[MITgcm-support] The way to accelerate the calculation speed or to expand deltaT of MITgcm

[Christopher L. Wolfe]

Hi Matt,

With 72 vertical levels, how do you avoid blowing your vertical cdf condition? I've got only 20 levels (smallest ~10m) and a time step of 500 s and my vertical cdf numbers hover around 0.2. Are you using implicit vertical advection?

Cheers,
Christopher

On Oct 28, 2010, at 11:11 AM, Matthew Mazloff wrote:

> Hi Liang,
> 
> There are several things to try.  First though, did you try any scaling experiments - 48 cpus may actually be too many.  Obviously it depends on your architecture, but due to overlaps usually efficient tile sizes for most machines is about 30 x 30.  I would therefore guess that your setup would run better on ~12 cpus, not 48...
> 
> Other things to try is limiting output by setting  debugLevel=0, in PARM01
> changing way I/O is done by trying
> useSingleCpuIO=.TRUE.,
> again in PARM01
> 
> Also -- I have a setup running with 6km resolution and 72 vertical levels -- very similar to yours -- and I use a timestep of 1200.0 seconds.  Perhaps increasing your diff and visc will give you a more stable solution -- I use:
>  viscAz =1.E-4,
>  viscAh =1.E2,
>  viscA4 =1.E9,
>  diffKhT=1.E0,
>  diffKzT=1.E-5,
>  diffKhS=1.E0,
>  diffKzS=1.E-5,
>  bottomDragQuadratic=1.E-3,
>  tempAdvScheme=30,
>  saltAdvScheme=30,
> 
> Still -- 30 years is a long run -- it will likely take significant time to run...
> 
> good luck,
> -Matt
> 
> 
> 
> 
> On Oct 28, 2010, at 5:27 AM, 姊佹湅 wrote:
> 
>> Dear Sir:
>>         I'm trying to use the MITgcm to run an experiment.To simulate this experiment
>> successfully it is necessary to set the grid interval to be very small.Now the number of the horizontal grids is 114*104,and the number of the vertical grids is 139.The minimum interval of the horizontal grids is 5 km ,and the minimum interval of the vertical grids is 10m.And now I find that the maximum deltaT in the data file to keep the model steady is 60s. The minimum time that is needed is 30 years,so the minimum number of timesteps (nTimeSteps in the data file)is 16000000.Now I have used 48 cpu to run the model,and it needs 210 days to finish the calculation.The time is too long!! So can you tell me how to  set the model parameters or modify the model code to  accelerate the calculation speed or to expand deltaT.
>> Thank You,
>> With Regards,
>> Liang 
>>     Some of the parameters I set are as follow:
>>     The grids of x and y  are as follow:
>>     nx=104;
>>     ny=114;
>>     dx(1:20)=50;
>>     dx(21:27)=[40:-5:10];
>>     dx(28:67)=5;
>>     dx(68:74)=[10:5:40];
>>     dx(75:nx)=50;
>>     dx=dx*1000;
>>     dy(1:38)=25;
>>     dy(39:42)=[21:-4:9];
>>     dy(43:92)=5;
>>     dy(93:96)=[9:4:21];
>>     dy(97:ny)=25;
>>     dy=dy*1000;
>>     The settings of the data file are as follow:
>>       &PARM01
>>   tRef=139*20.,
>>  sRef=139*35.,
>>  viscAh=0.,
>>  viscAhGrid=0.,
>>  viscC2Leith=0.,
>>  viscA4=0.,
>>  useFullLeith=.TRUE.,
>>  viscC4Leith=2.0,
>>  viscC4Leithd=2.0,
>>  viscAz=1.E-3,
>>  bottomDragLinear=0.E-4,
>>  bottomDragQuadratic=0.003,
>>  no_slip_sides=.TRUE.,
>>  no_slip_bottom=.TRUE.,
>>  diffK4T=0.E4,
>>  diffKhT=0.E-2,
>>  diffKzT=0.E-3,
>>  diffK4S=0.E4,
>>  diffKhS=0.E-2,
>>  diffKzS=0.E-5,
>>  f0=4.97e-5,
>>  beta=2.30e-11,
>>  rhonil=1035.,
>>  rhoConstFresh=1000.,
>>  eosType = 'JMD95Z',
>>  rigidLid=.FALSE.,
>>  implicitFreeSurface=.TRUE.,
>>  hFacMin=0.05,
>>  nonHydrostatic=.TRUE.,
>>  readBinaryPrec=64,
>> #- not safe to use globalFiles in multi-processors runs
>> #globalFiles=.TRUE.,
>>  tempAdvScheme=33,
>>  &
>> # Elliptic solver parameters
>>  &PARM02
>>  cg2dMaxIters=300,
>>  cg2dTargetResidual=1.E-13,
>>  cg3dMaxIters=20,
>>  cg3dTargetResidual=1.E-8,
>>  &
>> # Time stepping parameters
>>  &PARM03
>>  nIter0=0,
>>  nTimeSteps=16000000,
>>  deltaT=60.0,
>>  abEps=0.01,
>>  pChkptFreq=600000.0,
>>  chkptFreq=600000.0,
>>  dumpFreq=6000000.0,
>>  tauThetaClimRelax=100000.0,
>>  monitorFreq=60000.,
>>  &
>> # Gridding parameters
>>  &PARM04
>>  usingCartesianGrid=.TRUE.,
>>  delXfile='dx.bin',
>>  delYfile='dy.bin',
>>  delZ=100,100,100,100,100,100,100,100,100,100,90,80,70,60,50,40,30,20,102*10,20,30,40,50,60,70,80,90,100,100,100,100,100,100,100,100,100,100,100,
>>  &
>> # Input datasets
>>  &PARM05
>>  bathyFile='topog.slope',
>>  hydrogThetaFile='T.init',
>>  surfQfile='Qnet.forcing',
>>  thetaClimFile='SST.bin',
>>  diffKrFile='diffK.bin',
>>  &
>> 
>>  <ATT00001.txt>
> 
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