$ time ./llil3vec-tbb-a big1.txt big2.txt big3.txt >f.tmp
llil3vec-tbb-a (fixed string length=6) start
use TBB
get_properties      CPU time : 2.9722 secs
emplace set sort    CPU time : 0.61156 secs
write stdout        CPU time : 0.828023 secs
total               CPU time : 4.41257 secs
total        wall clock time : 3 secs

real    0m2.552s
user    0m4.304s
sys     0m0.438s