[MITgcm-support] Equatorial Channel from -70 degree to +70 degree

[Jean-Michel Campin]

Hi Yuan,

Currently, the zonal filter only works with no tile
decomposition (i.e. single tile) in the X direction.
If you want to use it in your set-up, you will need
to find the 8 tiles in the Y direction (e.g.:
increasing Ny to 96 and setting nPy=8, nSy=12, 
keeping nSx=256)

Jean-Michel

> Hi, Dimitris and Martin,
> 
> I just figured out that the problem is actually caused by zonal filter. 
> I thought I shoud apply zonal filter if the latitude is greater than 45 
> degree. Once the zonal filter was turned off, the code just ran 
> smoothly. I feel a little uncomfortable that I have to turn off zonal 
> filter. This might cause problems when the channel is close to polar 
> region, say, a channel from -80 degree to +80 degree. However I think I 
> can just reduce time step if the zonal filter is turned off.
> 
> Yuan
> 
> Martin Losch wrote:
> 
> >Yuan,
> >
> >the results from
> >nPx=8, sNx=32, sNy=93 should be exactly the same (except for round- 
> >off error) as those from
> >nPx=4, sNx=64, sNy=93,
> >nPx=2, sNx=128, sNy=93, and
> >nPx=1, sNx=256, sNy=93, regardless of time step.
> >When you have NaN's in one case and no NaN's in another, then  
> >something else is wrong. What about your nSx/nSy? both should be 1 in  
> >all of these examples so that  sNx*nSx*nPx = 256, and sNy*nSy*nPy =  
> >93 for all cases.
> >
> >Martin
> >
> >On 4 Oct 2006, at 08:29, Yuan Lian wrote:
> >
> >>Hi, Dimitris,
> >>
> >>Thanks. I tried the configuration nPx=8, sNx=32, sNy=93 but the  
> >>simulation gave NAN values. I had to reduce the number of grids in  
> >>latitude. The configuration nPx=4, sNx=64, sNy=63 worked just fine.  
> >>I will try nPx=4, sNx=64, sNy=93 and see how it works. I might try  
> >>to use very short time step as well.
> >>
> >>cheers,
> >>Yuan
> >>
> >>Dimitris Menemenlis wrote:
> >>
> >>>Hi Yuan,
> >>>
> >>>>I noticed that, in order to run the simulation, the number of  grid 
> >>>>points in
> >>>>X direction has to be greater than the number of grids in Y  
> >>>>direction in a
> >>>>single tile.
> >>>
> >>>
> >>>
> >>>There is no such restriction as far as possible model  
> >>>configurations are concerned.
> >>>
> >>>>The number of grids is 256x93
> >>>>So the question is: how to configure the "SIZE.h" to run the  
> >>>>simulation with
> >>>>4 or 8 processors?
> >>>
> >>>
> >>>
> >>>Since 93 is not divisible by 2, and assuming you are using MPI,   
> >>>you can have
> >>> nPx=4, sNx=64, sNy=93 and
> >>> nPx=8, sNx=32, sNy=93.
> >>>
> >>>Cheers, Dimitris
> >>>
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