Question

我想使用多个线程插入bimap。我尝试了以下代码：

parallel_index.cpp

#include <iostream>
#include <string>
#include <algorithm>
#include <thread>
#include <mutex>
#include <boost/bimap.hpp>
#include <boost/bimap/unordered_set_of.hpp>
#include <boost/bimap/unordered_multiset_of.hpp>
#include "parallel_index.h"


namespace bimaps = boost::bimaps;
typedef boost::bimap<bimaps::unordered_set_of<uint64_t>,
        bimaps::unordered_multiset_of<std::string> > bimap_reference;
typedef bimap_reference::value_type position;
bimap_reference reference_index_vector;


size_t total_threads = std::thread::hardware_concurrency();

std::string sequence_content = "ABCDDBACDDDCBBAAACBDAADCBDAAADCBDADADACBDDCBBBCDCBCDAADCBBCDAAADCBDA";
uint64_t sequence_length = sequence_content.length();
int split = 5;
uint64_t erase_length = 0;
unsigned int seq_itr = 0;

std::mutex mtx;   // to protect against concurent access
int main(){
    thread_test::create_index index;
    std::thread threads[total_threads-1];

    for(unsigned int i = 0; i < total_threads; i++){
        threads[i] = std::thread(&thread_test::create_index::reference_index_hash, std::ref(index), sequence_length, split, sequence_content, erase_length);
    }

    for(unsigned int i = 0; i < total_threads; i++){
        threads[i].join();
    }
}



/*
 * Creating index
 */
void thread_test::create_index::reference_index_hash(uint64_t &sequence_length, int &split,
        std::string &sequence_content, uint64_t &erase_length  ){

    for (; seq_itr < sequence_length; ++seq_itr ){
        std::string splitstr = sequence_content.substr(erase_length, split);

        std::lock_guard<std::mutex> lck(mtx);
        reference_index_vector.insert(position(seq_itr, splitstr));
        seq_itr += split-1;
        erase_length += split;


// the length of test is very large so erase some text
        if(erase_length > 10000){ 
            sequence_content.erase(0,erase_length);
            erase_length = 0;
        }
    }


//  for( bimap_reference::const_iterator iter = reference_index_vector.begin(), iend = reference_index_vector.end();
//          iter != iend; ++iter ) {
//      std::cout << iter->left << " <--> "<< iter->right <<std::endl;
//  }

}

parallel_index.h

#ifndef PARALLEL_INDEX_H_
#define PARALLEL_INDEX_H_


#include<iostream>
#include <algorithm>
#include <utility>
#include <boost/bimap.hpp>
#include <boost/bimap/unordered_set_of.hpp>
#include <boost/bimap/unordered_multiset_of.hpp>




//typedef boost::unordered_map<int, std::pair<int, unsigned long int>& > reference_map;

namespace bimaps = boost::bimaps;

typedef boost::bimap<bimaps::unordered_set_of<uint64_t>,
        bimaps::unordered_multiset_of<std::string > > bimap_reference;
typedef bimap_reference::value_type position;
extern bimap_reference reference_index_vector;


namespace thread_test{

class create_index{
public:
    void reference_index_hash(uint64_t &sequence_length, int &split,
            std::string &sequence_content, uint64_t &erase_length);
};
}


#endif /* PARALLEL_INDEX_H_ */

我使用eclipse IDE编译代码，但是我得到了错误

g++ -std=c++17 -I/home/ahussain/boost_1_65_1 -O3 -Wall -c -fmessage-length=0 -MMD -MP -MF"parallel_index.d" -MT"parallel_index.o" -o "parallel_index.o" "../parallel_index.cpp"
In file included from /usr/include/c++/5/thread:39:0,
                 from ../parallel_index.cpp:13:
/usr/include/c++/5/functional: In instantiation of ‘struct std::_Bind_simple<std::_Mem_fn<void (thread_test::create_index::*)(long unsigned int&, int&, std::__cxx11::basic_string<char>&, long unsigned int&)>(std::reference_wrapper<thread_test::create_index>, long unsigned int, int, std::__cxx11::basic_string<char>, long unsigned int)>’:
/usr/include/c++/5/thread:137:59:   required from ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (thread_test::create_index::*)(long unsigned int&, int&, std::__cxx11::basic_string<char>&, long unsigned int&); _Args = {std::reference_wrapper<thread_test::create_index>, long unsigned int&, int&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&, long unsigned int&}]’
../parallel_index.cpp:42:149:   required from here
/usr/include/c++/5/functional:1505:61: error: no type named ‘type’ in ‘class std::result_of<std::_Mem_fn<void (thread_test::create_index::*)(long unsigned int&, int&, std::__cxx11::basic_string<char>&, long unsigned int&)>(std::reference_wrapper<thread_test::create_index>, long unsigned int, int, std::__cxx11::basic_string<char>, long unsigned int)>’
       typedef typename result_of<_Callable(_Args...)>::type result_type;
                                                             ^
/usr/include/c++/5/functional:1526:9: error: no type named ‘type’ in ‘class std::result_of<std::_Mem_fn<void (thread_test::create_index::*)(long unsigned int&, int&, std::__cxx11::basic_string<char>&, long unsigned int&)>(std::reference_wrapper<thread_test::create_index>, long unsigned int, int, std::__cxx11::basic_string<char>, long unsigned int)>’
         _M_invoke(_Index_tuple<_Indices...>)
         ^
subdir.mk:18: recipe for target 'parallel_index.o' failed
make: *** [parallel_index.o] Error 1

我看了http://jsbin.com/jucosalice/edit?html,output，但无法逃脱错误。

Answer 1

index可以作为简单指针而不是包装引用传递，但其余变量应该是引用，因此它们需要std::ref处理。

换句话说

threads[i] = std::thread(&thread_test::create_index::reference_index_hash,
                         &index,
                         std::ref(sequence_length),
                         std::ref(split),
                         std::ref(sequence_content),
                         std::ref(erase_length));

将编译。

但是...

不幸的是，这意味着您将有多个线程都使用相同的变量。这通常是非启动的，因为线程将同时访问并对变量存储的值造成严重破坏。您将不得不重新考虑如何使用这些变量并按值传递它们或找到更好的方法来隔离或保护它们。

和...

std::thread threads[total_threads-1];

结合

for(unsigned int i = 0; i < total_threads; i++)

将导致进入数组的thread太多total_threads。 0到total_threads的计数为thread total_threads-1，而不是{{1}}。

线程插入bimap

1 个答案: