diff options
Diffstat (limited to 'boost/multiprecision/detail/functions/trig.hpp')
| -rw-r--r-- | boost/multiprecision/detail/functions/trig.hpp | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/boost/multiprecision/detail/functions/trig.hpp b/boost/multiprecision/detail/functions/trig.hpp index 319b708b0c..c001f955c9 100644 --- a/boost/multiprecision/detail/functions/trig.hpp +++ b/boost/multiprecision/detail/functions/trig.hpp @@ -128,7 +128,13 @@ void eval_sin(T& result, const T& x) eval_fmod(t, n_pi, t); const bool b_n_pi_is_even = eval_get_sign(t) == 0; eval_multiply(n_pi, get_constant_pi<T>()); - eval_subtract(xx, n_pi); + if (n_pi.compare(get_constant_one_over_epsilon<T>()) > 0) + { + result = ui_type(0); + return; + } + else + eval_subtract(xx, n_pi); BOOST_MATH_INSTRUMENT_CODE(xx.str(0, std::ios_base::scientific)); BOOST_MATH_INSTRUMENT_CODE(n_pi.str(0, std::ios_base::scientific)); @@ -276,7 +282,20 @@ void eval_cos(T& result, const T& x) BOOST_MATH_INSTRUMENT_CODE(n_pi.str(0, std::ios_base::scientific)); eval_multiply(t, n_pi, get_constant_pi<T>()); BOOST_MATH_INSTRUMENT_CODE(t.str(0, std::ios_base::scientific)); - eval_subtract(xx, t); + // + // If t is so large that all digits cancel the result of this subtraction + // is completely meaningless, just assume the result is zero for now... + // + // TODO We should of course do much better, see: + // "ARGUMENT REDUCTION FOR HUGE ARGUMENTS" K C Ng 1992 + // + if (n_pi.compare(get_constant_one_over_epsilon<T>()) > 0) + { + result = ui_type(1); + return; + } + else + eval_subtract(xx, t); BOOST_MATH_INSTRUMENT_CODE(xx.str(0, std::ios_base::scientific)); // Adjust signs if the multiple of pi is not even. |