Overset performance degradation
We have been monitoring the performance of the overset solvers hoping in some performance in the new releases but it looks like they actually worsened starting from the v1706 and now further degraded in the latest v1812.
The following results (cloclTime per 2sec of simulated time on 1 core) are based on the twoSimpleRotors test case, run with the fixed time step and using the same fvSolution, fvSchemes and dynamicMeshDict in each case:
v1706: 683 sec v1806: 860 sec v1812: 5024 sec
Note that the v1812 needs about twice the number of iterations per correctors, but doesn't justify such an increase in the total clock time.
Also, when using the v1812 with the original settings, the clock time increases to about 13.000 sec.
Would be nice to have a little bit of feedback and some directions to perform further testing and hopefully improve the usage of overset in general.
## Reattaching the author to the issue ticket: @Ricky-11 ##