feat: add C implementation for blas/ext/base/ndarray/dwhere

lib/node_modules/@stdlib/blas/ext/base/ndarray/dwhere/README.md

@@ -111,6 +111,138 @@ console.log( ndarray2array( out ) );
 
 <!-- /.examples -->
 
+<!-- C interface documentation. -->
+
+* * *
+
+<section class="c">
+
+## C APIs
+
+<section class="usage">
+
+### Usage
+
+```c
+#include "stdlib/blas/ext/base/ndarray/dwhere.h"
+```
+
+#### stdlib_blas_ext_dwhere( arrays )
+
+Takes elements from one of two one-dimensional double-precision floating-point ndarrays depending on a condition.
+
+The function accepts the following arguments:
+
+-   **arrays**: `[in] struct ndarray**` list containing the following ndarrays:
+
+    -   `[in] struct ndarray*` a one-dimensional boolean condition ndarray.
+    -   `[in] struct ndarray*` first one-dimensional double-precision input ndarray.
+    -   `[in] struct ndarray*` second one-dimensional double-precision input ndarray.
+    -   `[out] struct ndarray*` a one-dimensional double-precision output ndarray.
+
+```c
+void stdlib_blas_ext_dwhere( const struct ndarray *arrays[] );
+```
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+### Notes
+
+-   The output ndarray is modified in-place.
+-   A nonzero condition byte selects an element from the first input ndarray; a zero byte selects an element from the second input ndarray.
+-   Strides and offsets in C ndarray metadata are specified in units of bytes.
+
+</section>
+
+<!-- /.notes -->
+
+<section class="examples">
+
+### Examples
+
+```c
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+#include "stdlib/blas/ext/base/ndarray/dwhere.h"
+#include "stdlib/ndarray/ctor.h"
+#include "stdlib/ndarray/dtypes.h"
+#include "stdlib/ndarray/index_modes.h"
+#include "stdlib/ndarray/orders.h"
+#include "stdlib/ndarray/base/bytes_per_element.h"
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+int main( void ) {
+    // Create data buffers:
+    uint8_t dataC[] = { 1, 0, 1, 0, 1 };
+    double dataX[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
+    double dataY[] = { 6.0, 7.0, 8.0, 9.0, 10.0 };
+    double dataOut[] = { 0.0, 0.0, 0.0, 0.0, 0.0 };
+    int64_t shape[] = { 5 };
+    int64_t strideC[] = { STDLIB_NDARRAY_BOOL_BYTES_PER_ELEMENT };
+    int64_t stride[] = { STDLIB_NDARRAY_FLOAT64_BYTES_PER_ELEMENT };
+    int8_t submodes[] = { STDLIB_NDARRAY_INDEX_ERROR };
+
+    // Create ndarrays:
+    struct ndarray *condition = stdlib_ndarray_allocate( STDLIB_NDARRAY_BOOL, dataC, 1, shape, strideC, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );
+
+    // cppcheck-suppress invalidPointerCast
+    struct ndarray *x = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT64, (uint8_t *)dataX, 1, shape, stride, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );
+
+    // cppcheck-suppress invalidPointerCast
+    struct ndarray *y = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT64, (uint8_t *)dataY, 1, shape, stride, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );
+
+    // cppcheck-suppress invalidPointerCast
+    struct ndarray *out = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT64, (uint8_t *)dataOut, 1, shape, stride, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );
+    if ( condition == NULL || x == NULL || y == NULL || out == NULL ) {
+        fprintf( stderr, "Error allocating memory.\n" );
+        stdlib_ndarray_free( condition );
+        stdlib_ndarray_free( x );
+        stdlib_ndarray_free( y );
+        stdlib_ndarray_free( out );
+        exit( 1 );
+    }
+    const struct ndarray *arrays[] = { condition, x, y, out };
+    stdlib_blas_ext_dwhere( arrays );
+    for ( int i = 0; i < 5; i++ ) {
+        printf( "out[ %i ] = %lf\n", i, dataOut[ i ] );
+    }
+    stdlib_ndarray_free( condition );
+    stdlib_ndarray_free( x );
+    stdlib_ndarray_free( y );
+    stdlib_ndarray_free( out );
+}
+```
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
 <!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
 
 <section class="related">

lib/node_modules/@stdlib/blas/ext/base/ndarray/dwhere/benchmark/benchmark.native.js

@@ -0,0 +1,121 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var resolve = require( 'path' ).resolve;
+var bench = require( '@stdlib/bench' );
+var tryRequire = require( '@stdlib/utils/try-require' );
+var bernoulli = require( '@stdlib/random/array/bernoulli' );
+var uniform = require( '@stdlib/random/uniform' );
+var BooleanVector = require( '@stdlib/ndarray/vector/bool' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var format = require( '@stdlib/string/format' );
+var pkg = require( './../package.json' ).name;
+var dwhere = tryRequire( resolve( __dirname, './../lib/native.js' ) );
+var opts = {
+	'skip': ( dwhere instanceof Error )
+};
+
+
+// VARIABLES //
+
+var options = {
+	'dtype': 'float64'
+};
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - ndarray length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+	var condition;
+	var cbuf;
+	var out;
+	var x;
+	var y;
+
+	cbuf = bernoulli( len, 0.5, {
+		'dtype': 'uint8'
+	});
+	condition = new BooleanVector( cbuf.buffer );
+	out = uniform( [ len ], -100.0, 100.0, options );
+	x = uniform( [ len ], -100.0, 100.0, options );
+	y = uniform( [ len ], -100.0, 100.0, options );
+	return benchmark;
+
+	/**
+	* Benchmark function.
+	*
+	* @private
+	* @param {Benchmark} b - benchmark instance
+	*/
+	function benchmark( b ) {
+		var v;
+		var i;
+
+		b.tic();
+		for ( i = 0; i < b.iterations; i++ ) {
+			v = dwhere( [ condition, x, y, out ] );
+			if ( typeof v !== 'object' ) {
+				b.fail( 'should return an ndarray' );
+			}
+		}
+		b.toc();
+		if ( typeof v !== 'object' ) {
+			b.fail( 'should return an ndarray' );
+		}
+		b.pass( 'benchmark finished' );
+		b.end();
+	}
+}
+
+
+// MAIN //
+
+/**
+* Main execution sequence.
+*
+* @private
+*/
+function main() {
+	var len;
+	var min;
+	var max;
+	var f;
+	var i;
+
+	min = 1; // 10^min
+	max = 6; // 10^max
+
+	for ( i = min; i <= max; i++ ) {
+		len = pow( 10, i );
+		f = createBenchmark( len );
+		bench( format( '%s:len=%d', pkg, len ), opts, f );
+	}
+}
+
+main();