[MITgcm-support] RBCS computer time

[Olivier Arzel]

Hello all,

I'm using the RBCS (3D restoring) package and have noticed that this 
considerably slows down the model integration. Compared to a run that 
does not use this option the computer time increases typically by a 
factor 10 with exactly the same configuration and model parameters and 
with 64 procs on a SGI machine. Where does come from this behaviour and 
what can I do to overcome this issue ? I use a cyclic forcing with 12 
monthly average velocity data (with readbinaryprec=64) and apply strong 
restoring with a short timescale of 8100s (the tracer time step in my 
model configuration). Below are my data and data.rbcs files

data:

# ====================
# | Model parameters |
# ====================
#
# Continuous equation parameters
  &PARM01
  tRef = 44*4.,
  sRef = 44*35.,
  viscAr=1.E-4,
  viscAh=5.0E4,
  diffKhT=0.,
  diffKrT=0.,
  diffKhS=0.,
  diffKrS=0.,
  diffKrBL79surf=0.5E-4,
  diffKrBL79deep=1.3E-4,
  diffKrBL79scl= 200.,
  diffKrBL79Ho=-2500.,
  bottomDragLinear=0.,
  bottomDragQuadratic=2.E-3,
  tempAdvScheme=2,
  saltAdvScheme=2,
  rhonil=1035.,
  rhoConstFresh=1000.,
  eosType = 'JMD95Z',
  ivdc_kappa=100.,
  implicitDiffusion=.TRUE.,
  allowFreezing=.FALSE.,
  exactConserv=.TRUE.,
  linFSConserveTr=.TRUE.,
  useRealFreshWaterFlux=.FALSE.,
  useCDscheme=.FALSE.,
  tempAdvection=.TRUE.,
  saltAdvection=.TRUE.,
  momViscosity = .FALSE.,
  momAdvection = .FALSE.,
  metricTerms=.FALSE.,
  useCoriolis=.FALSE.,
  momForcing = .TRUE.,
  momPressureForcing = .FALSE.,
  hFacMin=.05,
  hFacMindr=50.,
  readBinaryPrec=64,
  debuglevel=-1,
  &

# Elliptic solver parameters
  &PARM02
  cg2dMaxIters=500,
  cg2dTargetResidual=1.E-13,
  &

# Time stepping parameters
  &PARM03
  nIter0=  27648000,
  startTime =          0.,
  endTime   = 9331200000.,
  deltaTmom = 300.,
  deltaT = 8100.,
  deltaTfreesurf= 10800.,
  abEps = 0.1,
  pChkptFreq= 311040000.,
  monitorFreq=31104000.,
  periodicExternalForcing=.TRUE.,
  externForcingPeriod=2592000.,
  externForcingCycle=31104000.,
  &

# Gridding parameters
  &PARM04
  usingSphericalPolarGrid=.TRUE.,
  delR= 10., 10., 10., 10., 10., 25., 25., 25., 25., 25.,
        25., 50., 50., 50., 50., 100., 100., 100., 100., 100.,
        100., 100., 100., 100., 100., 100., 250., 250., 250., 250.,
        250., 250., 250., 250., 250., 250., 250., 250., 250., 250.,
        250., 250.,250., 250.,
  ygOrigin=-80.,
  dySpacing=1.,
  dxSpacing=1.,
  &

# Input datasets
  &PARM05
  bathyFile=      'bathymetry.bin',
  hydrogThetaFile=,
  hydrogSaltFile= ,
  zonalWindFile=  ,
  meridWindFile=  ,
  thetaClimFile=  ,
  saltClimFile=   ,
  surfQFile=      'shf.bin',
  the_run_name=   'rbcs',
  EmPmRFile=      'emp.bin',
  &

data.rbcs:

# RBCS package parameters:
  &RBCS_PARM01
     tauRelaxU=8100.,
     tauRelaxV=8100.,
     tauRelaxT=,
     tauRelaxS=,
     relaxMaskUFile='masku_rbcs.bin',
     relaxMaskVFile='maskv_rbcs.bin',
     relaxMaskFile(1)=,
     relaxMaskFile(2)=,
     relaxUFile='uvel_rbcs.bin',
     relaxVFile='vvel_rbcs.bin',
     relaxSFile=,
     relaxSFile=,
     useRBCuVel=.TRUE.,
     useRBCvVel=.TRUE.,
     useRBCtemp=.FALSE.,
     useRBCsalt=.FALSE.,
#   rbcsIniter=100,
     rbcsForcingPeriod=2592000.,
     rbcsForcingCycle=31104000.,
  &

Thanks a lot,

Olivier