fix: chi pdf c implementation and tests

---
type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:
  - task: lint_filenames
    status: passed
  - task: lint_editorconfig
    status: passed
  - task: lint_markdown
    status: na
  - task: lint_package_json
    status: na
  - task: lint_repl_help
    status: na
  - task: lint_javascript_src
    status: na
  - task: lint_javascript_cli
    status: na
  - task: lint_javascript_examples
    status: na
  - task: lint_javascript_tests
    status: passed
  - task: lint_javascript_benchmarks
    status: passed
  - task: lint_python
    status: na
  - task: lint_r
    status: na
  - task: lint_c_src
    status: na
  - task: lint_c_examples
    status: na
  - task: lint_c_benchmarks
    status: na
  - task: lint_c_tests_fixtures
    status: na
  - task: lint_shell
    status: na
  - task: lint_typescript_declarations
    status: na
  - task: lint_typescript_tests
    status: na
  - task: lint_license_headers
    status: passed
---

Author: Planeshifter

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

@@ -22,8 +22,7 @@
 
 var bench = require( '@stdlib/bench' );
 var Float64Array = require( '@stdlib/array/float64' );
-var uniform = require( '@stdlib/random/array/uniform' );
-var randu = require( '@stdlib/random/base/randu' );
+var uniform = require( '@stdlib/random/base/uniform' );
 var isnan = require( '@stdlib/math/base/assert/is-nan' );
 var pkg = require( './../package.json' ).name;
 var pdf = require( './../lib' );
@@ -42,8 +41,8 @@ bench( pkg, function benchmark( b ) {
 	x = new Float64Array( len );
 	k = new Float64Array( len );
 	for ( i = 0; i < len; i++ ) {
-		x[ i ] = ( randu() * 20.0 ) - 10.0;
-		k[ i ] = ( randu() * 20.0 ) + 0.1;
+		x[ i ] = uniform( -10.0, 10.0 );
+		k[ i ] = uniform( 0.1, 20.1 );
 	}
 
 	b.tic();
@@ -61,7 +60,7 @@ bench( pkg, function benchmark( b ) {
 	b.end();
 });
 
-bench( pkg + ':factory', function benchmark( b ) {
+bench( pkg+':factory', function benchmark( b ) {
 	var mypdf;
 	var k;
 	var x;
@@ -70,7 +69,10 @@ bench( pkg + ':factory', function benchmark( b ) {
 
 	k = 2.0;
 	mypdf = pdf.factory( k );
-	x = uniform( 100, -2.0, 2.0 );
+	x = new Float64Array( 100 );
+	for ( i = 0; i < 100; i++ ) {
+		x[ i ] = uniform( -2.0, 2.0 );
+	}
 
 	b.tic();
 	for ( i = 0; i < b.iterations; i++ ) {

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

@@ -39,7 +39,7 @@ var opts = {
 
 // MAIN //
 
-bench( pkg + '::native', opts, function benchmark( b ) {
+bench( pkg+'::native', opts, function benchmark( b ) {
 	var len;
 	var k;
 	var x;

lib/node_modules/@stdlib/stats/base/dists/chi/pdf/test/test.native.js

@@ -59,14 +59,23 @@ tape( 'if provided `NaN` for any parameter, the function returns `NaN`', opts, f
 	t.end();
 });
 
-tape( 'if provided a non-positive `k`, the function returns `NaN`', opts, function test( t ) {
+tape( 'if provided a negative `k`, the function returns `NaN`', opts, function test( t ) {
 	var y;
 
 	y = pdf( 2.0, -1.0 );
 	t.equal( isnan( y ), true, 'returns NaN' );
 
+	t.end();
+});
+
+tape( 'if `k` equals `0`, the function evaluates a degenerate distribution centered at `0`', opts, function test( t ) {
+	var y;
+
+	y = pdf( 0.0, 0.0 );
+	t.equal( y, PINF, 'returns +infinity for x equal to 0' );
+
 	y = pdf( 2.0, 0.0 );
-	t.equal( isnan( y ), true, 'returns NaN' );
+	t.equal( y, 0.0, 'returns 0' );
 
 	t.end();
 });