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dsort

README.md

dsort

Sort a double-precision floating-point strided array.

Usage

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

dsort( N, order, x, strideX )

Sorts a double-precision floating-point strided array.

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

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

dsort( x.length, 1.0, x, 1 );
// x => <Float64Array>[ -4.0, -2.0, 1.0, 3.0 ]

The function has the following parameters:

  • N: number of indexed elements.
  • order: sort order. If order < 0.0, the input strided array is sorted in decreasing order. If order > 0.0, the input strided array is sorted in increasing order. If order == 0.0, the input strided array is left unchanged.
  • x: input Float64Array.
  • strideX: stride length.

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

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

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

dsort( 2, -1.0, x, 2 );
// x => <Float64Array>[ 3.0, -2.0, 1.0, -4.0 ]

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

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

// Initial array...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );

// Create an offset view...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Sort every other element...
dsort( 2, -1.0, x1, 2 );
// x0 => <Float64Array>[ 1.0, 4.0, 3.0, 2.0 ]

dsort.ndarray( N, order, x, strideX, offsetX )

Sorts a double-precision floating-point strided array using alternative indexing semantics.

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

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

dsort.ndarray( x.length, 1.0, x, 1, 0 );
// x => <Float64Array>[ -4.0, -2.0, 1.0, 3.0 ]

The function has the following additional parameters:

  • offsetX: 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:

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

var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );

dsort.ndarray( 3, 1.0, x, 1, 3 );
// x => <Float64Array>[ 1.0, -2.0, 3.0, -6.0, -4.0, 5.0 ]

Notes

  • If N <= 0 or order == 0.0, both functions return x unchanged.
  • The algorithm distinguishes between -0 and +0. When sorted in increasing order, -0 is sorted before +0. When sorted in decreasing order, -0 is sorted after +0.
  • The algorithm sorts NaN values to the end. When sorted in increasing order, NaN values are sorted last. When sorted in decreasing order, NaN values are sorted first.
  • The input strided array is sorted in-place (i.e., the input strided array is mutated).

Examples

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

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

dsort( x.length, 1.0, x, 1 );
console.log( x );

C APIs

Usage

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

stdlib_strided_dsort( N, order, *X, strideX )

Sorts a double-precision floating-point strided array.

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

stdlib_strided_dsort( 4, 1.0, x, 1 );

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • order: [in] double sort order. If order < 0.0, the input strided array is sorted in decreasing order. If order > 0.0, the input strided array is sorted in increasing order. If order == 0.0, the input strided array is left unchanged.
  • X: [inout] double* input array.
  • strideX: [in] CBLAS_INT stride length for X.
void stdlib_strided_dsort( const CBLAS_INT N, const double order, double *X, const CBLAS_INT strideX );

stdlib_strided_dsort_ndarray( N, order, *X, strideX, offsetX )

Sorts a double-precision floating-point strided array using alternative indexing semantics.

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

stdlib_strided_dsort_ndarray( 4, 1.0, x, 1, 0 );

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • order: [in] double sort order. If order < 0.0, the input strided array is sorted in decreasing order. If order > 0.0, the input strided array is sorted in increasing order. If order == 0.0, the input strided array is left unchanged.
  • X: [inout] double* input array.
  • strideX: [in] CBLAS_INT stride length for X.
  • offsetX: [in] CBLAS_INT starting index for X.
void stdlib_strided_dsort_ndarray( const CBLAS_INT N, const double order, double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

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

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

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

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

    // Sort the array:
    stdlib_strided_dsort( N, 1.0, x, strideX );

    // Print the result:
    for ( int i = 0; i < 8; i++ ) {
        printf( "x[ %i ] = %lf\n", i, x[ i ] );
    }
}