$ g++ -o rtoa-pgatram -std=c++20 -Wall -O3 rtoa-pgatram.cpp
$ ./rtoa-pgatram t1.txt >cpp.tmp
read_input_file   : 3999000 items
read file time    :    0.264 secs
roman_to_dec time :    0.095 secs
output time       :    0.247 secs
$ diff roman.tmp cpp.tmp