$ NUM_THREADS=3 ./llil4vec big1.txt big2.txt big3.txt >out.txt
llil4vec (fixed string length=12) start
use OpenMP
use boost sort
get properties         0.131 secs
sort properties        0.191 secs
vector reduce          0.036 secs
vector stable sort     0.267 secs
write stdout           0.191 secs
total time             0.818 secs