$ g++ -Wall -Wextra PID_test.cpp Arduino.cpp Arduino-PID-Library/PID_v1.cpp -o PID_test$ ./PID_test 010070.000000$
There is some simple PID code in this link.
It may be easier to adapt for the RPi.
Much simpler, misses most of the features implemented by by Brett.
I already adapted it, see the commit link in previous posting, was easy and works.