feat: add C implementation for stats/base/ndarray/dvariancetk

PR-URL: #14794
Reviewed-by: Athan Reines <kgryte@gmail.com>
Ref: #14034

Author: ujjwalv01

lib/node_modules/@stdlib/stats/base/ndarray/dvariancetk/README.md

@@ -168,6 +168,176 @@ console.log( v );
 
 <!-- /.examples -->
 
+<!-- C interface documentation. -->
+
+* * *
+
+<section class="c">
+
+## C APIs
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- C usage documentation. -->
+
+<section class="usage">
+
+### Usage
+
+```c
+#include "stdlib/stats/base/ndarray/dvariancetk.h"
+```
+
+#### stdlib_stats_dvariancetk( arrays )
+
+Computes the variance of a one-dimensional double-precision floating-point ndarray using a one-pass textbook algorithm.
+
+```c
+#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>
+
+// Create an ndarray:
+const double data[] = { 1.0, -2.0, 2.0 };
+int64_t shape[] = { 3 };
+int64_t strides[] = { STDLIB_NDARRAY_FLOAT64_BYTES_PER_ELEMENT };
+int8_t submodes[] = { STDLIB_NDARRAY_INDEX_ERROR };
+
+struct ndarray *x = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT64, (uint8_t *)data, 1, shape, strides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );
+
+// Create an ndarray for specifying the degrees of freedom adjustment:
+const double cdata[] = { 1.0 };
+int64_t cstrides[] = { 0 };
+struct ndarray *corr = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT64, (uint8_t *)cdata, 0, NULL, cstrides, 0, STDLIB_NDARRAY_ROW_MAJOR, STDLIB_NDARRAY_INDEX_ERROR, 1, submodes );
+
+// Compute the result:
+const struct ndarray *arrays[] = { x, corr };
+double v = stdlib_stats_dvariancetk( arrays );
+// returns ~4.3333
+
+// Free allocated memory:
+stdlib_ndarray_free( x );
+stdlib_ndarray_free( corr );
+```
+
+The function accepts the following arguments:
+
+-   **arrays**: `[in] struct ndarray**` list containing the following ndarrays:
+
+    -   `[in] struct ndarray*` a one-dimensional input ndarray.
+    -   `[in] struct ndarray*` a zero-dimensional ndarray specifying the degrees of freedom adjustment. Providing a non-zero degrees of freedom adjustment has the effect of adjusting the divisor during the calculation of the [variance][variance] according to `N-c` where `N` is the number of elements in the input ndarray and `c` corresponds to the provided degrees of freedom adjustment. When computing the [variance][variance] of a population, setting this parameter to `0` is the standard choice (i.e., the provided array contains data constituting an entire population). When computing the corrected sample [variance][variance], setting this parameter to `1` is the standard choice (i.e., the provided array contains data sampled from a larger population; this is commonly referred to as Bessel's correction). 
+
+```c
+double stdlib_stats_dvariancetk( const struct ndarray *arrays[] );
+```
+
+</section>
+
+<!-- /.usage -->
+
+<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+</section>
+
+<!-- /.notes -->
+
+<!-- C API usage examples. -->
+
+<section class="examples">
+
+### Examples
+
+```c
+#include "stdlib/stats/base/ndarray/dvariancetk.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 a data buffer:
+    const double data[] = { 1.0, -2.0, 3.0, -4.0, 5.0, -6.0, 7.0, -8.0 };
+
+    // Specify the number of array dimensions:
+    const int64_t ndims = 1;
+
+    // Specify the array shape:
+    int64_t shape[] = { 4 };
+
+    // Specify the array strides:
+    int64_t strides[] = { 2*STDLIB_NDARRAY_FLOAT64_BYTES_PER_ELEMENT };
+
+    // Specify the byte offset:
+    const int64_t offset = 0;
+
+    // Specify the array order:
+    const enum STDLIB_NDARRAY_ORDER order = STDLIB_NDARRAY_ROW_MAJOR;
+
+    // Specify the index mode:
+    const enum STDLIB_NDARRAY_INDEX_MODE imode = STDLIB_NDARRAY_INDEX_ERROR;
+
+    // Specify the subscript index modes:
+    int8_t submodes[] = { STDLIB_NDARRAY_INDEX_ERROR };
+    const int64_t nsubmodes = 1;
+
+    // Create an ndarray:
+    struct ndarray *x = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT64, (uint8_t *)data, ndims, shape, strides, offset, order, imode, nsubmodes, submodes );
+    if ( x == NULL ) {
+        fprintf( stderr, "Error allocating memory.\n" );
+        exit( 1 );
+    }
+
+    // Create a data buffer for an ndarray specifying the degrees of freedom adjustment:
+    const double cdata[] = { 1.0 };
+
+    // Specify the array strides:
+    int64_t cstrides[] = { 0 };
+
+    // Create an ndarray for the degrees of freedom adjustment:
+    struct ndarray *corr = stdlib_ndarray_allocate( STDLIB_NDARRAY_FLOAT64, (uint8_t *)cdata, 0, NULL, cstrides, 0, order, imode, nsubmodes, submodes );
+    if ( corr == NULL ) {
+        fprintf( stderr, "Error allocating memory.\n" );
+        exit( 1 );
+    }
+
+    // Define a list of ndarrays:
+    const struct ndarray *arrays[] = { x, corr };
+
+    // Compute the result:
+    double v = stdlib_stats_dvariancetk( arrays );
+
+    // Print the result:
+    printf( "result: %lf\n", v );
+
+    // Free allocated memory:
+    stdlib_ndarray_free( x );
+    stdlib_ndarray_free( corr );
+}
+```
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
 * * *
 
 <section class="references">

lib/node_modules/@stdlib/stats/base/ndarray/dvariancetk/benchmark/benchmark.js

@@ -27,7 +27,7 @@ var pow = require( '@stdlib/math/base/special/pow' );
 var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
 var format = require( '@stdlib/string/format' );
 var pkg = require( './../package.json' ).name;
-var dvariancetk = require( './../lib' );
+var dvariancetk = require( './../lib/main.js' );
 
 
 // VARIABLES //

lib/node_modules/@stdlib/stats/base/ndarray/dvariancetk/benchmark/benchmark.native.js

@@ -0,0 +1,110 @@
+/**
+* @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 uniform = require( '@stdlib/random/uniform' );
+var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var format = require( '@stdlib/string/format' );
+var tryRequire = require( '@stdlib/utils/try-require' );
+var pkg = require( './../package.json' ).name;
+
+
+// VARIABLES //
+
+var dvariancetk = tryRequire( resolve( __dirname, './../lib/native.js' ) );
+var opts = {
+	'skip': ( dvariancetk instanceof Error )
+};
+var options = {
+	'dtype': 'float64'
+};
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - array length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+	var correction = scalar2ndarray( 1.0, options );
+	var x = uniform( [ len ], -10.0, 10.0, 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 = dvariancetk( [ x, correction ] );
+			if ( isnan( v ) ) {
+				b.fail( 'should not return NaN' );
+			}
+		}
+		b.toc();
+		if ( isnan( v ) ) {
+			b.fail( 'should not return NaN' );
+		}
+		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::native:len=%d', pkg, len ), opts, f );
+	}
+}
+
+main();