$ 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 :    0.321 secs
sort properties     time :    0.268 secs
vector reduce       time :    0.078 secs
vector stable sort  time :    0.194 secs
write stdout        time :    0.329 secs
total               time :    1.192 secs