[MITgcm-devel] KPP and smoothing

[Dimitris Menemenlis]

Hi Natacha, the smoothing options for KPP are there to get rid of a grid-scale 
computational mode.  Default smoothing options in KPP_OPTIONS.h is what I 
recommend that you use.

KPP_REACTIVATE_OL4 appears to be an adjoint-related flag that Patrick put in six 
years and two months ago.  It probably should not be there.  I am not sure.

There is a KPP_OPTIONS.h flag that allows you to get rid of the requirement for 
increased overlap: #define FRUGAL_KPP

C o When set, use exchange calls rather than recomputation
C   to obtain KPP parameters in overlap region.  This option
C   was added to reduce stack size requirements on the
C   Origin 2000.  It decreases memory and computation
C   requirements at the expense of increased communications.
C   For a 64-processor 360x224x46 MPI configuration on the
C   Exemplar or Origin 2000, wall clock time is about the
C   same whether FRUGAL_KPP is turned on or off.

You can experiment to see which is faster for your setup, i.e., recomputation or 
increased overlap.

Dimitris