1 files changed, 126 insertions, 0 deletions
diff --git a/src/boost/libs/math/test/gegenbauer_test.cpp b/src/boost/libs/math/test/gegenbauer_test.cpp
new file mode 100644
index 000000000..7e1ae6b7d
--- /dev/null
+++ b/src/boost/libs/math/test/gegenbauer_test.cpp
@@ -0,0 +1,126 @@
+/*
+ * Copyright Nick Thompson, 2019
+ * Use, modification and distribution are subject to the
+ * Boost Software License, Version 1.0. (See accompanying file
+ * LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include "math_unit_test.hpp"
+#include <numeric>
+#include <utility>
+#include <random>
+#include <cmath>
+#include <boost/core/demangle.hpp>
+#include <boost/math/special_functions/gegenbauer.hpp>
+#ifdef BOOST_HAS_FLOAT128
+#include <boost/multiprecision/float128.hpp>
+using boost::multiprecision::float128;
+#endif
+
+using std::abs;
+using boost::math::gegenbauer;
+using boost::math::gegenbauer_derivative;
+
+template<class Real>
+void test_parity()
+{
+    std::mt19937 gen(323723);
+    std::uniform_real_distribution<Real> xdis(-1, +1);
+    std::uniform_real_distribution<Real> lambdadis(-0.5, 1);
+
+    for(unsigned n = 0; n < 50; ++n) {
+        unsigned calls = 50;
+        unsigned i = 0;
+        while(i++ < calls) {
+            Real x = xdis(gen);
+            Real lambda = lambdadis(gen);
+            if (n & 1) {
+                CHECK_ULP_CLOSE(gegenbauer(n, lambda, -x), -gegenbauer(n, lambda, x), 0);
+            }
+            else {
+                CHECK_ULP_CLOSE(gegenbauer(n, lambda, -x), gegenbauer(n, lambda, x), 0);
+            }
+        }
+    }
+}
+
+template<class Real>
+void test_quadratic()
+{
+    Real lambda = 1/Real(4);
+    auto c2 = [&](Real x) { return -lambda + 2*lambda*(1+lambda)*x*x; };
+
+    Real x = -1;
+    Real h = 1/Real(256);
+    while (x < 1) {
+        Real expected = c2(x);
+        Real computed = gegenbauer(2, lambda, x);
+        CHECK_ULP_CLOSE(expected, computed, 0);
+        x += h;
+    }
+}
+
+template<class Real>
+void test_cubic()
+{
+    Real lambda = 1/Real(4);
+    auto c3 = [&](Real x) { return lambda*(1+lambda)*x*(-2 + 4*(2+lambda)*x*x/3); };
+
+    Real x = -1;
+    Real h = 1/Real(256);
+    while (x < 1) {
+        Real expected = c3(x);
+        Real computed = gegenbauer(3, lambda, x);
+        CHECK_ULP_CLOSE(expected, computed, 4);
+        x += h;
+    }
+}
+
+template<class Real>
+void test_derivative()
+{
+    Real lambda = 0.5;
+    auto c3_prime = [&](Real x) { return 2*lambda*(lambda+1)*(-1 + 2*(lambda+2)*x*x); };
+    auto c3_double_prime = [&](Real x) { return 8*lambda*(lambda+1)*(lambda+2)*x; };
+    Real x = -1;
+    Real h = 1/Real(256);
+    while (x < 1) {
+        Real expected = c3_prime(x);
+        Real computed = gegenbauer_derivative(3, lambda, x, 1);
+        CHECK_ULP_CLOSE(expected, computed, 1);
+
+        expected = c3_double_prime(x);
+        computed = gegenbauer_derivative(3, lambda, x, 2);
+        CHECK_ULP_CLOSE(expected, computed, 1);
+
+        x += h;
+    }
+
+}
+
+
+
+int main()
+{
+    test_parity<float>();
+    test_parity<double>();
+    test_parity<long double>();
+
+    test_quadratic<float>();
+    test_quadratic<double>();
+    test_quadratic<long double>();
+
+    test_cubic<double>();
+    test_cubic<long double>();
+
+    test_derivative<float>();
+    test_derivative<double>();
+    test_derivative<long double>();
+
+#ifdef BOOST_HAS_FLOAT128
+    test_quadratic<boost::multiprecision::float128>();
+    test_cubic<boost::multiprecision::float128>();
+#endif
+
+    return boost::math::test::report_errors();
+}