Correct the equation for the entropy time derivative in GADGET2_SPH
This fixes #183 (closed) meaning that energy is now correctly conserved.
It also:
- Adds a parameter file and run script for the perturbed box test case.
- Adds entropy to the diagnostics file.
- Replace the MPI_AllReduce in the statistics collection by an MPI_Reduce since only rank 0 writes anyway.
- Gives a better documentation for the
approx_exp()
function. - Adds an accuracy test for the approximate maths functions (currently only exp())
- Adds a test no make sure the symmetric and non-symmetric versions of the SPH interaction routines give the same answer. That was the origin of the energy non-conservation bug.