I am copying the round-off level changes made to grid weights and grid interpolation functions from the generalized_grid branch over to the master branch. This is being done ahead of merging code from the master over to the generalized_grid branch.
This code is necessary to get results in the generalized grid branch bit-for-bit between ascending and descending grid directions when optimization is set to -O0.
This change produces changes at the numerical round-off level in the affected calculations, making this commit BIT_CHANGING.
Plots show lines overlap for almost all cases besides the most sensitive cases (ARM 97, TWP ICE, etc. -- looking at those shows you how much of a difference a simple numerical round-off can make).