[Mitgcm-support] Re: Why are some variables in COMMON when they are only used once

[mitgcm-support at dev.mitgcm.org]

Hmmm.....

No thats odd in that you can't do an exchange within a
bi,bj loop. 

Jean-Michel - q'est qui ce passe?

Chris
Patrick Heimbach wrote:
> 
> Is this related to the fact that the bi,bj loops
> appear OUTSIDE of calc_exact_eta?
> Otherwise, the block in forward_step
> 
>         DO bj=myByLo(myThid),myByHi(myThid)
>          DO bi=myBxLo(myThid),myBxHi(myThid)
>            CALL CALC_EXACT_ETA( .FALSE., bi,bj, uVel,vVel,
>      I                          startTime, nIter0, myThid )
>          ENDDO
>         ENDDO
> 
> appears a bit strange
> (I would have put the bi,bj loops inside CALC_EXACT_ETA).
> If they are inside, I may be able to fix the TAF problem
> by some HPF directives without having to remove the "common".
> 
> P.
> 
> Chris Hill wrote:
> >
> > Common blocks are used to force otherwise local variables
> > into global storage. This allows multi-threaded exchange operations
> > to work.
> >
> > If you don't want multi-threaded parallelism then you can remove the
> > common block.
> >
> > Patrick Heimbach wrote:
> > >
> > > Jean-Michel,
> > >
> > > in calc_exact_eta the field hDivFlow is declared
> > > in a common block.
> > > However, that common block is - I think-  nowhere else needed.
> > > Furthermore, TAF gets totally confused by it, I have no clue, why.
> > > Can I just remove the common block?
> > >
> > > P.
> > > --
> > > _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> > >
> > > Patrick Heimbach ........................ FON: +1/617/253-5259
> > > Massachusetts Institute of Technology ... FAX: +1/617/253-4464
> > > EAPS, Room 54-1518 ...........................................
> > > 77 Massachusetts Avenue .............. mailto:heimbach at mit.edu
> > > Cambridge MA 02139, U.S.A. ..... http://www.mit.edu/~heimbach/
> 
> --
> _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> 
> Patrick Heimbach ........................ FON: +1/617/253-5259
> Massachusetts Institute of Technology ... FAX: +1/617/253-4464
> EAPS, Room 54-1518 ...........................................
> 77 Massachusetts Avenue .............. mailto:heimbach at mit.edu
> Cambridge MA 02139, U.S.A. ..... http://www.mit.edu/~heimbach/