为什么在这个omp_declare_reduction中出现这个错误？

Question

我有这个文件：

A.H

struct B; 

struct A 
{ 
    A(... B &b) : 
     b(b) {} 

    B &b; 
}; 

而且B.h：

#include "A.h" 
struct B{ 
... 
std::vector<A> as; 
} 

而且我有这个omp_declare_reduction：

#pragma omp declare reduction(merge : B : omp_out.as.insert(omp_out.as.end(), omp_in.as.begin(), omp_in.as.end())) 

不过，我得到这个错误（其中A=FindAffineShapeArgs和B=Wrapper）：

/usr/include/c++/5/bits/stl_algobase.h(564): error: function "FindAffineShapeArgs::operator=(const FindAffineShapeArgs &)" (declared implicitly) cannot be referenced -- it is a deleted function 
     *--__result = std::move(*--__last); 
        ^
      detected during: 
      instantiation of "_BI2 std::__copy_move_backward<true, false, std::random_access_iterator_tag>::__copy_move_b(_BI1, _BI1, _BI2) [with _BI1=FindAffineShapeArgs *, _BI2=FindAffineShapeArgs *]" at line 606 
      instantiation of "_BI2 std::__copy_move_backward_a<_IsMove,_BI1,_BI2>(_BI1, _BI1, _BI2) [with _IsMove=true, _BI1=FindAffineShapeArgs *, _BI2=FindAffineShapeArgs *]" at line 615 
      instantiation of "_BI2 std::__copy_move_backward_a2<_IsMove,_BI1,_BI2>(_BI1, _BI1, _BI2) [with _IsMove=true, _BI1=FindAffineShapeArgs *, _BI2=FindAffineShapeArgs *]" at line 686 
      instantiation of "_BI2 std::move_backward(_BI1, _BI1, _BI2) [with _BI1=FindAffineShapeArgs *, _BI2=FindAffineShapeArgs *]" at line 636 of "/usr/include/c++/5/bits/vector.tcc" 
      instantiation of "void std::vector<_Tp, _Alloc>::_M_range_insert(std::vector<_Tp, _Alloc>::iterator, _ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with _Tp=FindAffineShapeArgs, _Alloc=std::allocator<FindAffineShapeArgs>, _ForwardIterator=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>]" at line 1377 of "/usr/include/c++/5/bits/stl_vector.h" 
      instantiation of "void std::vector<_Tp, _Alloc>::_M_insert_dispatch(std::vector<_Tp, _Alloc>::iterator, _InputIterator, _InputIterator, std::__false_type) [with _Tp=FindAffineShapeArgs, _Alloc=std::allocator<FindAffineShapeArgs>, _InputIterator=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>]" at line 1100 of "/usr/include/c++/5/bits/stl_vector.h" 
      instantiation of "std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(std::vector<_Tp, _Alloc>::const_iterator, _InputIterator, _InputIterator) [with _Tp=FindAffineShapeArgs, _Alloc=std::allocator<FindAffineShapeArgs>, _InputIterator=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>, <unnamed>=void]" at line 345 of 
         "/home/luca/Dropbox/HKUST/CloudCache/cloudcache/CloudCache/Descriptors/hesaff/pyramid.cpp" 

    /usr/include/c++/5/bits/stl_algobase.h(340): error: function "FindAffineShapeArgs::operator=(const FindAffineShapeArgs &)" (declared implicitly) cannot be referenced -- it is a deleted function 
       *__result = *__first; 
         ^
       detected during: 
       instantiation of "_OI std::__copy_move<false, false, std::random_access_iterator_tag>::__copy_m(_II, _II, _OI) [with _II=FindAffineShapeArgs *, _OI=FindAffineShapeArgs *]" at line 402 
       instantiation of "_OI std::__copy_move_a<_IsMove,_II,_OI>(_II, _II, _OI) [with _IsMove=false, _II=FindAffineShapeArgs *, _OI=FindAffineShapeArgs *]" at line 440 
       instantiation of "_OI std::__copy_move_a2<_IsMove,_II,_OI>(_II, _II, _OI) [with _IsMove=false, _II=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>, _OI=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>]" at line 472 
       instantiation of "_OI std::copy(_II, _II, _OI) [with _II=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>, _OI=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>]" at line 637 of "/usr/include/c++/5/bits/vector.tcc" 
       instantiation of "void std::vector<_Tp, _Alloc>::_M_range_insert(std::vector<_Tp, _Alloc>::iterator, _ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with _Tp=FindAffineShapeArgs, _Alloc=std::allocator<FindAffineShapeArgs>, _ForwardIterator=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>]" at line 1377 of "/usr/include/c++/5/bits/stl_vector.h" 
       instantiation of "void std::vector<_Tp, _Alloc>::_M_insert_dispatch(std::vector<_Tp, _Alloc>::iterator, _InputIterator, _InputIterator, std::__false_type) [with _Tp=FindAffineShapeArgs, _Alloc=std::allocator<FindAffineShapeArgs>, _InputIterator=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>]" at line 1100 of "/usr/include/c++/5/bits/stl_vector.h" 
       instantiation of "std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(std::vector<_Tp, _Alloc>::const_iterator, _InputIterator, _InputIterator) [with _Tp=FindAffineShapeArgs, _Alloc=std::allocator<FindAffineShapeArgs>, _InputIterator=__gnu_cxx::__normal_iterator<FindAffineShapeArgs *, std::vector<FindAffineShapeArgs, std::allocator<FindAffineShapeArgs>>>, <unnamed>=void]" at line 345 of 
          "/home/luca/Dropbox/HKUST/CloudCache/cloudcache/CloudCache/Descriptors/hesaff/pyramid.cpp" 

    compilation aborted for /home/luca/Dropbox/HKUST/CloudCache/cloudcache/CloudCache/Descriptors/hesaff/pyramid.cpp (code 2) 

为什么出现这种情况？这可能与this有关，但用于其他情况。

Answer 1

这与omp无关，或者表观循环参考（您的循环参考本身，这里没有任何错误）。你会得到一个类似的编译错误有：

#include <vector> 

struct B {}; 

struct A 
{ 
    A(B &b) : 
     b(b) {} 

    B &b; 
}; 


B b; 
A a{b}, aa{b}; 

void foo() 
{ 
     a=aa; 
} 

GCC错误的消息，在THID的情况下，将指向您的线索：

t.C:19:4: error: use of deleted function ‘A& A::operator=(const A&)’ 

包含引用类没有默认的赋值运算符。这是因为传统意义上的参考文献无法更改或“分配给”。

您正在创建一个std::vector，需要时根据需要复制/移动其值。但是矢量的类包含一个引用成员，它从高轨道上对类的赋值运算符进行核武。

为了做到这一点，你需要定义自己的赋值运算符和/或拷贝构造函数为A类，并让他们做什么，你需要他们做。