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Add strided utility to apply a binary function to single-precision floating-point strided arrays
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‎lib/node_modules/@stdlib/strided/base/smap2/README.md

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<!--
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@license Apache-2.0
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Copyright (c) 2021 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<!-- lint disable maximum-heading-length -->
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# smap2
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> Apply a binary function accepting and returning single-precision floating-point numbers to corresponding elements in two single-precision floating-point strided input arrays and assign each result to an element in a single-precision floating-point strided output array.
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<section class="intro">
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</section>
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<!-- /.intro -->
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<section class="usage">
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## Usage
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```javascript
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var smap2 = require( '@stdlib/strided/base/smap2' );
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```
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#### smap2( N, x, strideX, y, strideY, z, strideZ, fcn )
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Applies a binary function accepting and returning single-precision floating-point numbers to corresponding elements in two single-precision floating-point strided input arrays and assigns each result to an element in a single-precision floating-point strided output array.
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```javascript
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var Float32Array = require( '@stdlib/array/float32' );
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var addf = require( '@stdlib/math/base/ops/addf' );
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var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
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var y = new Float32Array( [ 2.0, 1.0, 3.0, -2.0, 4.0, 1.0, -1.0, 3.0 ] );
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var z = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
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smap2( x.length, x, 1, y, 1, z, 1, addf );
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// z => <Float32Array>[ 0.0, 2.0, 6.0, -7.0, 8.0, 1.0, -2.0, 0.0 ]
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```
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The function accepts the following arguments:
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- **N**: number of indexed elements.
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- **x**: input [`Float32Array`][@stdlib/array/float32].
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- **strideX**: index increment for `x`.
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- **y**: input [`Float32Array`][@stdlib/array/float32].
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- **strideY**: index increment for `y`.
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- **z**: output [`Float32Array`][@stdlib/array/float32].
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- **strideZ**: index increment for `z`.
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- **fcn**: function to apply.
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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,
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```javascript
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var Float32Array = require( '@stdlib/array/float32' );
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var addf = require( '@stdlib/math/base/ops/addf' );
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var x = new Float32Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
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var y = new Float32Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
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var z = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
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smap2( 3, x, 2, y, -1, z, 1, addf );
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// z => <Float32Array>[ 2.0, 0.0, -3.0, 0.0, 0.0, 0.0 ]
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```
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Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][@stdlib/array/float32] views.
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```javascript
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var Float32Array = require( '@stdlib/array/float32' );
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var addf = require( '@stdlib/math/base/ops/addf' );
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// Initial arrays...
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var x0 = new Float32Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
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var y0 = new Float32Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
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var z0 = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
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// Create offset views...
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var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
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var y1 = new Float32Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element
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var z1 = new Float32Array( z0.buffer, z0.BYTES_PER_ELEMENT*2 ); // start at 3rd element
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smap2( 3, x1, -2, y1, 1, z1, 1, addf );
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// z0 => <Float32Array>[ 0.0, 0.0, -4.0, -1.0, 0.0, 0.0 ]
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```
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#### smap2.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, z, strideZ, offsetZ, fcn )
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Applies a binary function accepting and returning single-precision floating-point numbers to corresponding elements in two single-precision floating-point strided input arrays and assigns each result to an element in a single-precision floating-point strided output array using alternative indexing semantics.
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```javascript
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var Float32Array = require( '@stdlib/array/float32' );
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var addf = require( '@stdlib/math/base/ops/addf' );
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var x = new Float32Array( [ -1.0, -2.0, -3.0, -4.0, -5.0 ] );
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var y = new Float32Array( [ 1.0, 1.0, 2.0, 2.0, 3.0 ] );
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var z = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );
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smap2.ndarray( x.length, x, 1, 0, y, 1, 0, z, 1, 0, addf );
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// y => <Float32Array>[ 0.0, -1.0, -1.0, -2.0, -2.0 ]
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```
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The function accepts the following addfitional arguments:
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- **offsetX**: starting index for `x`.
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- **offsetY**: starting index for `y`.
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- **offsetZ**: starting index for `z`.
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While [`typed array`][@stdlib/array/float32] 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,
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```javascript
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var Float32Array = require( '@stdlib/array/float32' );
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var addf = require( '@stdlib/math/base/ops/addf' );
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var x = new Float32Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
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var y = new Float32Array( [ 1.0, 1.0, 2.0, 2.0, 3.0, 3.0 ] );
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var z = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
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smap2.ndarray( 3, x, 2, 1, y, -1, y.length-1, z, 1, 3, addf );
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// z => <Float32Array>[ 0.0, 0.0, 0.0, 1.0, -1.0, -1.0 ]
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
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var filledarrayBy = require( '@stdlib/array/filled-by' );
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var Float32Array = require( '@stdlib/array/float32' );
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var addf = require( '@stdlib/math/base/ops/addf' );
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var smap2 = require( '@stdlib/strided/base/smap2' );
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var x = filledarrayBy( 10, 'float32', discreteUniform( -100, 100 ) );
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console.log( x );
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var y = filledarrayBy( x.length, 'float32', discreteUniform( -100, 100 ) );
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console.log( y );
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var z = new Float32Array( x.length );
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console.log( z );
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smap2.ndarray( x.length, x, 1, 0, y, -1, y.length-1, z, 1, 0, addf );
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console.log( z );
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```
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</section>
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<!-- /.examples -->
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<!-- C interface documentation. -->
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* * *
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<section class="c">
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## C APIs
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- C usage documentation. -->
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<section class="usage">
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### Usage
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```c
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#include "stdlib/strided/base/smap2.h"
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```
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#### stdlib_strided_smap2( N, \*X, strideX, \*Y, strideY, \*Z, strideZ, fcn )
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Applies a binary function accepting and returning single-precision floating-point numbers to corresponding elements in two single-precision floating-point strided input arrays and assigns each result to an element in a single-precision floating-point strided output array.
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```c
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#include <stdint.h>
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static float addf( const float x, const float y ) {
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return x + y;
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}
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float X[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
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float Y[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
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float Z[] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
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int64_t N = 6;
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stdlib_strided_smap2( N, X, 1, Y, 1, Z, 1, addf );
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```
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The function accepts the following arguments:
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- **N**: `[in] int64_t` number of indexed elements.
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- **X**: `[in] float*` input array.
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- **strideX** `[in] int64_t` index increment for `X`.
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- **Y**: `[in] float*` input array.
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- **strideY**: `[in] int64_t` index increment for `Y`.
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- **Z**: `[out] float*` output array.
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- **strideZ**: `[in] int64_t` index increment for `Z`.
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- **fcn**: `[in] float (*fcn)( float, float )` unary function to apply.
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```c
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void stdlib_strided_smap2( const int64_t N, const float *X, const int64_t strideX, const float *Y, const int64_t strideY, float *Z, const int64_t strideZ, float (*fcn)( float, float ) );
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```
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</section>
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<!-- /.usage -->
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<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- C API usage examples. -->
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<section class="examples">
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### Examples
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```c
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#include "stdlib/strided/base/smap2.h"
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#include <stdint.h>
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#include <stdio.h>
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#include <inttypes.h>
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// Define a callback:
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static float addf( const float x, const float y ) {
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return x + y;
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}
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int main() {
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// Create input strided arrays:
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float X[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
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float Y[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
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// Create an output strided array:
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float Z[] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
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// Specify the number of elements:
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int64_t N = 6;
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// Define the strides:
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int64_t strideX = 1;
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int64_t strideY = -1;
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int64_t strideZ = 1;
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// Apply the callback:
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stdlib_strided_smap2( N, X, strideX, Y, strideY, Z, strideZ, addf );
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// Print the results:
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for ( int64_t i = 0; i < N; i++ ) {
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printf( "Z[ %"PRId64" ] = %f\n", i, Z[ i ] );
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}
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}
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```
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</section>
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<!-- /.examples -->
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</section>
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<!-- /.c -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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[@stdlib/array/float32]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/float32
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</section>
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<!-- /.links -->

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