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

Guillaume Chevrot guillaume.chevrot at gmail.com
Fri Oct 11 19:58:45 CEST 2013

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



*PS: I am not the only one encountering this behavior. In the literature,
this problem has already been mentioned:

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