$ time NUM_THREADS=4 ./rtoa-pgatram-openmp t1.txt t1.txt t1.txt t1.txt >s.tmp
use OpenMP
read_input_files  : 15996000 items
read file time    :    0.405 secs
roman_to_dec time :    0.568 secs
total time        :    0.974 secs

real    0m0.995s
user    0m1.439s
sys     0m0.539s

$ cmp f.tmp s.tmp