dmap
Apply a unary function to a double-precision floating-point strided input array and assign results to a double-precision floating-point strided output array.
Usage
var dmap = require( '@stdlib/strided/base/dmap' );
dmap( N, x, strideX, y, strideY, fcn )
Applies a unary function to a double-precision floating-point strided input array and assigns results to a double-precision floating-point strided output array.
var Float64Array = require( '@stdlib/array/float64' );
var abs = require( '@stdlib/math/base/special/abs' );
var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
// Compute the absolute values in-place:
dmap( x.length, x, 1, x, 1, abs );
// x => <Float64Array>[ 2.0, 1.0, 3.0, 5.0, 4.0, 0.0, 1.0, 3.0 ]
The function accepts the following arguments:
- N: number of indexed elements.
- x: input
Float64Array. - strideX: index increment for
x. - y: output
Float64Array. - strideY: index increment for
y. - fcn: function to apply.
The N and stride parameters determine which elements in x and y 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 abs = require( '@stdlib/math/base/special/abs' );
var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
dmap( 3, x, 2, y, -1, abs );
// y => <Float64Array>[ 5.0, 3.0, 1.0, 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 abs = require( '@stdlib/math/base/special/abs' );
// Initial arrays...
var x0 = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y0 = 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
dmap( 3, x1, -2, y1, 1, abs );
// y0 => <Float64Array>[ 0.0, 0.0, 0.0, 6.0, 4.0, 2.0 ]
dmap.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, fcn )
Applies a unary function to a double-precision floating-point strided input array and assigns results to a double-precision floating-point strided output array using alternative indexing semantics.
var Float64Array = require( '@stdlib/array/float64' );
var abs = require( '@stdlib/math/base/special/abs' );
var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0 ] );
var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );
dmap.ndarray( x.length, x, 1, 0, y, 1, 0, abs );
// y => <Float64Array>[ 1.0, 2.0, 3.0, 4.0, 5.0 ]
The function accepts the following additional arguments:
- offsetX: starting index for
x. - offsetY: starting index for
y.
While typed array views mandate a view offset based on the underlying buffer, the offsetX and offsetY 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 abs = require( '@stdlib/math/base/special/abs' );
var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
dmap.ndarray( 3, x, 2, 1, y, -1, y.length-1, abs );
// y => <Float64Array>[ 0.0, 0.0, 0.0, 6.0, 4.0, 2.0 ]
Examples
var round = require( '@stdlib/math/base/special/round' );
var randu = require( '@stdlib/random/base/randu' );
var Float64Array = require( '@stdlib/array/float64' );
var dmap = require( '@stdlib/strided/base/dmap' );
function scale( x ) {
return x * 10.0;
}
var x = new Float64Array( 10 );
var y = new Float64Array( 10 );
var i;
for ( i = 0; i < x.length; i++ ) {
x[ i ] = round( (randu()*200.0) - 100.0 );
}
console.log( x );
console.log( y );
dmap.ndarray( x.length, x, 1, 0, y, -1, y.length-1, scale );
console.log( y );
C APIs
Usage
#include "stdlib/strided/base/dmap.h"
stdlib_strided_dmap( N, *X, strideX, *Y, strideY, fcn )
Applies a unary function to a double-precision floating-point strided input array and assigns results to a double-precision floating-point strided output array.
#include <stdint.h>
static double scale( const double x ) {
return x * 10.0;
}
double X[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };
double Y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
int64_t N = 6;
stdlib_strided_dmap( N, X, 1, Y, 1, scale );
The function accepts the following arguments:
- N:
[in] int64_tnumber of indexed elements. - X:
[in] double*input array. - strideX
[in] int64_tindex increment forX. - Y:
[out] double*output array. - strideY:
[in] int64_tindex increment forY. - fcn:
[in] double (*fcn)( double )unary function to apply.
void stdlib_strided_dmap( const int64_t N, const double *X, const int64_t strideX, double *Y, const int64_t strideY, double (*fcn)( double ) );
Examples
#include "stdlib/strided/base/dmap.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>
// Define a callback:
static double scale( const double x ) {
return x * 10.0;
}
int main( void ) {
// Create an input strided array:
double X[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };
// Create an output strided array:
double Y[] = { 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;
// Apply the callback:
stdlib_strided_dmap( N, X, strideX, Y, strideY, scale );
// Print the results:
for ( int64_t i = 0; i < N; i++ ) {
printf( "Y[ %"PRId64" ] = %lf\n", i, Y[ i ] );
}
}