A student in our group found that using rerun in GROMACS 2019, neither the Coulomb nor the LJ reciprocal terms are recalculated. These energies are 0, and consequently, the **potential energy is missing these terms and is off compared to the original run**. The bug can be retraced to \#1868, where rerun was split off and restricted to explicitly only calculate forces and potential energies, omitting kinetic energies, virial, pressure, constraints, etc. Consequently, within do\_rerun, do\_force did not get the `GMX_FORCE_VIRIAL` flag anymore. In `gmx_pme_do`, called from the lower level functions within do\_force, the reciprocal terms are however only calculated if `GMX_FORCE_VIRIAL` was originally passed. I don’t see a compelling reason why reciprocal energy terms and virial should be intimately linked, but maybe I’m overlooking a detail here. Note that due to \#2649, the `GMX_FORCE_VIRIAL` flag was reintroduced if GROMACS was compiled with GPU support, so GPU enabled builds are not affected by this bug. The easy solution to fix this bug is to pass `GMX_FORCE_VIRIAL` in all cases. Moving forward, we should check whether these options can be disentangled. *(from redmine: issue id 3400, created on 2020-02-25 by ptmerz, closed on 2020-02-28)* * Relations: * relates #1868 * relates #2649 * Changesets: * Revision cc055a76cac976ba56ed9fb8607aeb885a533d28 on 2020-02-26T02:15:09Z: ``` Fix calculation of reciprocal terms in rerun This at least temporarily fixes #3400. Change-Id: I04d67d9bb3edbd66049573de71940e4bb7fa1ad4 ```