When rdft < 1e-12, it does not apply the filter. The user should be either notified when this condition is anticipated when reading the parameter or the run should be terminated.

but0 was defined as the \int <gx,gy,gz> \cdot <ub,vb,wb> tb d\Omega
but now is defined with the direction theta with a unit vector

The new definition is redundant since a linear combination of but0_x and but0_y (without the gx,gy scaling) can be used in the online mode and the old definition can be restored.

They have been tagged with ! TODO in time.f

Create a document that briefly explains the content of each .f files in code/

Add subroutines that apply H-inverse to error terms in order to form the Riesz representations with H-norm.

There is a residual code that seems to be case-specific. If possible, this should be moved to a usr file or generalized so more broad class of cases can be handled.

These should be separated

https://github.com/kent0/MOR/projects/1#card-43834574

Add binvb subroutine for consistency

Please see https://github.com/kent0/NekMOR/runs/3633881197