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+ runtime check of rounding mode support #8

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+ runtime check of rounding mode support #8

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29 changes: 29 additions & 0 deletions include/boost/numeric/interval/hw_rounding.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@
#ifndef BOOST_NUMERIC_INTERVAL_HW_ROUNDING_HPP
#define BOOST_NUMERIC_INTERVAL_HW_ROUNDING_HPP

#include <cassert>

#include <boost/numeric/interval/rounding.hpp>
#include <boost/numeric/interval/rounded_arith.hpp>

Expand Down Expand Up @@ -46,23 +48,50 @@ namespace boost {
namespace numeric {
namespace interval_lib {

namespace detail
{
template<class T>
struct runtime_checker
{
protected:
runtime_checker()
{
static helper _;
}

private:
struct helper
{
helper()
{
T a = -(T(-1.1) * T(10.1));
T b = +(T(+1.1) * T(10.1));
assert(a != b);
}
};
};
}

/*
* Three specializations of rounded_math<T>
*/

template<>
struct rounded_math<float>
: save_state<rounded_arith_opp<float> >
, private detail::runtime_checker<float>
{};

template<>
struct rounded_math<double>
: save_state<rounded_arith_opp<double> >
, private detail::runtime_checker<double>
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Won't this increase the runtime performance significantly if these are used in hot code paths?

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It shouldn't because it is invoking only once (static helper _, line 59). There is still some performance penalty due to the check that singleton of the type helper is initialized, but I believe that it's insignificant in comparison to the cost of switch of rounding mode.

{};

template<>
struct rounded_math<long double>
: save_state<rounded_arith_opp<long double> >
, private detail::runtime_checker<long double>
{};

} // namespace interval_lib
Expand Down