3.3.1. make options

The default compiler options for gfortran and ifort are chosen as a compromise between compile time and performance; they generally give close to optimal performance, so are suitable for shorter runs and for development.

To get the best performance, compile with make clean; make OPTS=optimized, which typically gives a gain of a few percent in performance, at the cost of increased compilation time.

If the code crashes, try recompiling with make clean; make OPTS=full_debug or make clean; make OPTS=debug. The first provides comprehensive debug settings, while impacting performance significantly, while the 2nd avoids the particular options that impact performance the most.

The make clean part is only needed the 1st time after changing OPTS bundle