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