vector <bool>访问

Question

我使用gprof和报告来描述我的代码,大多数,如果不是所有前20个左右的东西都是关于向量的

Flat profile:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
 14.71      0.05     0.05  3870399     0.00     0.00  std::vector<bool, std::allocator<bool> >::size() const
 11.76      0.09     0.04 10552897     0.00     0.00  std::_Bit_reference::_Bit_reference(unsigned long*, unsigned long)
 11.76      0.13     0.04  7890323     0.00     0.00  std::_Bit_const_iterator::_Bit_const_iterator(std::_Bit_iterator const&)
  5.88      0.15     0.02 10089215     0.00     0.00  std::_Bit_iterator::operator*() const
  5.88      0.17     0.02  6083600     0.00     0.00  std::vector<bool, std::allocator<bool> >::operator[](unsigned int)
  5.88      0.19     0.02  3912611     0.00     0.00  std::vector<bool, std::allocator<bool> >::end() const
  5.88      0.21     0.02                             std::istreambuf_iterator<char, std::char_traits<char> > std::num_get<char, std::istreambuf_iterator<char, std::char_traits<char> > >::_M_extract_int<unsigned long long>(std::istreambuf_iterator<char, std::char_traits<char> >, std::istreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, std::_Ios_Iostate&, unsigned long long&) const
  2.94      0.22     0.01  6523499     0.00     0.00  std::_Bit_reference::operator bool() const
  2.94      0.23     0.01  3940406     0.00     0.00  std::vector<bool, std::allocator<bool> >::begin() const
  2.94      0.24     0.01  2807828     0.00     0.00  std::_Bit_iterator::operator++()
  2.94      0.25     0.01   146917     0.00     0.00  std::_Bit_iterator_base::_M_incr(int)
  2.94      0.26     0.01   121706     0.00     0.00  std::__miter_base<unsigned long*, false>::__b(unsigned long*)
  2.94      0.27     0.01    46008     0.00     0.00  std::_Bvector_base<std::allocator<bool> >::~_Bvector_base()
  2.94      0.28     0.01    22596     0.00     0.00  std::_Bit_iterator std::__copy_move<false, false, std::random_access_iterator_tag>::__copy_m<std::_Bit_iterator, std::_Bit_iterator>(std::_Bit_iterator, std::_Bit_iterator, std::_Bit_iterator)
  2.94      0.29     0.01     4525     0.00     0.05  integer::operator+(integer)
  2.94      0.30     0.01     1382     0.01     0.01  void std::_Destroy<unsigned int*, unsigned int>(unsigned int*, unsigned int*, std::allocator<unsigned int>&)
  2.94      0.31     0.01                             std::string::size() const
  2.94      0.32     0.01                             std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()
  2.94      0.33     0.01                             std::locale::locale()
  2.94      0.34     0.01                             __dynamic_cast

这是一个好兆头,因为它意味着我的其余函数非常有效,或者从向量<bool>访问值真的很慢？

我用gcc -std = c ++ 0x编译

Answer 1

vector<bool>不存储bools.它基本上是一个位域.你需要付出代价才能修改单个值.

如果考虑运行时性能,请考虑vector<char>或deque<bool>改为.