$ NUM_THREADS=6 ./llil4vec2 big1.txt big2.txt big3.txt >f.tmp
llil4vec2 (fixed string length=6) start
use OpenMP
use boost sort
get properties      time :    0.353 secs
sort properties     time :    0.271 secs
vector reduce       time :    0.074 secs
vector stable sort  time :    0.197 secs
write stdout        time :    0.322 secs
total               time :    1.219 secs