feat: add native addon to cinv API

lib/node_modules/@stdlib/math/base/special/cinv/README.md

@@ -18,9 +18,9 @@ limitations under the License.
 
 -->
 
-# inv
+# cinv
 
-> Compute the inverse of a complex number.
+> Compute the inverse of a double-precision complex floating-point number.
 
 <section class="intro">
 
@@ -47,27 +47,23 @@ The inverse (or reciprocal) of a non-zero complex number `z = a + bi` is defined
 var cinv = require( '@stdlib/math/base/special/cinv' );
 ```
 
-#### cinv( \[out,] re1, im1 )
+#### cinv( z )
 
-Computes the inverse of a `complex` number comprised of a **real** component `re` and an **imaginary** component `im`.
+Computes the inverse of a double-precision complex floating-point number.
 
 ```javascript
-var v = cinv( 2.0, 4.0 );
-// returns [ 0.1, -0.2 ]
-```
-
-By default, the function returns real and imaginary components as a two-element `array`. To avoid unnecessary memory allocation, the function supports providing an output (destination) object.
-
-```javascript
-var Float64Array = require( '@stdlib/array/float64' );
+var Complex128 = require( '@stdlib/complex/float64' );
+var real = require( '@stdlib/complex/real' );
+var imag = require( '@stdlib/complex/imag' );
 
-var out = new Float64Array( 2 );
+var v = cinv( new Complex128( 2.0, 4.0 ) );
+// returns <Complex128>
 
-var v = cinv( out, 2.0, 4.0 );
-// returns <Float64Array>[ 0.1, -0.2 ]
+var re = real( v );
+// returns 0.1
 
-var bool = ( v === out );
-// returns true
+var im = imag( v );
+// returns -0.2
 ```
 
 </section>
@@ -82,26 +78,16 @@ var bool = ( v === out );
 
 ```javascript
 var Complex128 = require( '@stdlib/complex/float64' );
-var randu = require( '@stdlib/random/base/randu' );
-var round = require( '@stdlib/math/base/special/round' );
-var real = require( '@stdlib/complex/real' );
-var imag = require( '@stdlib/complex/imag' );
+var uniform = require( '@stdlib/random/base/uniform' );
 var cinv = require( '@stdlib/math/base/special/cinv' );
 
-var re;
-var im;
 var z1;
 var z2;
-var o;
 var i;
 
 for ( i = 0; i < 100; i++ ) {
-    re = round( randu()*100.0 ) - 50.0;
-    im = round( randu()*100.0 ) - 50.0;
-    z1 = new Complex128( re, im );
-
-    o = cinv( real(z1), imag(z1) );
-    z2 = new Complex128( o[ 0 ], o[ 1 ] );
+    z1 = new Complex128( uniform( -50.0, 50.0 ), uniform( -50.0, 50.0 ) );
+    z2 = cinv( z1 );
 
     console.log( '1.0 / (%s) = %s', z1.toString(), z2.toString() );
 }
@@ -111,6 +97,117 @@ for ( i = 0; i < 100; i++ ) {
 
 <!-- /.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/math/base/special/cinv.h"
+```
+
+#### stdlib_base_cinv( z )
+
+Computes the inverse of a double-precision complex floating-point number.
+
+```c
+#include "stdlib/complex/float64.h"
+#include "stdlib/complex/real.h"
+#include "stdlib/complex/imag.h"
+
+stdlib_complex128_t z = stdlib_complex128( 2.0, 4.0 );
+
+stdlib_complex128_t out = stdlib_base_cinv( z );
+
+double re = stdlib_real( out );
+// returns 0.1
+
+double im = stdlib_imag( out );
+// returns -0.2
+```
+
+The function accepts the following arguments:
+
+-   **z**: `[in] stdlib_complex128_t` input value.
+
+```c
+stdlib_complex128_t stdlib_base_cinv( const stdlib_complex128_t z );
+```
+
+</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/math/base/special/cinv.h"
+#include "stdlib/complex/float64.h"
+#include "stdlib/complex/reim.h"
+#include <stdio.h>
+
+int main() {
+    const stdlib_complex128_t x[] = {
+        stdlib_complex128( 3.14, 1.5 ),
+        stdlib_complex128( -3.14, -1.5 ),
+        stdlib_complex128( 0.0, 0.0 ),
+        stdlib_complex128( 0.0/0.0, 0.0/0.0 )
+    };
+
+    stdlib_complex128_t v;
+    stdlib_complex128_t y;
+    double re1;
+    double im1;
+    double re2;
+    double im2;
+    int i;
+    for ( i = 0; i < 4; i++ ) {
+        v = x[ i ];
+        y = stdlib_base_cinv( v );
+        stdlib_reim( v, &re1, &im1 );
+        stdlib_reim( y, &re2, &im2 );
+        printf( "cinv(%lf + %lfi) = %lf + %lfi\n", re1, im1, re2, im2 );
+    }
+}
+```
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
 * * *
 
 <section class="references">

lib/node_modules/@stdlib/math/base/special/cinv/benchmark/benchmark.js

@@ -21,58 +21,37 @@
 // MODULES //
 
 var bench = require( '@stdlib/bench' );
-var randu = require( '@stdlib/random/base/randu' );
-var isArray = require( '@stdlib/assert/is-array' );
+var uniform = require( '@stdlib/random/base/uniform' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var Complex128 = require( '@stdlib/complex/float64' );
+var real = require( '@stdlib/complex/real' );
+var imag = require( '@stdlib/complex/imag' );
 var pkg = require( './../package.json' ).name;
 var cinv = require( './../lib' );
 
 
 // MAIN //
 
 bench( pkg, function benchmark( b ) {
-	var re;
-	var im;
+	var values;
 	var y;
 	var i;
 
-	b.tic();
-	for ( i = 0; i < b.iterations; i++ ) {
-		re = ( randu()*1000.0 ) - 500.0;
-		im = ( randu()*1000.0 ) - 500.0;
-		y = cinv( re, im );
-		if ( y.length === 0 ) {
-			b.fail( 'should not be empty' );
-		}
-	}
-	b.toc();
-	if ( !isArray( y ) ) {
-		b.fail( 'should return an array' );
-	}
-	b.pass( 'benchmark finished' );
-	b.end();
-});
-
-bench( pkg+'::memory_reuse', function benchmark( b ) {
-	var out;
-	var re;
-	var im;
-	var y;
-	var i;
-
-	out = new Array( 2 );
+	values = [
+		new Complex128( uniform( -500.0, 500.0 ), uniform( -500.0, 500.0 ) ),
+		new Complex128( uniform( -500.0, 500.0 ), uniform( -500.0, 500.0 ) )
+	];
 
 	b.tic();
 	for ( i = 0; i < b.iterations; i++ ) {
-		re = ( randu()*1000.0 ) - 500.0;
-		im = ( randu()*1000.0 ) - 500.0;
-		y = cinv( out, re, im );
-		if ( y.length === 0 ) {
-			b.fail( 'should not be empty' );
+		y = cinv( values[ i%values.length ] );
+		if ( isnan( real( y ) ) ) {
+			b.fail( 'should not return NaN' );
 		}
 	}
 	b.toc();
-	if ( !isArray( y ) ) {
-		b.fail( 'should return an array' );
+	if ( isnan( imag( y ) ) ) {
+		b.fail( 'should not return not NaN' );
 	}
 	b.pass( 'benchmark finished' );
 	b.end();