$ NUM_THREADS=6 ./llil4vec-tbb big1.txt big2.txt big3.txt >f.tmp
llil4vec-tbb (fixed string length=6) start
use TBB
get properties      time : 0.399307 secs
sort properties     time : 0.277303 secs
emplace set sort    time : 0.764016 secs
write stdout        time : 0.51597 secs
total               time : 1.95691 secs