Question

此源可以使用自定义顺序使用整数对向量的优先级队列：

std::vector < std::tuple < unsigned int, int, int > > targets_vector;


//   Related to 'thread_ticket' and 'targets_vector'. Useful as a
// pointer to a variable unique per thread.
// TODO   Not standard (__thread).
static __thread std::tuple < unsigned int, int, int > effective_target;


//   Related to 'effective_target' initialization. Useful as a boolean
// variable unique per thread.
// TODO   Not standard (__thread).
static __thread bool effective_target_filled = false;


struct NearerTarget
{
    bool operator()(
            const std::vector < std::pair < int, int > > & lhs,
            const std::vector < std::pair < int, int > > & rhs) const
    {
        std::pair < int, int > lhs_back = lhs.back();
        std::pair < int, int > rhs_back = rhs.back();
        if (effective_target_filled == false)
        {
            unsigned int i = 0;
            bool found = false;
            lock.lock();
            while (! found && i < targets_vector.size())
            {
                if (std::get<0>(targets_vector[i]) == thread_ticket)
                {
                    found = true;
                }
                else
                {
                    i++;
                }
            }
            lock.unlock();
            assert(found);
            effective_target = targets_vector[i];
            effective_target_filled = true;
        }
        int target_first = std::get<1>(effective_target);
        int target_second = std::get<2>(effective_target);
        unsigned int lhs_distance =
            std::abs(lhs_back.first - target_first) +
            std::abs(lhs_back.second - target_second);
        unsigned int rhs_distance =
            std::abs(rhs_back.first - target_first) +
            std::abs(rhs_back.second - target_second);

        return (lhs_distance > rhs_distance);
    }
};


int function(
        const int start_x, const int start_y, const int target_x,
        const int target_y)
{
    //   Generate a ticket.
    lock.lock();
    thread_ticket = tickets_so_far++;
    lock.unlock();

    //   Initialize data structure.
    std::pair < int, int > n_start (start_x, start_y);
    std::vector < std::pair < int, int > > starting_path (1, n_start);
    std::priority_queue <
        std::vector < std::pair < int, int > >,
        std::vector < std::vector < std::pair < int, int > > >,
        NearerTarget
    > active_paths;
    active_paths.push(starting_path);

    //   Initialize target pair.
    std::pair < int, int > n_target (target_x, target_y);

    //   Add target pair to the shared data structure.
    lock.lock();
    targets_vector.push_back(std::make_tuple(
            thread_ticket, n_target.first, n_target.second));
    lock.unlock();

    //   [...]
}

在尝试为优先级队列使用预分配器策略时遇到麻烦。如图所示， easy 至少比其他想要做的更容易预先分配std::vector < T >。但我没有得到预分配这种std::priority_queue < 3? >的语法。

//   Initialize data structure.
std::pair < int, int > n_start (start_x, start_y);
std::vector < std::pair < int, int > > starting_path (1, n_start);
//   Allocator container for the priority queue.
std::vector < unsigned char > pq_allocator;
pq_allocator.reserve(
        10 * (std::abs(start_x - target_x) +
            std::abs(start_y - target_y)));
//   Another argument for creating the preallocated priority queue.
NearerTarget nt;
std::priority_queue <
    std::vector < std::pair < int, int > >,
    std::vector < std::vector < std::pair < int, int > > >,
    NearerTarget
> active_paths(
        // std::less < unsigned char > (),
        nt,
        // std::move(
            pq_allocator
        // )
);

这让我得到了g++追踪：

find_path.cpp: In function ‘int FindPath(int, int, int, int, const unsigned cha
r*, int, int, int*, int)’:
find_path.cpp:215:5: error: no matching function for call to ‘std::priority_que
ue<std::vector<std::pair<int, int> >, std::vector<std::vector<std::pair<int, in
t> > >, NearerTarget>::priority_queue(NearerTarget&, std::vector<unsigned char>
&)’
    );
    ^
find_path.cpp:215:5: note: candidates are:
In file included from /usr/local/include/c++/4.8.4/queue:64:0,
                from find_path.cpp:12:
/usr/local/include/c++/4.8.4/bits/stl_queue.h:453:9: note: template<class _Inpu
tIterator> std::priority_queue<_Tp, _Sequence, _Compare>::priority_queue(_Input
Iterator, _InputIterator, const _Compare&, _Sequence&&)
        priority_queue(_InputIterator __first, _InputIterator __last,
        ^
/usr/local/include/c++/4.8.4/bits/stl_queue.h:453:9: note:   template argument 
deduction/substitution failed:
find_path.cpp:215:5: note:   deduced conflicting types for parameter ‘_InputIte
rator’ (‘NearerTarget’ and ‘std::vector<unsigned char>’)
    );
    ^
In file included from /usr/local/include/c++/4.8.4/queue:64:0,
                from find_path.cpp:12:
/usr/local/include/c++/4.8.4/bits/stl_queue.h:442:9: note: template<class _Inpu
tIterator> std::priority_queue<_Tp, _Sequence, _Compare>::priority_queue(_Input
Iterator, _InputIterator, const _Compare&, const _Sequence&)
        priority_queue(_InputIterator __first, _InputIterator __last,
        ^
/usr/local/include/c++/4.8.4/bits/stl_queue.h:442:9: note:   template argument 
deduction/substitution failed:
find_path.cpp:215:5: note:   deduced conflicting types for parameter ‘_InputIte
rator’ (‘NearerTarget’ and ‘std::vector<unsigned char>’)
    );
    ^
In file included from /usr/local/include/c++/4.8.4/queue:64:0,
                from find_path.cpp:12:
/usr/local/include/c++/4.8.4/bits/stl_queue.h:408:7: note: std::priority_queue<
_Tp, _Sequence, _Compare>::priority_queue(const _Compare&, _Sequence&&) [with _
Tp = std::vector<std::pair<int, int> >; _Sequence = std::vector<std::vector<std
::pair<int, int> > >; _Compare = NearerTarget]
      priority_queue(const _Compare& __x = _Compare(),
      ^
/usr/local/include/c++/4.8.4/bits/stl_queue.h:408:7: note:   no known conversio
--More--_

情况对你来说是否熟悉？有什么建议？有想法吗？

201510111727 UTC ：已编辑源和输出。

无法预先分配std :: priority_queue＆lt; std :: vector＆lt; T> ＆GT;

0 个答案: