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| author | Paolo Carlini <paolo@gcc.gnu.org> | 2007-10-30 13:05:26 +0000 |
|---|---|---|
| committer | Paolo Carlini <paolo@gcc.gnu.org> | 2007-10-30 13:05:26 +0000 |
| commit | ebb82e27513e78bac987eda8a6cca289be3ff43d (patch) | |
| tree | 2ba79277f8e16d30c740eb3681da9226b66ffaa5 /libstdc++-v3/include | |
| parent | 19d8eb46e30f295f89708eafec1170e712565823 (diff) | |
| download | gcc-ebb82e27513e78bac987eda8a6cca289be3ff43d.zip gcc-ebb82e27513e78bac987eda8a6cca289be3ff43d.tar.gz gcc-ebb82e27513e78bac987eda8a6cca289be3ff43d.tar.bz2 | |
re PR libstdc++/33815 (tr1::uniform_int isn't uniform)
2007-10-19 Paolo Carlini <pcarlini@suse.de>
PR libstdc++/33815
* include/tr1_impl/random
(uniform_int<>::_M_call(_UniformRandomNumberGenerator&, result_type,
result_type, true_type)): Avoid the modulo (which uses the low-order
bits).
From-SVN: r129769
Diffstat (limited to 'libstdc++-v3/include')
| -rw-r--r-- | libstdc++-v3/include/tr1_impl/random | 12 | ||||
| -rw-r--r-- | libstdc++-v3/include/tr1_impl/random.tcc | 34 |
2 files changed, 35 insertions, 11 deletions
diff --git a/libstdc++-v3/include/tr1_impl/random b/libstdc++-v3/include/tr1_impl/random index 7b9b951..4ce7d8b 100644 --- a/libstdc++-v3/include/tr1_impl/random +++ b/libstdc++-v3/include/tr1_impl/random @@ -1603,17 +1603,7 @@ _GLIBCXX_BEGIN_NAMESPACE_TR1 template<typename _UniformRandomNumberGenerator> result_type _M_call(_UniformRandomNumberGenerator& __urng, - result_type __min, result_type __max, true_type) - { - // XXX Must be fixed to also work when __urng.max() - __urng.min() - // is smaller than __max - __min. - typedef typename __gnu_cxx::__add_unsigned<typename - _UniformRandomNumberGenerator::result_type>::__type __utype; - return result_type((__max - __min + 1.0L) - * (__utype(__urng()) - __utype(__urng.min())) - / (__utype(__urng.max()) - - __utype(__urng.min()) + 1.0L)) + __min; - } + result_type __min, result_type __max, true_type); template<typename _UniformRandomNumberGenerator> result_type diff --git a/libstdc++-v3/include/tr1_impl/random.tcc b/libstdc++-v3/include/tr1_impl/random.tcc index e57d609..2b0f695 100644 --- a/libstdc++-v3/include/tr1_impl/random.tcc +++ b/libstdc++-v3/include/tr1_impl/random.tcc @@ -750,6 +750,40 @@ _GLIBCXX_BEGIN_NAMESPACE_TR1 } + template<typename _IntType> + template<typename _UniformRandomNumberGenerator> + typename uniform_int<_IntType>::result_type + uniform_int<_IntType>:: + _M_call(_UniformRandomNumberGenerator& __urng, + result_type __min, result_type __max, true_type) + { + // XXX Must be fixed to work well for *arbitrary* __urng.max(), + // __urng.min(), __max, __min. Currently works fine only in the + // most common case __urng.max() - __urng.min() >= __max - __min, + // with __urng.max() > __urng.min() >= 0. + typedef typename __gnu_cxx::__add_unsigned<typename + _UniformRandomNumberGenerator::result_type>::__type __urntype; + typedef typename __gnu_cxx::__add_unsigned<result_type>::__type + __utype; + typedef typename __gnu_cxx::__conditional_type<(sizeof(__urntype) + > sizeof(__utype)), + __urntype, __utype>::__type __uctype; + + result_type __ret; + + const __urntype __urnmin = __urng.min(); + const __urntype __urnmax = __urng.max(); + const __urntype __urnrange = __urnmax - __urnmin; + const __uctype __urange = __max - __min; + const __uctype __udenom = (__urnrange <= __urange + ? 1 : __urnrange / (__urange + 1)); + do + __ret = (__urntype(__urng()) - __urnmin) / __udenom; + while (__ret > __max - __min); + + return __ret + __min; + } + template<typename _IntType, typename _CharT, typename _Traits> std::basic_ostream<_CharT, _Traits>& operator<<(std::basic_ostream<_CharT, _Traits>& __os, |