$ time ./llil2grt big1.txt big2.txt big3.txt >out.txt
llil2grt start
get_properties      CPU time : 3.55473 secs
emplace set sort    CPU time : 0.998423 secs
write stdout        CPU time : 0.854453 secs
total               CPU time : 5.40764 secs
total        wall clock time : 5 secs

real  0m5.973s
user  0m5.697s
sys   0m0.292s

$ NUM_THREADS=1 ./llil4map-no6-uno big1.txt big2.txt big3.txt >out.txt
llil4map start
use std::unordered_map
don't use OpenMP
use boost sort
get properties         3.368 secs
finish merging         1.202 secs
vector stable sort     0.898 secs
write stdout           0.261 secs
total time             5.730 secs

$ NUM_THREADS=1 ./llil4map-no6-std big1.txt big2.txt big3.txt >out.txt
llil4map start
use std::map
don't use OpenMP
use boost sort
get properties         3.328 secs
finish merging         0.657 secs
vector stable sort     0.816 secs
write stdout           0.268 secs
total time             5.069 secs

$ NUM_THREADS=1 ./llil4map-no6-flat big1.txt big2.txt big3.txt >out.txt
llil4map start
use phmap::parallel_flat_hash_map
don't use OpenMP
use boost sort
get properties         1.565 secs
map to vector          0.200 secs
vector stable sort     0.665 secs
write stdout           0.220 secs
total time             2.652 secs