Sorting a std::vector<std::pair<std::string, int> > is very slow because
std::swap is not used for switching strings.
std::swap for every std::pair should use two std::swap for the components of
the pair.
The following test program shows that this is currently not the case:
#include <iostream>
#include <algorithm>
#include <vector>
class A {
public:
A(int a) : val(a) { std::cout << "Constructing with: " << a << "\n"; }
A(A const & a) : val(a.val) { std::cout << " Copy constructor from: " <<
a.val << "\n"; }
A & operator=(A const & a) { val = a.val; std::cout << "Assignment from: "
<< a.val << "\n"; return *this; }
~A() { std::cout << "Destructing " << val << "\n";}
public:
int val;
};
namespace std {
void swap(A & a, A & b) {
std::cout << "SWapping: " << a.val << "/" << b.val << "\n";
std::swap(a, b);
}
}
int main() {
std::pair<A, int> f(A(10), 2);
std::pair<A, int> s(A(20), 3);
std::swap(f, s);
}
--
Summary: std::swap does not use std::swap for the components of a
std::pair
Product: gcc
Version: 4.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: bartoschek at gmx dot de
GCC build triplet: i586-suse-linux
GCC host triplet: i586-suse-linux
GCC target triplet: i586-suse-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38466
