smskmap2

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

Usage

var smskmap2 = require( '@stdlib/strided/base/smskmap2' );

smskmap2( N, x, strideX, y, strideY, mask, strideMask, z, strideZ, fcn )

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

var Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );
var addf = require( '@stdlib/math/base/ops/addf' );

var x = new Float32Array( [ -2.0, 1.0, -3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
var y = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var z = new Float32Array( x.length );
var m = new Uint8Array( [ 0, 0, 1, 0, 0, 1, 1, 0 ] );

smskmap2( x.length, x, 1, y, 1, m, 1, z, 1, addf );
// z => <Float32Array>[ -1.0, 3.0, 0.0, -1.0, 9.0, 0.0, 0.0, 5.0 ]

The function accepts the following arguments:

  • N: number of indexed elements.
  • x: input Float32Array.
  • strideX: index increment for x.
  • y: input Float32Array.
  • strideY: index increment for y.
  • mask: mask Uint8Array.
  • strideMask: index increment for mask.
  • z: output Float32Array.
  • strideZ: index increment for z.
  • fcn: function to apply.

The N and stride parameters determine which elements in the strided arrays 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 Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );
var addf = require( '@stdlib/math/base/ops/addf' );

var x = new Float32Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y = new Float32Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
var z = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var m = new Uint8Array( [ 0, 0, 1, 0, 0, 1 ] );

smskmap2( 3, x, 2, y, -1, m, 2, z, 1, addf );
// z => <Float32Array>[ 1.0, 0.0, -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 Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );
var addf = require( '@stdlib/math/base/ops/addf' );

// Initial arrays...
var x0 = new Float32Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y0 = new Float32Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
var z0 = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var m0 = new Uint8Array( [ 0, 0, 1, 0, 0, 1 ] );

// Create offset views...
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float32Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element
var z1 = new Float32Array( z0.buffer, z0.BYTES_PER_ELEMENT*2 ); // start at 3rd element
var m1 = new Uint8Array( m0.buffer, m0.BYTES_PER_ELEMENT*3 ); // start at 4th element

smskmap2( 3, x1, -2, y1, 1, m1, 1, z1, 1, addf );
// z0 => <Float32Array>[ 0.0, 0.0, -4.0, -1.0, 0.0, 0.0 ]

smskmap2.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, mask, strideMask, offsetMask, z, strideZ, offsetZ, fcn )

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

var Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );
var addf = require( '@stdlib/math/base/ops/addf' );

var x = new Float32Array( [ -1.0, -2.0, -3.0, -4.0, -5.0 ] );
var y = new Float32Array( [ 1.0, 1.0, 2.0, 2.0, 3.0 ] );
var z = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var m = new Uint8Array( [ 0, 0, 1, 0, 0 ] );

smskmap2.ndarray( x.length, x, 1, 0, y, 1, 0, m, 1, 0, z, 1, 0, addf );
// z => <Float32Array>[ 0.0, -1.0, 0.0, -2.0, -2.0 ]

The function accepts the following addfitional arguments:

  • offsetX: starting index for x.
  • offsetY: starting index for y.
  • offsetMask: starting index for mask.
  • 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 Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );
var addf = require( '@stdlib/math/base/ops/addf' );

var x = new Float32Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y = new Float32Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
var z = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var m = new Uint8Array( [ 0, 0, 1, 0, 0, 1 ] );

smskmap2.ndarray( 3, x, 2, 1, y, -1, y.length-1, m, 2, 1, z, 1, 0, addf );
// z => <Float32Array>[ 1.0, -1.0, 0.0, 0.0, 0.0, 0.0 ]

Examples

var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var bernoulli = require( '@stdlib/random/base/bernoulli' ).factory;
var Float32Array = require( '@stdlib/array/float32' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var addf = require( '@stdlib/math/base/ops/addf' );
var smskmap2 = require( '@stdlib/strided/base/smskmap2' );

var x = filledarrayBy( 10, 'float32', discreteUniform( -100, 100 ) );
console.log( x );

var y = filledarrayBy( x.length, 'float32', discreteUniform( -100, 100 ) );
console.log( y );

var m = filledarrayBy( x.length, 'uint8', bernoulli( 0.2 ) );
console.log( m );

var z = new Float32Array( x.length );
console.log( z );

smskmap2.ndarray( x.length, x, 1, 0, y, -1, y.length-1, m, 1, 0, z, 1, 0, addf );
console.log( z );

C APIs

Usage

#include "stdlib/strided/base/smskmap2.h"

stdlib_strided_smskmap2( N, *X, strideX, *Y, strideY, *Mask, strideMask, *Z, strideZ, fcn )

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

#include <stdint.h>

static float addf( const float x, const float y ) {
    return x + y;
}

float X[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
float Y[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
float Z[] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
uint8_t M[] = { 0, 0, 1, 0, 0, 1 };

int64_t N = 6;

stdlib_strided_smskmap2( N, X, 1, Y, 1, M, 1, Z, 1, addf );

The function accepts the following arguments:

  • N: [in] int64_t number of indexed elements.
  • X: [in] float* input array.
  • strideX [in] int64_t index increment for X.
  • Y: [int] float* input array.
  • strideY: [in] int64_t index increment for Y.
  • Mask: [in] uint8_t* mask array.
  • strideMask: [in] int64_t index increment for Mask.
  • Z: [out] float* output array.
  • strideZ: [in] int64_t index increment for Z.
  • fcn: [in] float (*fcn)( float, float ) binary function to apply.
void stdlib_strided_smskmap2( const int64_t N, const float *X, const int64_t strideX, const float *Y, const int64_t strideY, const uint8_t *Mask, const int64_t strideMask, float *Z, const int64_t strideZ, float (*fcn)( float, float ) );

Examples

#include "stdlib/strided/base/smskmap2.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>

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

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

    // Create a mask strided array:
    uint8_t M[] = { 0, 0, 1, 0, 0, 1 };

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

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

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

    // Apply the callback:
    stdlib_strided_smskmap2( N, X, strideX, Y, strideY, M, strideM, Z, strideZ, addf );

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

See Also

  • @stdlib/strided/base/dmskmap2: apply a binary function to double-precision floating-point strided input arrays according to a strided mask array and assign results to a double-precision floating-point strided output array.
  • @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/smskmap: apply a unary function to a single-precision floating-point strided input array according to a strided mask array and assign results to a single-precision floating-point strided output array.
Did you find this page helpful?