[gmx-users] energy drift - comparison of double and single precision

[Guillaume Chevrot]

Hi all,

I recently compared the total energy of 2 simulations:
lysozyme in water / NVE ensemble / single precision
lysozyme in water / NVE ensemble / double precision

... and what I found was quite ... disturbing (see the attached figure -
plots of the total energy). I observe a constant drift in energy in the
case of the single precision simulation.

Did I do something wrong*? Any remarks are welcomed! I join the ‘mdout.mdp’
file so you can check what mdp options I used.

My second question is: if I did not do something wrong, what are the
consequences on the simulation? Can I trust the results of single precision
simulations?

Regards,

Guillaume

*PS: I am not the only one encountering this behavior. In the literature,
this problem has already been mentioned:
http://jcp.aip.org/resource/1/jcpsa6/v126/i4/p046101_s1