[MITgcm-devel] vectorizing seaice and exf

[Martin Losch]

Hi,

the seaice model is now basically vectorizing quite well: with my  
(really: Jens-Olaf's) fix you improve the Vector operation ratio from  
91% to 99.4%, the most unsatifactory part remains in  
seaice_advection, where I can get only 84%, but I guess you cannot  
change that (gad_advection should have a similar problem).

The bottleneck (from a vectorization point of view) is in  
exf_bulkformulae (and exf_bulk_largeyeager04, I expect), because of  
the iteration as the innermost loop. Jens-Olaf's solution is  
unsatifactory: he noticed that niter_bulk = 2 always (per parameter  
definition) and just copied the loop body twice, thus removing the  
iteratioin loop. I am still looking for a directive that can do that  
automatically, since the loop range is know at compile time. But I am  
afraid that the only real solution would be "loop pushing": move the  
iteration out of the ij-loops. This means redefining a few fields  
(the ones that are updated in the iteration, which are they?) as 2D.

I would like to do this, but what's the best way: have two versions  
of exf_bulkformlulae, one as it is and one for vector machines? Or  
can we live with one version that is vectorizable at the cost of  
having a few extra 2d fields?

Martin