[MITgcm-devel] [MITgcm-cvs] MITgcm/doc CVS Commit

[Martin Losch]

The point of the restricted additive Schwarz method is, that your don’t limit the calculation to the tile interior, but extend into the overlaps: seaice_lsr needs two points of overlap, so if you have OLx=4 you can still compute a solution 2 points into this overlap. Afterwards you combine the tiles without the overlap (that’s the “restricted” part). I think it should be immediately clear why this would be a better approximation to the global problem than not using the overlaps in the iterative procedure. My implementation works for non-cs grids without the resetting BU,BV and on cs-grids the problem appears only in the corners of the overlaps which not really used in the computation; at least, without the -devel option, the wrong values in the overlapp corners don’t seem to affect the solution. But I agree, it’s strange … I also need to investigate this a little more, …

Martin

On Dec 10, 2014, at 8:20 PM, Jean-Michel Campin <jmc at ocean.mit.edu> wrote:

> Hi Martin,
> 
> I would leave this routine (fill_cs_corner_rl.F) there for now.
> The thing that is not very clear to me (because I did not have time
> to look at the details of this Schwarz method implementation) is
> why setting BU,BV to one in these overlap region is going to be more 
> accurate than limiting the calculation to just the tile interior.
> 
> Cheers,
> Jean-Michel
> 
> On Wed, Dec 10, 2014 at 06:06:37PM +0100, Martin Losch wrote:
>> Hi Jean-Michel,
>> 
>> I think I fixed this problem by resetting bu/bv=1 if they are zero (but I do this only for cubedSphere and SEAICE_OLx/y>0). The new fill_cs_corner_rl routine is no longer necessary. Should we still keep it?
>> 
>> Martin
>> 
>> On Dec 10, 2014, at 4:41 PM, Martin Losch <Martin.Losch at awi.de> wrote:
>> 
>>> Hi Jean-Michel,
>>> 
>>> thanks for noticing, the reason is the same as before: BU(34,18,2,1) is zero exactly. This should not happen (ever) (see seaice_lsr.F l1259, for seaicemaskU = 0., there should be ONE=1D0 remaining). The quick fix is to reset any BU and BV that are 0 to 1. but then the program stops (within gdb, testreport passes) in seaice_solve4temp because tsurfloc(3,1) = 0 for bi=bj=1, very strange.
>>> 
>>> Should I apply the quick fix for now?
>>> 
>>> Martin
>>> 
>>> On Dec 10, 2014, at 3:31 PM, Jean-Michel Campin <jmc at ocean.mit.edu> wrote:
>>> 
>>>> Hi Martin,
>>>> 
>>>> Regarding the gfortran -devel fail:
>>>> there is a "Floating point exception" error, coming from S/R
>>>> seaice_lsr_tridiagu (in seaice_lsr.F):
>>>>> Backtrace for this error:
>>>>> #0  0x2B893F5E8407
>>>>> #1  0x2B893F5E8A0E
>>>>> #2  0x3C1C83568F
>>>>> #3  0x9735E8 in seaice_lsr_tridiagu_ at seaice_lsr.f:14903 (discriminator 16)
>>>>> #4  0x9A333D in seaice_lsr_ at seaice_lsr.f:4236
>>>>> #5  0x924475 in seaice_dynsolver_ at seaice_dynsolver.f:4354
>>>>> #6  0x9AC0F5 in seaice_model_ at seaice_model.f:4545
>>>>> #7  0xBF45C4 in do_oceanic_phys_ at do_oceanic_phys.f:3370 (discriminator 3)
>>>>> #8  0xC1DADF in forward_step_ at forward_step.f:2467
>>>>> #9  0xCD1569 in main_do_loop_ at main_do_loop.f:2145
>>>>> #10  0xD3DB28 in the_main_loop_ at the_main_loop.f:2163
>>>>> #11  0xD3DCFB in the_model_main_ at the_model_main.f:2426
>>>>> #12  0xAF887E in MAIN__ at main.f:3772
>>>>> Floating exception (core dumped)
>>>> 
>>>> Since it's failing on baudelaire with gfortran and -devel,
>>>> you should be able to reproduce the error.
>>>> 
>>>> Cheers,
>>>> Jean-Michel
>>>> 
>>>> On Wed, Dec 10, 2014 at 09:06:44AM -0500, Jean-Michel Campin wrote:
>>>>> Hi Martin,
>>>>> 
>>>>> global_ocean.cs32x15.seaice experiment is failing in few cases
>>>>> (pgi compiler, other compiler using -devel, also on uv100).
>>>>> Presently looking at this.
>>>>> 
>>>>> Cheers,
>>>>> Jean-Michel
>>>>> 
>>>>> On Tue, Dec 09, 2014 at 09:17:23AM -0500, Martin Losch wrote:
>>>>>> Update of /u/gcmpack/MITgcm/doc
>>>>>> In directory forge:/tmp/cvs-serv30680/doc
>>>>>> 
>>>>>> Modified Files:
>>>>>> 	tag-index 
>>>>>> Log Message:
>>>>>> document changes in verification/global_ocean.cs32x15/input.seaice
>>>>>> - add test for strong implicit coupling and restricted addtive Schwarz
>>>>>>  methods for LSR
>>>>>> - update results/output.seaice.txt
>>>>>> 
>>>>>> 
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