C $Header: /u/gcmpack/MITgcm/pkg/seaice/seaice_jfnk.F,v 1.30 2016/01/28 12:54:12 mlosch Exp $ C $Name: $ #include "SEAICE_OPTIONS.h" #ifdef ALLOW_AUTODIFF # include "AUTODIFF_OPTIONS.h" #endif C-- File seaice_jfnk.F: seaice jfnk dynamical solver S/R: C-- Contents C-- o SEAICE_JFNK C-- o SEAICE_JFNK_UPDATE CBOP C !ROUTINE: SEAICE_JFNK C !INTERFACE: SUBROUTINE SEAICE_JFNK( myTime, myIter, myThid ) C !DESCRIPTION: \bv C *==========================================================* C | SUBROUTINE SEAICE_JFNK C | o Ice dynamics using a Jacobian-free Newton-Krylov solver C | following J.-F. Lemieux et al. Improving the numerical C | convergence of viscous-plastic sea ice models with the C | Jacobian-free Newton-Krylov method. J. Comp. Phys. 229, C | 2840-2852 (2010). C | o The logic follows JFs code. C *==========================================================* C | written by Martin Losch, Oct 2012 C *==========================================================* C \ev C !USES: IMPLICIT NONE C === Global variables === #include "SIZE.h" #include "EEPARAMS.h" #include "PARAMS.h" #include "DYNVARS.h" #include "GRID.h" #include "SEAICE_SIZE.h" #include "SEAICE_PARAMS.h" #include "SEAICE.h" #ifdef ALLOW_AUTODIFF_TAMC # include "tamc.h" #endif C !INPUT/OUTPUT PARAMETERS: C === Routine arguments === C myTime :: Simulation time C myIter :: Simulation timestep number C myThid :: my Thread Id. number _RL myTime INTEGER myIter INTEGER myThid #ifdef SEAICE_ALLOW_JFNK C !FUNCTIONS: LOGICAL DIFFERENT_MULTIPLE EXTERNAL DIFFERENT_MULTIPLE C !LOCAL VARIABLES: C === Local variables === C i,j,bi,bj :: loop indices INTEGER i,j,bi,bj C loop indices INTEGER newtonIter INTEGER krylovIter, krylovFails INTEGER totalKrylovItersLoc, totalNewtonItersLoc C FGMRES parameters C im :: size of Krylov space C ifgmres :: interation counter INTEGER im PARAMETER ( im = 50 ) INTEGER ifgmres C FGMRES flag that determines amount of output messages of fgmres INTEGER iOutFGMRES C FGMRES flag that indicates what fgmres wants us to do next INTEGER iCode _RL JFNKresidual _RL JFNKresidualKm1 C parameters to compute convergence criterion _RL JFNKgamma_lin _RL FGMRESeps _RL JFNKtol C backward differences extrapolation factors _RL bdfFac, bdfAlpha C _RL recip_deltaT LOGICAL JFNKconverged, krylovConverged LOGICAL writeNow CHARACTER*(MAX_LEN_MBUF) msgBuf C u/vIceRes :: residual of sea-ice momentum equations _RL uIceRes(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL vIceRes(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) C extra time level required for backward difference time stepping _RL duIcNm1(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL dvIcNm1(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) C du/vIce :: ice velocity increment to be added to u/vIce _RL duIce (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL dvIce (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) C precomputed (= constant per Newton iteration) versions of C zeta, eta, and DWATN, press _RL zetaPre (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL zetaZPre(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL etaPre (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL etaZPre (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL dwatPre (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) C work arrays _RL rhs(nVec,nSx,nSy), sol(nVec,nSx,nSy) _RL vv(nVec,im+1,nSx,nSy), w(nVec,im,nSx,nSy) _RL wk1(nVec,nSx,nSy), wk2(nVec,nSx,nSy) CEOP C Initialise newtonIter = 0 krylovFails = 0 totalKrylovItersLoc = 0 JFNKconverged = .FALSE. JFNKtol = 0. _d 0 JFNKresidual = 0. _d 0 JFNKresidualKm1 = 0. _d 0 FGMRESeps = 0. _d 0 recip_deltaT = 1. _d 0 / SEAICE_deltaTdyn iOutFGMRES=0 C with iOutFgmres=1, seaice_fgmres prints the residual at each iteration IF ( debugLevel.GE.debLevC .AND. & DIFFERENT_MULTIPLE( SEAICE_monFreq, myTime, deltaTClock ) ) & iOutFGMRES=1 C backward difference extrapolation factors bdfFac = 0. _d 0 IF ( SEAICEuseBDF2 ) THEN IF ( myIter.EQ.nIter0 .AND. SEAICEmomStartBDF.EQ.0 ) THEN bdfFac = 0. _d 0 ELSE bdfFac = 0.5 _d 0 ENDIF ENDIF bdfAlpha = 1. _d 0 + bdfFac DO bj=myByLo(myThid),myByHi(myThid) DO bi=myBxLo(myThid),myBxHi(myThid) DO J=1-OLy,sNy+OLy DO I=1-OLx,sNx+OLx uIceRes(I,J,bi,bj) = 0. _d 0 vIceRes(I,J,bi,bj) = 0. _d 0 duIce (I,J,bi,bj) = 0. _d 0 dvIce (I,J,bi,bj) = 0. _d 0 ENDDO ENDDO C cycle ice velocities DO J=1-OLy,sNy+OLy DO I=1-OLx,sNx+OLx duIcNm1(I,J,bi,bj) = uIce(I,J,bi,bj) * bdfAlpha & + ( uIce(I,J,bi,bj) - uIceNm1(I,J,bi,bj) ) * bdfFac dvIcNm1(I,J,bi,bj) = vIce(I,J,bi,bj) * bdfAlpha & + ( vIce(I,J,bi,bj) - vIceNm1(I,J,bi,bj) ) * bdfFac uIceNm1(I,J,bi,bj) = uIce(I,J,bi,bj) vIceNm1(I,J,bi,bj) = vIce(I,J,bi,bj) ENDDO ENDDO C As long as IMEX is not properly implemented leave this commented out CML IF ( .NOT.SEAICEuseIMEX ) THEN C Compute things that do no change during the Newton iteration: C sea-surface tilt and wind stress: C FORCEX/Y0 - mass*(1.5*u/vIceNm1+0.5*(u/vIceNm1-u/vIceNm2))/deltaT DO J=1-OLy,sNy+OLy DO I=1-OLx,sNx+OLx FORCEX(I,J,bi,bj) = FORCEX0(I,J,bi,bj) & + seaiceMassU(I,J,bi,bj)*duIcNm1(I,J,bi,bj)*recip_deltaT FORCEY(I,J,bi,bj) = FORCEY0(I,J,bi,bj) & + seaiceMassV(I,J,bi,bj)*dvIcNm1(I,J,bi,bj)*recip_deltaT ENDDO ENDDO CML ENDIF ENDDO ENDDO C Start nonlinear Newton iteration: outer loop iteration DO WHILE ( newtonIter.LT.SEAICEnonLinIterMax .AND. & .NOT.JFNKconverged ) newtonIter = newtonIter + 1 C Compute initial residual F(u), (includes computation of global C variables DWATN, zeta, and eta) IF ( newtonIter .EQ. 1 ) CALL SEAICE_JFNK_UPDATE( I duIce, dvIce, U uIce, vIce, JFNKresidual, O uIceRes, vIceRes, I newtonIter, myTime, myIter, myThid ) C local copies of precomputed coefficients that are to stay C constant for the preconditioner DO bj=myByLo(myThid),myByHi(myThid) DO bi=myBxLo(myThid),myBxHi(myThid) DO j=1-OLy,sNy+OLy DO i=1-OLx,sNx+OLx zetaPre(I,J,bi,bj) = zeta(I,J,bi,bj) zetaZPre(I,J,bi,bj)= zetaZ(I,J,bi,bj) etaPre(I,J,bi,bj) = eta(I,J,bi,bj) etaZPre(I,J,bi,bj) = etaZ(I,J,bi,bj) dwatPre(I,J,bi,bj) = DWATN(I,J,bi,bj) ENDDO ENDDO ENDDO ENDDO C compute convergence criterion for linear preconditioned FGMRES JFNKgamma_lin = JFNKgamma_lin_max IF ( newtonIter.GT.1.AND.newtonIter.LE.SEAICE_JFNK_tolIter & .AND.JFNKresidual.LT.JFNKres_t ) THEN C Eisenstat and Walker (1996), eq.(2.6) JFNKgamma_lin = SEAICE_JFNKphi & *( JFNKresidual/JFNKresidualKm1 )**SEAICE_JFNKalpha JFNKgamma_lin = min(JFNKgamma_lin_max, JFNKgamma_lin) JFNKgamma_lin = max(JFNKgamma_lin_min, JFNKgamma_lin) ENDIF C save the residual for the next iteration JFNKresidualKm1 = JFNKresidual C The Krylov iteration using FGMRES, the preconditioner is LSOR C for now. The code is adapted from SEAICE_LSR, but heavily stripped C down. C krylovIter is mapped into "its" in seaice_fgmres and is incremented C in that routine krylovIter = 0 iCode = 0 JFNKconverged = JFNKresidual.LT.JFNKtol C do Krylov loop only if convergence is not reached IF ( .NOT.JFNKconverged ) THEN C start Krylov iteration (FGMRES) krylovConverged = .FALSE. FGMRESeps = JFNKgamma_lin * JFNKresidual C map first guess sol; it is zero because the solution is a correction CALL SEAICE_MAP2VEC(nVec,duIce,dvIce,sol,.TRUE.,myThid) C map rhs and change its sign because we are solving J*u = -F CALL SEAICE_MAP2VEC(nVec,uIceRes,vIceRes,rhs,.TRUE.,myThid) DO bj=myByLo(myThid),myByHi(myThid) DO bi=myBxLo(myThid),myBxHi(myThid) DO j=1,nVec rhs(j,bi,bj) = - rhs(j,bi,bj) ENDDO ENDDO ENDDO DO WHILE ( .NOT.krylovConverged ) C solution vector sol = du/vIce C residual vector (rhs) Fu = u/vIceRes C output work vectors wk1, -> input work vector wk2 C map preconditioner results or Jacobian times vector, C stored in du/vIce to wk2, for iCode=0, wk2 is set to zero, C because du/vIce = 0 CALL SEAICE_MAP2VEC(nVec,duIce,dvIce,wk2,.TRUE.,myThid) C CALL SEAICE_FGMRES (nVec,im,rhs,sol,ifgmres,krylovIter, U vv,w,wk1,wk2, I FGMRESeps,SEAICElinearIterMax,iOutFGMRES, U iCode, I myThid) C IF ( iCode .EQ. 0 ) THEN C map sol(ution) vector to du/vIce CALL SEAICE_MAP2VEC(nVec,duIce,dvIce,sol,.FALSE.,myThid) ELSE C map work vector to du/vIce to either compute a preconditioner C solution (wk1=rhs) or a Jacobian times wk1 CALL SEAICE_MAP2VEC(nVec,duIce,dvIce,wk1,.FALSE.,myThid) ENDIF C Fill overlaps in updated fields CALL EXCH_UV_XY_RL( duIce, dvIce,.TRUE.,myThid) C FGMRES returns iCode either asking for an new preconditioned vector C or product of matrix (Jacobian) times vector. For iCode = 0, terminate C iteration IF (iCode.EQ.1) THEN C Call preconditioner IF ( SEAICEpreconLinIter .GT. 0 ) & CALL SEAICE_PRECONDITIONER( U duIce, dvIce, I zetaPre, etaPre, etaZpre, zetaZpre, dwatPre, I newtonIter, krylovIter, myTime, myIter, myThid ) ELSEIF (iCode.GE.2) THEN C Compute Jacobian times vector CALL SEAICE_JACVEC( I uIce, vIce, uIceRes, vIceRes, U duIce, dvIce, I newtonIter, krylovIter, myTime, myIter, myThid ) ENDIF krylovConverged = iCode.EQ.0 C End of Krylov iterate ENDDO totalKrylovItersLoc = totalKrylovItersLoc + krylovIter C some output diagnostics IF ( debugLevel.GE.debLevA ) THEN _BEGIN_MASTER( myThid ) totalNewtonItersLoc = & SEAICEnonLinIterMax*(myIter-nIter0)+newtonIter WRITE(msgBuf,'(2A,2(1XI6),2E12.5)') & ' S/R SEAICE_JFNK: Newton iterate / total, ', & 'JFNKgamma_lin, initial norm = ', & newtonIter, totalNewtonItersLoc, & JFNKgamma_lin,JFNKresidual CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(3(A,I6))') & ' S/R SEAICE_JFNK: Newton iterate / total = ',newtonIter, & ' / ', totalNewtonItersLoc, & ', Nb. of FGMRES iterations = ', krylovIter CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) _END_MASTER( myThid ) ENDIF IF ( krylovIter.EQ.SEAICElinearIterMax ) THEN krylovFails = krylovFails + 1 ENDIF C Set the stopping criterion for the Newton iteration and the C criterion for the transition from accurate to approximate FGMRES IF ( newtonIter .EQ. 1 ) THEN JFNKtol=SEAICEnonLinTol*JFNKresidual IF ( JFNKres_tFac .NE. UNSET_RL ) & JFNKres_t = JFNKresidual * JFNKres_tFac ENDIF C Update linear solution vector and return to Newton iteration C Do a linesearch if necessary, and compute a new residual. C Note that it should be possible to do the following operations C at the beginning of the Newton iteration, thereby saving us from C the extra call of seaice_jfnk_update, but unfortunately that C changes the results, so we leave the stuff here for now. CALL SEAICE_JFNK_UPDATE( I duIce, dvIce, U uIce, vIce, JFNKresidual, O uIceRes, vIceRes, I newtonIter, myTime, myIter, myThid ) C reset du/vIce here instead of setting sol = 0 in seaice_fgmres_driver DO bj=myByLo(myThid),myByHi(myThid) DO bi=myBxLo(myThid),myBxHi(myThid) DO J=1-OLy,sNy+OLy DO I=1-OLx,sNx+OLx duIce(I,J,bi,bj)= 0. _d 0 dvIce(I,J,bi,bj)= 0. _d 0 ENDDO ENDDO ENDDO ENDDO ENDIF C end of Newton iterate ENDDO C-- Output diagnostics IF ( SEAICE_monFreq .GT. 0. _d 0 ) THEN C Count iterations totalJFNKtimeSteps = totalJFNKtimeSteps + 1 totalNewtonIters = totalNewtonIters + newtonIter totalKrylovIters = totalKrylovIters + totalKrylovItersLoc C Record failure totalKrylovFails = totalKrylovFails + krylovFails IF ( newtonIter .EQ. SEAICEnonLinIterMax ) THEN totalNewtonFails = totalNewtonFails + 1 ENDIF ENDIF C Decide whether it is time to dump and reset the counter writeNow = DIFFERENT_MULTIPLE(SEAICE_monFreq, & myTime+deltaTClock, deltaTClock) #ifdef ALLOW_CAL IF ( useCAL ) THEN CALL CAL_TIME2DUMP( I zeroRL, SEAICE_monFreq, deltaTClock, U writeNow, I myTime+deltaTclock, myIter+1, myThid ) ENDIF #endif IF ( writeNow ) THEN _BEGIN_MASTER( myThid ) WRITE(msgBuf,'(A)') &' // =======================================================' CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A)') ' // Begin JFNK statistics' CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A)') &' // =======================================================' CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A,I10)') & ' %JFNK_MON: time step = ', myIter+1 CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A,I10)') & ' %JFNK_MON: Nb. of time steps = ', totalJFNKtimeSteps CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A,I10)') & ' %JFNK_MON: Nb. of Newton steps = ', totalNewtonIters CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A,I10)') & ' %JFNK_MON: Nb. of Krylov steps = ', totalKrylovIters CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A,I10)') & ' %JFNK_MON: Nb. of Newton failures = ', totalNewtonFails CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A,I10)') & ' %JFNK_MON: Nb. of Krylov failures = ', totalKrylovFails CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A)') &' // =======================================================' CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A)') ' // End JFNK statistics' CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) WRITE(msgBuf,'(A)') &' // =======================================================' CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) _END_MASTER( myThid ) C reset and start again totalJFNKtimeSteps = 0 totalNewtonIters = 0 totalKrylovIters = 0 totalKrylovFails = 0 totalNewtonFails = 0 ENDIF C Print more debugging information IF ( debugLevel.GE.debLevA ) THEN IF ( newtonIter .EQ. SEAICEnonLinIterMax ) THEN _BEGIN_MASTER( myThid ) WRITE(msgBuf,'(A,I10)') & ' S/R SEAICE_JFNK: JFNK did not converge in timestep ', & myIter+1 CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) _END_MASTER( myThid ) ENDIF IF ( krylovFails .GT. 0 ) THEN _BEGIN_MASTER( myThid ) WRITE(msgBuf,'(A,I4,A,I10)') & ' S/R SEAICE_JFNK: FGMRES did not converge ', & krylovFails, ' times in timestep ', myIter+1 CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) _END_MASTER( myThid ) ENDIF _BEGIN_MASTER( myThid ) WRITE(msgBuf,'(A,I6,A,I10)') & ' S/R SEAICE_JFNK: Total number FGMRES iterations = ', & totalKrylovItersLoc, ' in timestep ', myIter+1 CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) _END_MASTER( myThid ) ENDIF RETURN END C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----| CBOP C !ROUTINE: SEAICE_JFNK_UPDATE C !INTERFACE: SUBROUTINE SEAICE_JFNK_UPDATE( I duIce, dvIce, U uIce, vIce, JFNKresidual, O uIceRes, vIceRes, I newtonIter, myTime, myIter, myThid ) C !DESCRIPTION: \bv C *==========================================================* C | SUBROUTINE SEAICE_JFNK_UPDATE C | o Update velocities with incremental solutions of FGMRES C | o compute residual of updated solutions and do C | o linesearch: C | reduce update until residual is smaller than previous C | one (input) C *==========================================================* C | written by Martin Losch, Jan 2013 C *==========================================================* C \ev C !USES: IMPLICIT NONE C === Global variables === #include "SIZE.h" #include "EEPARAMS.h" #include "PARAMS.h" #include "SEAICE_SIZE.h" #include "SEAICE_PARAMS.h" C !INPUT/OUTPUT PARAMETERS: C === Routine arguments === C myTime :: Simulation time C myIter :: Simulation timestep number C myThid :: my Thread Id. number C newtonIter :: current iterate of Newton iteration _RL myTime INTEGER myIter INTEGER myThid INTEGER newtonIter C JFNKresidual :: Residual at the beginning of the FGMRES iteration, C changes with newtonIter (updated) _RL JFNKresidual C du/vIce :: ice velocity increment to be added to u/vIce (input) _RL duIce (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL dvIce (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) C u/vIce :: ice velocity increment to be added to u/vIce (updated) _RL uIce (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL vIce (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) C u/vIceRes :: residual of sea-ice momentum equations (output) _RL uIceRes(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL vIceRes(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) C !LOCAL VARIABLES: C === Local variables === C i,j,bi,bj :: loop indices INTEGER i,j,bi,bj INTEGER l _RL resLoc, facLS LOGICAL doLineSearch C nVec :: size of the input vector(s) C resTmp :: vector version of the residuals INTEGER nVec PARAMETER ( nVec = 2*sNx*sNy ) _RL resTmp (nVec,1,nSx,nSy) CHARACTER*(MAX_LEN_MBUF) msgBuf CEOP C Initialise some local variables l = 0 resLoc = JFNKresidual facLS = 1. _d 0 doLineSearch = .TRUE. DO WHILE ( doLineSearch ) C Create update DO bj=myByLo(myThid),myByHi(myThid) DO bi=myBxLo(myThid),myBxHi(myThid) DO J=1-OLy,sNy+OLy DO I=1-OLx,sNx+OLx uIce(I,J,bi,bj) = uIce(I,J,bi,bj)+facLS*duIce(I,J,bi,bj) vIce(I,J,bi,bj) = vIce(I,J,bi,bj)+facLS*dvIce(I,J,bi,bj) ENDDO ENDDO ENDDO ENDDO C Compute current residual F(u), (includes re-computation of global C variables DWATN, zeta, and eta, i.e. they are different after this) CALL SEAICE_CALC_RESIDUAL( I uIce, vIce, O uIceRes, vIceRes, I newtonIter, 0, myTime, myIter, myThid ) C Important: Compute the norm of the residual using the same scalar C product that SEAICE_FGMRES does CALL SEAICE_MAP2VEC(nVec,uIceRes,vIceRes,resTmp,.TRUE.,myThid) CALL SEAICE_SCALPROD(nVec,1,1,1,resTmp,resTmp,resLoc,myThid) resLoc = SQRT(resLoc) C Determine, if we need more iterations doLineSearch = resLoc .GE. JFNKresidual C Limit the maximum number of iterations arbitrarily to four doLineSearch = doLineSearch .AND. l .LT. 4 C For the first iteration du/vIce = 0 and there will be no C improvement of the residual possible, so we do only the first C iteration IF ( newtonIter .EQ. 1 ) doLineSearch = .FALSE. C Only start a linesearch after some Newton iterations IF ( newtonIter .LE. SEAICE_JFNK_lsIter ) doLineSearch = .FALSE. C Increment counter l = l + 1 C some output diagnostics IF ( debugLevel.GE.debLevA .AND. doLineSearch ) THEN _BEGIN_MASTER( myThid ) WRITE(msgBuf,'(2A,2(1XI6),3E12.5)') & ' S/R SEAICE_JFNK_UPDATE: Newton iter, LSiter, ', & 'facLS, JFNKresidual, resLoc = ', & newtonIter, l, facLS, JFNKresidual, resLoc CALL PRINT_MESSAGE( msgBuf, standardMessageUnit, & SQUEEZE_RIGHT, myThid ) _END_MASTER( myThid ) ENDIF C Get ready for the next iteration: after adding du/vIce in the first C iteration, we substract 0.5*du/vIce from u/vIce in the next C iterations, 0.25*du/vIce in the second, etc. facLS = - 0.5 _d 0 * ABS(facLS) ENDDO C This is the new residual JFNKresidual = resLoc #endif /* SEAICE_ALLOW_JFNK */ RETURN END