Stat dumping segfault

[kavon]

Happens in aebf52bf and the prior commit. Non-debug stack trace:

Thread 1 "matmul" received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x00007ffff7bae3a0 in tuner::Feedback::betterThan(tuner::Feedback&) () from /home/kavon/anl/atJIT/install/lib/libEasyJitRuntime.so
#2  0x00007ffff7bac7f4 in void std::__introsort_loop<__gnu_cxx::__normal_iterator<unsigned long*, std::vector<unsigned long, std::allocator<unsigned long> > >, long, __gnu_cxx::__ops::_Iter_comp_iter<tuner::Tuner::dumpStats(std::ostream&) const::S> >(__gnu_cxx::__normal_iterator<unsigned long*, std::vector<unsigned long, std::allocator<unsigned long> > >, __gnu_cxx::__normal_iterator<unsigned long*, std::vector<unsigned long, std::allocator<unsigned long> > >, long, __gnu_cxx::__ops::_Iter_comp_iter<tuner::Tuner::dumpStats(std::ostream&) const::S>) ()
   from /home/kavon/anl/atJIT/install/lib/libEasyJitRuntime.so
#3  0x00007ffff7bac827 in void std::__introsort_loop<__gnu_cxx::__normal_iterator<unsigned long*, std::vector<unsigned long, std::allocator<unsigned long> > >, long, __gnu_cxx::__ops::_Iter_comp_iter<tuner::Tuner::dumpStats(std::ostream&) const::S> >(__gnu_cxx::__normal_iterator<unsigned long*, std::vector<unsigned long, std::allocator<unsigned long> > >, __gnu_cxx::__normal_iterator<unsigned long*, std::vector<unsigned long, std::allocator<unsigned long> > >, long, __gnu_cxx::__ops::_Iter_comp_iter<tuner::Tuner::dumpStats(std::ostream&) const::S>) ()
   from /home/kavon/anl/atJIT/install/lib/libEasyJitRuntime.so
#4  0x00007ffff7ba523b in tuner::Optimizer::dumpStats(std::basic_ofstream<char, std::char_traits<char> >&) const () from /home/kavon/anl/atJIT/install/lib/libEasyJitRuntime.so
#5  0x000000000040dfba in tuner::ATDriver::exportStats(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >) ()
#6  0x0000000000406bdd in tuner::ATDriver::exportStats() ()
#7  0x0000000000403d97 in testWith(tuner::AutoTuner, int) ()
#8  0x0000000000403e49 in main ()