feat: add C implementation for math/base/special/gammainc

lib/node_modules/@stdlib/math/base/special/gammainc/test/test.native.js

@@ -43,7 +43,7 @@
 var largeXSmallS = require( './fixtures/cpp/large_x_small_s.json' );
 var largeXMediumS = require( './fixtures/cpp/large_x_medium_s.json' );
 
 // TODO: Add this to `test.js` once the JS implementation matches the latest Boost C++ implementation.
 var largeXLargeS = require( './fixtures/cpp/large_x_large_s.json' );
 
 
@@ -447,8 +447,8 @@
 			t.strictEqual( isSameValue( actual, PINF ), true, 'returns expected value' );
 			continue;
 		}
-		// NOTE: The difference is high because some of the expected values are very large.
-		t.strictEqual( ulpdiff( actual, expected[ i ] ) <= 534, true, 'returns expected value within 534 ulp' );
+		// NOTE: The difference is high because some of the expected values are very large and the compiler optimizations have been disabled.
+		t.strictEqual( ulpdiff( actual, expected[ i ] ) <= 947, true, 'returns expected value within 947 ulp' );
 	}
 	t.end();
 });
@@ -470,8 +470,8 @@
 			t.strictEqual( isSameValue( actual, PINF ), true, 'returns expected value' );
 			continue;
 		}
-		// NOTE: The difference is high because some of the expected values are very large.
-		t.strictEqual( ulpdiff( actual, expected[ i ] ) <= 969, true, 'returns expected value within 969 ulp' );
+		// NOTE: The difference is high because some of the expected values are very large and the compiler optimizations have been disabled.
+		t.strictEqual( ulpdiff( actual, expected[ i ] ) <= 1544, true, 'returns expected value within 1544 ulp' );
 	}
 	t.end();
 });