IMPORTANT:

Make sure you set the Gromacs build type to "Reference" when generating
or updating the reference values for any tests.

This is a shortcut to turn off GPU support, OpenMP support, MPI and
ThreadMPI, all CPU acceleration, we disable software invsqrt, fftpack
is used as the FFT library, and we set the compiler flags to "-O0 -g".
Currently we also prefer that you use gcc-7 as your compiler. These
details are all set up in cmake/gmxBuildTypeReference.cmake and that is
the primary source for questions about what comprises a reference build
of GROMACS.

This does not imply that other compilers or optimized/parallel versions
of GROMACS are less accurate (in fact, in some cases the opposite can be true),
but it is meant to provide a specification that is easier to go back and
compare with if we have bugs that are difficult to trace. 

Each regression test directory should contain reference log files where
the exact build options, compiler, and hardware used is specified.

