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[v3] Improve uniform_int<>::_M_call(..., true_type)
- From: Paolo Carlini <pcarlini at suse dot de>
- To: Gcc Patch List <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 30 Oct 2007 14:07:12 +0100
- Subject: [v3] Improve uniform_int<>::_M_call(..., true_type)
Hi,
tested x86_64-linux, committed to mainline.
Paolo.
////////////////
2007-10-30 Paolo Carlini <pcarlini@suse.de>
* include/tr1_impl/random (uniform_int<>::
_M_call(_UniformRandomNumberGenerator&, result_type, result_type,
true_type)): Only declare.
* include/tr1_impl/random.tcc (uniform_int<>::
_M_call(_UniformRandomNumberGenerator&, result_type, result_type,
true_type)): Re-do, unbiased for the currently supported ranges;
add comment.
Index: include/tr1_impl/random
===================================================================
--- include/tr1_impl/random (revision 129768)
+++ include/tr1_impl/random (working copy)
@@ -1603,17 +1603,7 @@
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
Index: include/tr1_impl/random.tcc
===================================================================
--- include/tr1_impl/random.tcc (revision 129768)
+++ include/tr1_impl/random.tcc (working copy)
@@ -750,6 +750,40 @@
}
+ 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,