Lengthen the last subcycle timestep to avoid very small dt #701
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Due to roundoff issues, it is possible for the current algorithm to divide the main timestep into N smaller dt's that, when summed up, so not exactly equal the desired target time. We already have protection against the case where the final time is slightly larger than the target time (in which case we shortened that timestep) but we had no protection against the case where we would end up slightly short of the target time, in which case we'd have to take a very short last timestep. This PR resolves that issue by making that last timestep slightly longer.
zingale
approved these changes
Nov 29, 2019
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PR summary
Due to roundoff issues, it is possible for the current algorithm to divide the main timestep into N smaller dt's that, when summed up, so not exactly equal the desired target time. We already have protection against the case where the final time is slightly larger than the target time (in which case
we shortened that timestep) but we had no protection against the case where we would end up slightly short of the target time, in which case we'd have to take a very short last timestep. This PR resolves that issue by making that last timestep slightly longer.
PR checklist
CHANGESfile has been updated