我写了这段代码:
std::pair<std::weak_ptr<Node>, size_t> NodeSelector::rouletteWheel() const {
const std::uniform_real_distribution<long double> urd;
size_t i = 0;
for(auto rnd = urd(shared_random_engine); rnd >= 0; ++i) {
rnd -= getNormValue(i);
}
return std::make_pair(entries_[i - 1], i - 1);
}
以这种方式初始化“shared_random_engine”的位置(在单独的.h文件中)
std::minstd_rand shared_random_engine(static_cast<unsigned int>(42));
只要我在Windows上编译它,一切都很完美,但是当我尝试使用g ++ 7.3.0在Ubuntu 18.04.2上编译时,我收到此错误:
montecarlo.cpp: In member function ‘std::pair<std::weak_ptr<MonteCarloNode>, long unsigned int> NodeSelector::rouletteWheel() const’:
montecarlo.cpp:728:41: error: no match for call to ‘(const std::uniform_real_distribution<long double>) (std::minstd_rand&)’
for(auto rnd = urd(shared_random_engine); rnd >= 0; ++i) {
^
In file included from /usr/include/c++/7/random:49:0,
from selector.h:15,
from montecarlo.h:13,
from montecarlo.cpp:7:
/usr/include/c++/7/bits/random.h:1813:2: note: candidate: std::uniform_real_distribution<_RealType>::result_type std::uniform_real_distribution<_RealType>::operator()(_UniformRandomNumberGenerator&) [with _UniformRandomNumberGenerator = std::linear_congruential_engine<long unsigned int, 48271, 0, 2147483647>; _RealType = long double; std::uniform_real_distribution<_RealType>::result_type = long double] <near match>
operator()(_UniformRandomNumberGenerator& __urng)
^~~~~~~~
/usr/include/c++/7/bits/random.h:1813:2: note: passing ‘const std::uniform_real_distribution<long double>*’ as ‘this’ argument discards qualifiers
/usr/include/c++/7/bits/random.h:1818:2: note: candidate: template<class _UniformRandomNumberGenerator> std::uniform_real_distribution<_RealType>::result_type std::uniform_real_distribution<_RealType>::operator()(_UniformRandomNumberGenerator&, const std::uniform_real_distribution<_RealType>::param_type&) [with _UniformRandomNumberGenerator = _UniformRandomNumberGenerator; _RealType = long double]
operator()(_UniformRandomNumberGenerator& __urng,
^~~~~~~~
/usr/include/c++/7/bits/random.h:1818:2: note: template argument deduction/substitution failed:
montecarlo.cpp:728:41: note: candidate expects 2 arguments, 1 provided
for(auto rnd = urd(shared_random_engine); rnd >= 0; ++i) {
^
由于错误的最后几行告诉我预期有2个参数,因此我按以下方式更改了代码:
for(auto rnd = urd(shared_random_engine, urd.param())
在Windows上,它仍然可以正常工作,但在Ubuntu上我收到此错误,现在告诉我只传递一个参数:
montecarlo.cpp: In member function ‘std::pair<std::weak_ptr<MonteCarloNode>, long unsigned int> NodeSelector::rouletteWheel() const’:
montecarlo.cpp:728:54: error: no match for call to ‘(const std::uniform_real_distribution<long double>) (std::minstd_rand&, std::uniform_real_distribution<long double>::param_type)’
for(auto rnd = urd(shared_random_engine, urd.param()); rnd >= 0; ++i) {
^
In file included from /usr/include/c++/7/random:49:0,
from selector.h:15,
from montecarlo.h:13,
from montecarlo.cpp:7:
/usr/include/c++/7/bits/random.h:1813:2: note: candidate: template<class _UniformRandomNumberGenerator> std::uniform_real_distribution<_RealType>::result_type std::uniform_real_distribution<_RealType>::operator()(_UniformRandomNumberGenerator&) [with _UniformRandomNumberGenerator = _UniformRandomNumberGenerator; _RealType = long double]
operator()(_UniformRandomNumberGenerator& __urng)
^~~~~~~~
/usr/include/c++/7/bits/random.h:1813:2: note: template argument deduction/substitution failed:
montecarlo.cpp:728:54: note: candidate expects 1 argument, 2 provided
for(auto rnd = urd(shared_random_engine, urd.param()); rnd >= 0; ++i) {
^
In file included from /usr/include/c++/7/random:49:0,
from selector.h:15,
from montecarlo.h:13,
from montecarlo.cpp:7:
/usr/include/c++/7/bits/random.h:1818:2: note: candidate: std::uniform_real_distribution<_RealType>::result_type std::uniform_real_distribution<_RealType>::operator()(_UniformRandomNumberGenerator&, const std::uniform_real_distribution<_RealType>::param_type&) [with _UniformRandomNumberGenerator = std::linear_congruential_engine<long unsigned int, 48271, 0, 2147483647>; _RealType = long double; std::uniform_real_distribution<_RealType>::result_type = long double] <near match>
operator()(_UniformRandomNumberGenerator& __urng,
^~~~~~~~
/usr/include/c++/7/bits/random.h:1818:2: note: passing ‘const std::uniform_real_distribution<long double>*’ as ‘this’ argument discards qualifiers
有人知道这里有什么问题吗?
std::uniform_real_distrubution::operator()
不是常量成员函数,因此不能为常量实例调用:[rand.dist.uni.real]。
为什么它适用于Windows?微软的operator()
可能是const
,IIRC实施允许加强const
成员函数规范:http://eel.is/c++draft/member.functions#2。