "stdlib/complex/float32/ctor.h"

const stdlib_complex64_t x[] = {
    stdlib_complex64( 1.0f, 2.0f ),
    stdlib_complex64( 3.0f, 4.0f )
};

stdlib_complex64_t v = stdlib_strided_csum( 2, x, 1 );

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • X: [in] stdlib_complex64_t* input array.
  • strideX: [in] CBLAS_INT stride length for X.
stdlib_complex64_t stdlib_strided_csum( const CBLAS_INT N, const stdlib_complex64_t *X, const CBLAS_INT strideX );

stdlib_strided_csum_ndarray( N, *X, strideX, offsetX )

Computes the sum of single-precision complex floating-point strided array elements using alternative indexing semantics.

#include "stdlib/complex/float32/ctor.h"

const stdlib_complex64_t x[] = {
    stdlib_complex64( 1.0f, 2.0f ),
    stdlib_complex64( 3.0f, 4.0f )
};

stdlib_complex64_t v = stdlib_strided_csum_ndarray( 2, x, 1, 0 );

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • X: [in] stdlib_complex64_t* input array.
  • strideX: [in] CBLAS_INT stride length for X.
  • offsetX: [in] CBLAS_INT starting index for X.
stdlib_complex64_t stdlib_strided_csum_ndarray( const CBLAS_INT N, const stdlib_complex64_t *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

#include "stdlib/blas/ext/base/csum.h"
#include "stdlib/complex/float32/ctor.h"
#include "stdlib/complex/float32/real.h"
#include "stdlib/complex/float32/imag.h"
#include <stdio.h>

int main( void ) {
    // Create a strided array:
    const stdlib_complex64_t x[] = {
        stdlib_complex64( 1.0f, 2.0f ),
        stdlib_complex64( 3.0f, 4.0f ),
        stdlib_complex64( 5.0f, 6.0f ),
        stdlib_complex64( 7.0f, 8.0f )
    };

    // Specify the number of elements:
    const int N = 4;

    // Specify the stride length:
    const int strideX = 1;

    // Compute the sum:
    stdlib_complex64_t v = stdlib_strided_csum( N, x, strideX );

    // Print the result:
    printf( "sum: %f + %fi\n", stdlib_complex64_real( v ), stdlib_complex64_imag( v ) );
}