dmap2

Apply a binary function to double-precision floating-point strided input arrays and assign results to a double-precision floating-point strided output array.

Usage

var dmap2 = require( '@stdlib/strided/base/dmap2' );

dmap2( N, x, strideX, y, strideY, z, strideZ, fcn )

Applies a binary function to double-precision floating-point strided input arrays and assigns results to a double-precision floating-point strided output array.

var Float64Array = require( '@stdlib/array/float64' );
var add = require( '@stdlib/math/base/ops/add' );

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
var y = new Float64Array( [ 2.0, 1.0, 3.0, -2.0, 4.0, 1.0, -1.0, 3.0 ] );
var z = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dmap2( x.length, x, 1, y, 1, z, 1, add );
// z => <Float64Array>[ 0.0, 2.0, 6.0, -7.0, 8.0, 1.0, -2.0, 0.0 ]

The function accepts the following arguments:

  • N: number of indexed elements.
  • x: input Float64Array.
  • strideX: index increment for x.
  • y: input Float64Array.
  • strideY: index increment for y.
  • z: output Float64Array.
  • strideZ: index increment for z.
  • fcn: function to apply.

The N and stride parameters determine which strided array elements are accessed at runtime. For example, to index every other value in x and to index the first N elements of y in reverse order,

var Float64Array = require( '@stdlib/array/float64' );
var add = require( '@stdlib/math/base/ops/add' );

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y = new Float64Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
var z = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dmap2( 3, x, 2, y, -1, z, 1, add );
// z => <Float64Array>[ 1.0, -2.0, -4.0, 0.0, 0.0, 0.0 ]

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

var Float64Array = require( '@stdlib/array/float64' );
var add = require( '@stdlib/math/base/ops/add' );

// Initial arrays...
var x0 = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y0 = new Float64Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
var z0 = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element
var z1 = new Float64Array( z0.buffer, z0.BYTES_PER_ELEMENT*2 ); // start at 3rd element

dmap2( 3, x1, -2, y1, 1, z1, 1, add );
// z0 => <Float64Array>[ 0.0, 0.0, -4.0, -1.0, 1.0, 0.0 ]

dmap2.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, z, strideZ, offsetZ, fcn )

Applies a binary function to double-precision floating-point strided input arrays and assigns results to a double-precision floating-point strided output array using alternative indexing semantics.

var Float64Array = require( '@stdlib/array/float64' );
var add = require( '@stdlib/math/base/ops/add' );

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0 ] );
var y = new Float64Array( [ 1.0, 1.0, 2.0, 2.0, 3.0 ] );
var z = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dmap2.ndarray( x.length, x, 1, 0, y, 1, 0, z, 1, 0, add );
// z => <Float64Array>[ 0.0, -1.0, -1.0, -2.0, -2.0 ]

The function accepts the following additional arguments:

  • offsetX: starting index for x.
  • offsetY: starting index for y.
  • offsetZ: starting index for z.

While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to index every other value in x starting from the second value and to index the last N elements in y in reverse order,

var Float64Array = require( '@stdlib/array/float64' );
var add = require( '@stdlib/math/base/ops/add' );

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y = new Float64Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
var z = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dmap2.ndarray( 3, x, 2, 1, y, -1, y.length-1, z, 1, 3, add );
// z => <Float64Array>[ 0.0, 0.0, 0.0, 1.0, -1.0, -4.0 ]

Examples

var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var filledarrayBy = require( '@stdlib/array/filled-by' );
var Float64Array = require( '@stdlib/array/float64' );
var add = require( '@stdlib/math/base/ops/add' );
var dmap2 = require( '@stdlib/strided/base/dmap2' );

var x = filledarrayBy( 10, 'float64', discreteUniform( -100, 100 ) );
console.log( x );

var y = filledarrayBy( x.length, 'float64', discreteUniform( -100, 100 ) );
console.log( y );

var z = new Float64Array( x.length );
console.log( z );

dmap2.ndarray( x.length, x, 1, 0, y, -1, y.length-1, z, 1, 0, add );
console.log( z );

C APIs

Usage

#include "stdlib/strided/base/dmap2.h"

stdlib_strided_dmap2( N, *X, strideX, *Y, strideY, *Z, strideZ, fcn )

Applies a binary function to double-precision floating-point strided input arrays and assigns results to a double-precision floating-point strided output array.

#include <stdint.h>

static double add( const double x, const double y ) {
    return x + y;
}

double X[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };
double Y[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };
double Z[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };

int64_t N = 6;

stdlib_strided_dmap2( N, X, 1, Y, 1, Z, 1, add );

The function accepts the following arguments:

  • N: [in] int64_t number of indexed elements.
  • X: [in] double* input array.
  • strideX [in] int64_t index increment for X.
  • Y: [in] double* input array.
  • strideY: [in] int64_t index increment for Y.
  • Z: [out] double* output array.
  • strideZ: [in] int64_t index increment for Z.
  • fcn: [in] double (*fcn)( double, double ) binary function to apply.
void stdlib_strided_dmap2( const int64_t N, const double *X, const int64_t strideX, const double *Y, const int64_t strideY, double *Z, const int64_t strideZ, double (*fcn)( double, double ) );

Examples

#include "stdlib/strided/base/dmap2.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>

// Define a callback:
static double add( const double x, const double y ) {
    return x + y;
}

int main( void ) {
    // Create input strided arrays:
    double X[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };
    double Y[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };

    // Create an output strided array:
    double Z[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };

    // Specify the number of elements:
    int64_t N = 6;

    // Define the strides:
    int64_t strideX = 1;
    int64_t strideY = -1;
    int64_t strideZ = 1;

    // Apply the callback:
    stdlib_strided_dmap2( N, X, strideX, Y, strideY, Z, strideZ, add );

    // Print the results:
    for ( int64_t i = 0; i < N; i++ ) {
        printf( "Z[ %"PRId64" ] = %lf\n", i, Z[ i ] );
    }
}

See Also

  • @stdlib/strided/base/smap2: apply a binary function to single-precision floating-point strided input arrays and assign results to a single-precision floating-point strided output array.
  • @stdlib/strided/base/binary: apply a binary callback to elements in strided input arrays and assign results to elements in a strided output array.
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