[MITgcm-devel] Re: TARGET_NEC_SX in ini_curvilinear_grid.F

[Jean-Michel Campin]

I only realised now that I send this to support list instead of devel.
Sorry.
Jean-Michel

On Thu, Feb 12, 2009 at 04:05:56PM -0500, Jean-Michel Campin wrote:
> Hi Martin,
> 
> I am still thinking that if there is a problem in mom_calc_visc.F
> it should be fixed, and don't see what is wrong with the exch S/R.
> 
> I have options for 2 compilers (gfortran & ifort) that make the run
> to stop when a division by zero is found.
> So I could try to see where the problem is.
> 
> Do you know which grid, tiling and parameter file "data" 
> cause this problem ? (I guess you are not using useAreaViscLength=T ?)
> 
> Thanks,
> Jean-Michel
> 
> 
> On Thu, Feb 12, 2009 at 06:12:37PM +0100, Martin Losch wrote:
> > Hi Jean-Michel,
> >
> > the problem occurs only on curvilinear grids (that's why  
> > ini_curvilinear_grid), and it happens somewhere in mom_common/ 
> > mom_calc_visc.F. Basically, L2rdt (and other similar terms) are zero at 
> > some points in the overlaps, I think the corners, so i,j=-2, or so and 
> > then, when there is a division by L2rdt, then the sxf90 compiler  
> > complains/code crashes. The problem goes away with my fix (and we talked 
> > about this some time ago, but obviously since then nothing has changed in 
> > terms of exchanges) and the actual value of the initialization does not 
> > have an impact on the solution at all.
> >
> > You should be able to reproduce this with any cubed sphere grid  
> > (although I only get crashes with sxf90).
> >
> > Martin
> >
> > On Feb 12, 2009, at 6:02 PM, Jean-Michel Campin wrote:
> >
> >> Hi Martin,
> >>
> >> I am little bit confused:
> >> - we do have the proper exchange for dxV & dyU (In fact, I think we
> >>  now have the full familly of exch S/R), may be not the adjoint  
> >> version.
> >> - If there is a division by zero somewhere in the code, I would prefer
> >>  to fix it (for all platforms, not only for NEC_SX) rather than
> >>  leave with it.
> >> Can you point where the problem was ?
> >> Thanks,
> >> Jean-Michel
> >>
> >> On Thu, Feb 12, 2009 at 02:51:56AM -0500, Martin Losch wrote:
> >>> Update of /u/gcmpack/MITgcm/model/src
> >>> In directory forge:/tmp/cvs-serv13873/model/src
> >>>
> >>> Modified Files:
> >>> 	ini_curvilinear_grid.F
> >>> Log Message:
> >>> check my hack for SX8 compiler, because I keep stumbling over it.
> >>> (forgive me, Jean-Michel):
> >>> terrible hack to make sure that recip_dxV and recip_dyU are never  
> >>> zero,
> >>> until we have a proper exchange for them. Most compilers do not seem
> >>> to mind divisions by zero in the overlaps, as long as the results are
> >>> not used anywhere, but sxf90 does.
> >>>
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