Benchmarks are compiled with -O2 and debug options

This issue simply asks for a clarification (I can not add a label like "documentation issue" myself).

In the benchmarks's Makefile, one can find:

FLASFFPACK_CXXFLAGS =  -O2 -march=native -Wall -DNDEBUG -UDEBUG

Is there a reason to compile with -O2 and not with -O3?

Are the -DNDEBUG and -UDEBUG necessary flags? May it hinder performance?

Provide feedback