feat: add C implementation for stats/base/dists/lognormal/pdf

lib/node_modules/@stdlib/stats/base/dists/lognormal/pdf/README.md

@@ -116,7 +116,8 @@ y = mypdf( 2.0 );
 <!-- eslint no-undef: "error" -->
 
 ```javascript
-var randu = require( '@stdlib/random/base/randu' );
+var uniform = require( '@stdlib/random/base/uniform' );
+var EPS = require( '@stdlib/constants/float64/eps' );
 var pdf = require( '@stdlib/stats/base/dists/lognormal/pdf' );
 
 var sigma;
@@ -126,9 +127,9 @@ var y;
 var i;
 
 for ( i = 0; i < 10; i++ ) {
-    x = randu() * 10.0;
-    mu = (randu() * 10.0) - 5.0;
-    sigma = randu() * 20.0;
+    x = uniform( 0.1, 10.0 );
+    mu = uniform( -5.0, 5.0 );
+    sigma = uniform( EPS, 5.0 );
     y = pdf( x, mu, sigma );
     console.log( 'x: %d, µ: %d, σ: %d, f(x;µ,σ): %d', x.toFixed( 4 ), mu.toFixed( 4 ), sigma.toFixed( 4 ), y.toFixed( 4 ) );
 }
@@ -138,6 +139,106 @@ for ( i = 0; i < 10; i++ ) {
 
 <!-- /.examples -->
 
+<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="references">
+
+<!-- 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/dists/lognormal/pdf.h"
+```
+
+#### stdlib_base_dists_lognormal_pdf( x, mu, sigma )
+
+Evaluates the [probability density function][pdf] (PDF) of a [lognormal][lognormal-distribution] distribution with parameters input value `x`, location parameter `mu` and scale parameter `sigma`.
+
+```c
+double y = stdlib_base_dists_lognormal_pdf( 2.0, 0.0, 1.0 );
+// returns ~0.157
+```
+
+The function accepts the following arguments:
+
+-   **x**: `[in] double` input value.
+-   **mu**: `[in] double` location parameter.
+-   **sigma**: `[in] double` scale parameter.
+
+```c
+double stdlib_base_dists_lognormal_pdf( const double x, const double mu, const double sigma );
+```
+
+</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/dists/lognormal/pdf.h"
+#include "stdlib/constants/float64/eps.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+static double random_uniform( const double min, const double max ) {
+    double v = (double)rand() / ( (double)RAND_MAX + 1.0 );
+    return min + ( v*(max-min) );
+}
+
+int main( void ) {
+    double sigma;
+    double mu;
+    double x;
+    double y;
+    int i;
+
+    for ( i = 0; i < 25; i++ ) {
+        x = random_uniform( 0.1, 10.0 );
+        mu = random_uniform( -5.0, 5.0 );
+        sigma = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 5.0 );
+        y = stdlib_base_dists_lognormal_pdf( x, mu, sigma );
+        printf( "x: %lf, mu: %lf, sigma: %lf, f(x;mu,sigma): %lf\n", x, mu, sigma, y );
+    }
+}
+```
+
+</section>
+
+<!-- /.references -->
+
+
 <!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
 
 <section class="related">

lib/node_modules/@stdlib/stats/base/dists/lognormal/pdf/benchmark/benchmark.js

@@ -21,7 +21,8 @@
 // MODULES //
 
 var bench = require( '@stdlib/bench' );
-var randu = require( '@stdlib/random/base/randu' );
+var uniform = require( '@stdlib/random/base/uniform' );
+var Float64Array = require( '@stdlib/array/float64' );
 var isnan = require( '@stdlib/math/base/assert/is-nan' );
 var EPS = require( '@stdlib/constants/float64/eps' );
 var pkg = require( './../package.json' ).name;
@@ -32,17 +33,25 @@ var pdf = require( './../lib' );
 
 bench( pkg, function benchmark( b ) {
 	var sigma;
+	var len;
 	var mu;
 	var x;
 	var y;
 	var i;
 
+	len = 100;
+	x = new Float64Array( len );
+	mu = new Float64Array( len );
+	sigma = new Float64Array( len );
+	for ( i = 0; i < len; i++ ) {
+		x[ i ] = uniform( 0.1, 20.0 );
+		mu[ i ] = uniform( -5.0, 5.0 );
+		sigma[ i ] = uniform( EPS, 5.0 );
+	}
+
 	b.tic();
 	for ( i = 0; i < b.iterations; i++ ) {
-		x = ( randu()*100.0 ) - 100;
-		mu = ( randu()*100.0 ) - 50.0;
-		sigma = ( randu()*20.0 ) + EPS;
-		y = pdf( x, mu, sigma );
+		y = pdf( x[ i % len ], mu[ i % len ], sigma[ i % len ] );
 		if ( isnan( y ) ) {
 			b.fail( 'should not return NaN' );
 		}
@@ -69,7 +78,7 @@ bench( pkg+':factory', function benchmark( b ) {
 
 	b.tic();
 	for ( i = 0; i < b.iterations; i++ ) {
-		x = randu() * 50.0;
+		x = uniform( 0.1, 50.0 );
 		y = mypdf( x );
 		if ( isnan( y ) ) {
 			b.fail( 'should not return NaN' );

lib/node_modules/@stdlib/stats/base/dists/lognormal/pdf/benchmark/benchmark.native.js

@@ -0,0 +1,74 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2025 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 Float64Array = require( '@stdlib/array/float64' );
+var tryRequire = require( '@stdlib/utils/try-require' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var EPS = require( '@stdlib/constants/float64/eps' );
+var uniform = require( '@stdlib/random/base/uniform' );
+var pkg = require( './../package.json' ).name;
+
+
+// VARIABLES //
+
+var pdf = tryRequire( resolve( __dirname, './../lib/native.js' ) );
+var opts = {
+	'skip': ( pdf instanceof Error )
+};
+
+
+// MAIN //
+
+bench( pkg+'::native', opts, function benchmark( b ) {
+	var sigma;
+	var len;
+	var mu;
+	var x;
+	var y;
+	var i;
+
+	len = 100;
+	x = new Float64Array( len );
+	mu = new Float64Array( len );
+	sigma = new Float64Array( len );
+	for ( i = 0; i < len; i++ ) {
+		x[ i ] = uniform( 0.1, 20.0 );
+		mu[ i ] = uniform( -5.0, 5.0 );
+		sigma[ i ] = uniform( EPS, 5.0 );
+	}
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		y = pdf( x[ i % len ], mu[ i % len ], sigma[ i % len ] );
+		if ( isnan( y ) ) {
+			b.fail( 'should not return NaN' );
+		}
+	}
+	b.toc();
+	if ( isnan( y ) ) {
+		b.fail( 'should not return NaN' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});