time: cannot run ./garescorer: No such file or directory
To take advantage of multiple CPU cores, use pgapack-mpi (which appears to be broken on ubuntu), and run it as:
mpirun -np 4 ./garescorer -b 10 -e 5500 -t 5.0
Replace "4" with your number of CPU cores. Although it looks like this causes redundant processing instead of distributed load.