In previous versions of CPPTRAJ, the direct space term (both regular Ewald and PME) had a bug where some interactions at the edge of the cell were being erroneously discarded for smaller unit cells (6 or fewer grid cells in any axis) as redundant when they were in fact not. This resulted in some interactions (but not all due to some being outside the cutoff) being missed for these cells. The existing tests of small cells did not catch it since the discarded interactions were outside the cutoff (this is why there are no changes to the current saved test output).
This PR fixes the direct space sum for these smaller unit cells.
Version 6.20.0.
In previous versions of CPPTRAJ, the direct space term (both regular Ewald and PME) had a bug where some interactions at the edge of the cell were being erroneously discarded for smaller unit cells (6 or fewer grid cells in any axis) as redundant when they were in fact not. This resulted in some interactions (but not all due to some being outside the cutoff) being missed for these cells. The existing tests of small cells did not catch it since the discarded interactions were outside the cutoff (this is why there are no changes to the current saved test output).
This PR fixes the direct space sum for these smaller unit cells.