Adding upstream version 14.2.21.upstream/14.2.21upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/src/boost/libs/math/example/autodiff_fourth_power.cpp b/src/boost/libs/math/example/autodiff_fourth_power.cpp
new file mode 100644
index 00000000..50f280b6
--- /dev/null
+++ b/src/boost/libs/math/example/autodiff_fourth_power.cpp
@@ -0,0 +1,34 @@
+//           Copyright Matthew Pulver 2018 - 2019.
+// Distributed under the Boost Software License, Version 1.0.
+//      (See accompanying file LICENSE_1_0.txt or copy at
+//           https://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/math/differentiation/autodiff.hpp>
+#include <iostream>
+
+template <typename T>
+T fourth_power(T const& x) {
+  T x4 = x * x;  // retval in operator*() uses x4's memory via NRVO.
+  x4 *= x4;      // No copies of x4 are made within operator*=() even when squaring.
+  return x4;     // x4 uses y's memory in main() via NRVO.
+}
+
+int main() {
+  using namespace boost::math::differentiation;
+
+  constexpr unsigned Order = 5;                  // Highest order derivative to be calculated.
+  auto const x = make_fvar<double, Order>(2.0);  // Find derivatives at x=2.
+  auto const y = fourth_power(x);
+  for (unsigned i = 0; i <= Order; ++i)
+    std::cout << "y.derivative(" << i << ") = " << y.derivative(i) << std::endl;
+  return 0;
+}
+/*
+Output:
+y.derivative(0) = 16
+y.derivative(1) = 32
+y.derivative(2) = 48
+y.derivative(3) = 48
+y.derivative(4) = 24
+y.derivative(5) = 0
+**/