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Tidy up comments.

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jzmaddock
2015-04-30 18:32:48 +01:00
parent 5c022355ac
commit a0fb417bc0
3 changed files with 120 additions and 105 deletions
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27
example/root_finding_n_example.cpp
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@@ -47,21 +47,21 @@ struct nth_functor_2deriv
BOOST_STATIC_ASSERT_MSG((N > 0) == true, "root N must be > 0!");
nth_functor_2deriv(T const& to_find_root_of) : a(to_find_root_of)
{ // Constructor stores value a to find root of, for example:
}
{ /* Constructor stores value a to find root of, for example: */ }
// using boost::math::tuple; // to return three values.
std::tuple<T, T, T> operator()(T const& x)
{ // Return f(x), f'(x) and f''(x).
{
// Return f(x), f'(x) and f''(x).
using boost::math::pow;
T fx = pow<N>(x) - a; // Difference (estimate x^n - a).
T dx = N * pow<N - 1>(x); // 1st derivative f'(x).
T d2x = N * (N - 1) * pow<N - 2 >(x); // 2nd derivative f''(x).
T fx = pow<N>(x) - a; // Difference (estimate x^n - a).
T dx = N * pow<N - 1>(x); // 1st derivative f'(x).
T d2x = N * (N - 1) * pow<N - 2 >(x); // 2nd derivative f''(x).
return std::make_tuple(fx, dx, d2x); // 'return' fx, dx and d2x.
return std::make_tuple(fx, dx, d2x); // 'return' fx, dx and d2x.
}
private:
T a; // to be 'nth_rooted'.
T a; // to be 'nth_rooted'.
};
//] [/root_finding_nth_functor_2deriv]
@@ -98,12 +98,13 @@ T nth_2deriv(T x)
typedef double guess_type; // double may restrict (exponent) range for a multiprecision T?
int exponent;
frexp(static_cast<guess_type>(x), &exponent); // Get exponent of z (ignore mantissa).
T guess = ldexp(static_cast<guess_type>(1.), exponent / N); // Rough guess is to divide the exponent by n.
frexp(static_cast<guess_type>(x), &exponent); // Get exponent of z (ignore mantissa).
T guess = ldexp(static_cast<guess_type>(1.), exponent / N); // Rough guess is to divide the exponent by n.
T min = ldexp(static_cast<guess_type>(1.) / 2, exponent / N); // Minimum possible value is half our guess.
T max = ldexp(static_cast<guess_type>(2.), exponent / N); // Maximum possible value is twice our guess.
T max = ldexp(static_cast<guess_type>(2.), exponent / N); // Maximum possible value is twice our guess.
int digits = 2 * std::numeric_limits<T>::digits / 3; // Two thirds maximum possible binary digits accuracy for type T.
int digits = std::numeric_limits<T>::digits * 0.4; // Accuracy tripples with each step, so stop when
// slightly more than one third of the digits are correct.
const boost::uintmax_t maxit = 20;
boost::uintmax_t it = maxit;
T result = halley_iterate(nth_functor_2deriv<N, T>(x), guess, min, max, digits, it);
@@ -209,4 +210,4 @@ RUN SUCCESSFUL (total time: 63ms)
/*
Throw out of range using GCC release mode :-(
*/
*/