SNES Problem
Barry Smith
bsmith at mcs.anl.gov
Wed Mar 15 07:14:25 CST 2006
On Wed, 15 Mar 2006, Nils Erik Svangård wrote:
>>
>> Just get a copy of rk.c and link it in with your code; you don't have
>> to muck with the actual file that goes into the PETSc library.
>>
>
> Ok.
>
>>> In the back-euler implementation, I think I just have to add one line
>>> to get the stability checking of the timestep working.
>>
>> If it is one line for backward Euler, why isn't one line for RK?
>> You can simply call the code in fortran that computes the time-step,
>> can't you then use MPI_Allreduce to get the min over all processors.
>
> It is one line to add in the SNES implementation because there I set
> timestep for each iteration. The RK is used via TS which manage the
> timestep, and I am not sure how to manage the timestep myself in when
> using TS,
I see. Yes, it is a little harder since you have to edit rk.c
but it is still pretty easy.
>
>>
>> Here is the issue: the ONLY reason to use an implicit method is to
>> increase the timestep which you cannot do with the explicit code due
>> to stability constraints. But if you use the same time-step with the
>> implicit code as with the explicit code you gain nothing over using
>> the explicit code (in fact you do worse because the implicit code
>> is more expensive per timestep).
>
> So using the old timestep control function might make the code to work
> but probably will reach the solution much slower. So if this work, I
> probably have to rewrite the stability check to fit the implicit
> timestepping?
Yes.
Barry
>
> /nisse
>
>>
>>
>> Barry
>>
>>>
>>> /nisse
>>>> Barry
>>>>
>>>>
>>>>
>>>> On Tue, 14 Mar 2006, Nils Erik Svangård wrote:
>>>>
>>>>>>> Yes, there is a difference between the old 3-stage RK-solver and the
>>>>>>> SNESsolver using RK. In the old a timestep was calculatade for each
>>>>>> ^^^^^^^^^^^^^^^
>>>>>> Are you using PETSc's explicit RK? If so that does not use SNES.
>>>>>>
>>>>>
>>>>> Sorry, I meant TS.
>>>>>
>>>>>>> cell based on a stability criteria and if chosen it could run in
>>>>>>> time-accurate mode eg. the timestep is the same for each cell, in SNES
>>>>>> ^^^^^^^^^
>>>>>> Do you mean for backward Euler for the explicit RK? Or both?
>>>>>
>>>>> Sorry again, using TS I use the same size of the timestep on every
>>>>> cell (both when trying use back-euler and RK).
>>>>> In my old 3-stage RK I can use both variable timestep and
>>>>> time-accurate timestep.
>>>>> In my seperate back-euler implementation using SNES I use the same
>>>>> timestep on every cell.
>>>>>
>>>>>>
>>>>>>> I use a timestep that is the same for all cells and
>>>>>>> changes only if it returns non-physical answers or the solution diverges.
>>>>>>
>>>>>> I think you need to put the "proper" computation of the time-step
>>>>>> based on the stability criteria that you have in the "old" code.
>>>>>> Unfortunately this is currently hardwired in src/ts/impls/explicit/rk/rk.c
>>>>>> (search for "Computing next stepsize"). I think you need to use the minimum
>>>>>> of the timestep computed here and what is needed for the "stability criteria".
>>>>>>
>>>>> Hmm.. Ok so I could use my back-euler SNES implementation with my old
>>>>> timestep calculation function (using time-accurate timestep)? And it
>>>>> might work better.
>>>>>
>>>>>
>>>>> Thanks
>>>>> /nisse
>>>>>
>>>>>>>
>>>>>>> Another interesting observation is that when using back euler at the
>>>>>>> moment when it bugs out petsc has assigned neigboring cells pressure
>>>>>>> values that differs about 1 ATM, which is a very non physical value,
>>>>>>
>>>>>> Likely some stability problem.
>>>>>>
>>>>>> Barry
>>>>>>
>>>>>>> but I have no clue as to why petsc want such a value in thesolution.
>>>>>>>
>>>>>>> /nisse
>>>>>>>
>>>>>>> On 3/3/06, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>>>>>>>
>>>>>>>> There must be a difference between the two RKs. The initial
>>>>>>>> timestep it uses, or algorithm for changing time step or slight
>>>>>>>> difference in algorithms?
>>>>>>>>
>>>>>>>> Barry
>>>>>>>>
>>>>>>>> On Fri, 3 Mar 2006, Nils Erik Svangård wrote:
>>>>>>>>
>>>>>>>>> A interesting thing is when I change TS_BEULER to TS_RUNGE_KUTTA the
>>>>>>>>> solver exits fast due to the non physical values. My original solver
>>>>>>>>> is a 3-step Runge-Kutta which works flawlessly.
>>>>>>>>>
>>>>>>>>> The error when running RK:
>>>>>>>>>
>>>>>>>>> ./ImplicitG3D on a linux-gnu named sethnx004.vac.com by yy26539 Fri
>>>>>>>>> Mar 3 10:31:27 2006
>>>>>>>>> Libraries linked from /home/yy26539/work/NISSE/petsc-2.3.0/lib/linux-gnu
>>>>>>>>> Configure run at Thu Oct 13 08:23:56 2005
>>>>>>>>> Configure options --with-cc=gcc --with-fc="f77 -N109"
>>>>>>>>> --download-mpich=1 --download-mpich-pm=gforker
>>>>>>>>> --download-f-blas-lapack=1 --with-shared=0
>>>>>>>>> -----------------------------------------------------------------------
>>>>>>>>> [0]PETSC ERROR: Caught signal number 8 FPE: Floating Point
>>>>>>>>> Exception,probably divide by zero
>>>>>>>>> [0]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
>>>>>>>>> [0]PETSC ERROR: likely location of problem given in stack below
>>>>>>>>> [0]PETSC ERROR: --------------- Stack Frames ---------------
>>>>>>>>> [0]PETSC ERROR: Note: The EXACT line numbers in the stack are not available,
>>>>>>>>> [0]PETSC ERROR: INSTEAD the line number of the start of the function
>>>>>>>>> [0]PETSC ERROR: is given.
>>>>>>>>> [0]PETSC ERROR: [0] TS user right-hand-side function line 0 unknownunknown
>>>>>>>>> [0]PETSC ERROR: [0] TSComputeRHSFunction line 282 src/ts/interface/ts.c
>>>>>>>>> [0]PETSC ERROR: [0] TSRkqs line 256 src/ts/impls/explicit/rk/rk.c
>>>>>>>>> [0]PETSC ERROR: [0] TSStep_Rk line 322 src/ts/impls/explicit/rk/rk.c
>>>>>>>>> [0]PETSC ERROR: [0] TSStep line 1520 src/ts/interface/ts.c
>>>>>>>>> [0]PETSC ERROR: --------------------------------------------
>>>>>>>>> [0]PETSC ERROR: User provided function() line 0 in unknown directory
>>>>>>>>> unknown file
>>>>>>>>> [0]PETSC ERROR: Signal received!
>>>>>>>>> [0]PETSC ERROR: !
>>>>>>>>> aborting job:
>>>>>>>>> application called MPI_Abort(MPI_COMM_WORLD, 59) - process 0
>>>>>>>>>
>>>>>>>>> On 3/3/06, Nils Erik Svangård <nilserik at gmail.com> wrote:
>>>>>>>>>> Hello again,
>>>>>>>>>>
>>>>>>>>>>> Is it just not compiling because PETSC_ERR_ARG_DOMAIN is not
>>>>>>>>>>> defined? Or does it still not work even when you have put the number in?
>>>>>>>>>>> What is the error? Or did you get it all working with SNES?
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> It is not compiling because PETSC_ERR_ARG_DOMAIN is not defined:
>>>>>>>>>>
>>>>>>>>>> error on line 585 of SNESG3D2.F: data type is undefined for variable
>>>>>>>>>> PETSC_ERR_ARG_DOMAIN
>>>>>>>>>>
>>>>>>>>>> I tried putting a number in, then it compiles but complains while
>>>>>>>>>> linking that the Push() and Pop() functions is not defined. I made a
>>>>>>>>>> workaround by adding a variable in a common block and setting it
>>>>>>>>>> before returning from a non physical value in the FormFunction. Now I
>>>>>>>>>> can compile and when there is a non-physical value it returns and
>>>>>>>>>> resumes with a smaller timestep.
>>>>>>>>>> SNES still give non physical values which are hard to add checks for
>>>>>>>>>> in the program (e.g sqrt(RO(L)-RO(L+1))).
>>>>>>>>>>
>>>>>>>>>> Did I understand correctly that SNES does a linesearch and probably
>>>>>>>>>> goes for a solution which isnt the one I looking for? Does SNES use
>>>>>>>>>> the linesearch algorithm when I use -snes_mf (which I use)?
>>>>>>>>>>
>>>>>>>>>>> It may work automatically with TS; you would just set TS with a
>>>>>>>>>>> smaller timestep and call TSSolve again?
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> OK, I'll add a check and put TSSolve in a while loop.
>>>>>>>>>>
>>>>>>>>>> My SNESSolve loop looks like this right now:
>>>>>>>>>> call VecCreateSeq(PETSC_COMM_SELF,N,x,ierr)
>>>>>>>>>> call VecDuplicate(x,r,ierr)
>>>>>>>>>> call VecDuplicate(x,xb,ierr)
>>>>>>>>>> call SNESCreate(PETSC_COMM_SELF,snes,ierr)
>>>>>>>>>> call SNESSetFunction(snes,r,FormFunction,PETSC_NULL_OBJECT,ierr)
>>>>>>>>>> call SNESSetFromOptions(snes,ierr)
>>>>>>>>>> call FormInitialGuess(x,ierr)
>>>>>>>>>> call VecCopy(x,xb,ierr)
>>>>>>>>>> write(6,*)zero,dt,tmax,i1000
>>>>>>>>>> step=0
>>>>>>>>>> timestep=dt
>>>>>>>>>> bang=0
>>>>>>>>>> C While loop
>>>>>>>>>> 10 if (step .le. 100) then
>>>>>>>>>> C call PetscExceptionPush(87,ierr)
>>>>>>>>>> C call PetscExceptionPush(PETSC_ERR_ARG_DOMAIN,ierr)
>>>>>>>>>> call SNESSolve(snes,PETSC_NULL_OBJECT,x,ierr)
>>>>>>>>>> ierr=bang
>>>>>>>>>> C call PetscExceptionPop(87,ierr2)
>>>>>>>>>> IF ( ierr .EQ. 87) THEN
>>>>>>>>>> timestep=timestep/2
>>>>>>>>>> call VecCopy(xb,x,ierr)
>>>>>>>>>> write(6,*) "No physical solution, trying",
>>>>>>>>>> . " with smaller timestep: ",timestep
>>>>>>>>>> bang=0
>>>>>>>>>> ELSE
>>>>>>>>>> call SNESGetConvergedReason(snes,reason,ierr)
>>>>>>>>>> IF ( reason .LT. 0 ) THEN
>>>>>>>>>> timestep=timestep/2
>>>>>>>>>> call VecCopy(xb,x,ierr)
>>>>>>>>>> write(6,*)"Solution diverged, trying with",
>>>>>>>>>> . " smaller timestep: ",timestep
>>>>>>>>>> ELSE
>>>>>>>>>> timestep=dt
>>>>>>>>>> step=step+1
>>>>>>>>>> call VecCopy(x,xb,ierr)
>>>>>>>>>> write(6,*) "Solve success, going for step: ",step
>>>>>>>>>> write(6,*) "Reason: ",reason," ierr: ",ierr
>>>>>>>>>> reason=0
>>>>>>>>>> ierr=0
>>>>>>>>>> ENDIF
>>>>>>>>>> ENDIF
>>>>>>>>>> goto 10
>>>>>>>>>> endif
>>>>>>>>>> C End While loop
>>>>>>>>>>
>>>>>>>>>> And the check in the FormFunction:
>>>>>>>>>>
>>>>>>>>>> if (ET(L) .LT. 0) then
>>>>>>>>>> ierr = 87
>>>>>>>>>> bang = 87
>>>>>>>>>> C SETERRQ(87,"Non physical value!",ierr)
>>>>>>>>>> return
>>>>>>>>>> elseif ( RO(L) .LT. 0 ) then
>>>>>>>>>> ierr = 87
>>>>>>>>>> bang = 87
>>>>>>>>>> return
>>>>>>>>>> endif
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> /nisse
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> Barry
>>>>>>>>>>>
>>>>>>>>>>> I'm adding a petscerror.h for Fortran that includes these values
>>>>>>>>>>> Sorry I forgot we hadn't given them for Fortran.
>>>>>>>>>>>
>>>>>>>>>>> On Thu, 2 Mar 2006, Nils Erik Svangård wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Hi again,
>>>>>>>>>>>> I realised that my implementation was a bit flawed so I have rewritten
>>>>>>>>>>>> it again, the push and pop() functions dont seem to work, and they are
>>>>>>>>>>>> keeping me from compiling the program, this is the main timestep loop:
>>>>>>>>>>>>
>>>>>>>>>>>> call VecCreateSeq(PETSC_COMM_SELF,N,x,ierr)
>>>>>>>>>>>> call VecDuplicate(x,r,ierr)
>>>>>>>>>>>> call VecDuplicate(x,xb,ierr)
>>>>>>>>>>>> call SNESCreate(PETSC_COMM_SELF,snes,ierr)
>>>>>>>>>>>> call SNESSetFunction(snes,r,FormFunction,PETSC_NULL_OBJECT,ierr)
>>>>>>>>>>>> call SNESSetFromOptions(snes,ierr)
>>>>>>>>>>>> call FormInitialGuess(x,ierr)
>>>>>>>>>>>> call VecCopy(x,xb,ierr)
>>>>>>>>>>>> write(6,*)zero,dt,tmax,i1000
>>>>>>>>>>>> step=0
>>>>>>>>>>>> timestep=dt
>>>>>>>>>>>> C While loop
>>>>>>>>>>>> 10 if (step .le. 100) then
>>>>>>>>>>>> call PetscExceptionPush(87,ierr)
>>>>>>>>>>>> call SNESSolve(snes,PETSC_NULL_OBJECT,x,ierr)
>>>>>>>>>>>> call PetscExceptionPop(87,ierr2)
>>>>>>>>>>>>
>>>>>>>>>>>> call SNESGetConvergedReason(snes,reason,ierr)
>>>>>>>>>>>> IF ( reason .LT. 0 ) THEN
>>>>>>>>>>>> timestep=timestep/2
>>>>>>>>>>>> VecCopy(xb,x,ierr)
>>>>>>>>>>>> write(6,*)"Solution diverged, trying with",
>>>>>>>>>>>> . " smaller timestep: ",timestep
>>>>>>>>>>>> ELSE
>>>>>>>>>>>> IF ( ierr .EQ. 87) THEN
>>>>>>>>>>>> timestep=timestep/2
>>>>>>>>>>>> VecCopy(xb,x,ierr)
>>>>>>>>>>>> write(6,*) "No physical solution, trying",
>>>>>>>>>>>> . " with smaller timestep: ",timestep
>>>>>>>>>>>> ELSE
>>>>>>>>>>>> timestep=dt
>>>>>>>>>>>> step=step+1
>>>>>>>>>>>> VecCopy(x,xb,ierr)
>>>>>>>>>>>> write(6,*) "Solve success, going for step: ",step
>>>>>>>>>>>> ENDIF
>>>>>>>>>>>> ENDIF
>>>>>>>>>>>> goto 10
>>>>>>>>>>>> endif
>>>>>>>>>>>> C End While loop
>>>>>>>>>>>>
>>>>>>>>>>>> And in my Formfunction I have added the following check:
>>>>>>>>>>>> if (ET(L) .LT. 0) then
>>>>>>>>>>>> ierr = 87
>>>>>>>>>>>> return
>>>>>>>>>>>> endif
>>>>>>>>>>>>
>>>>>>>>>>>> PETSC_ERR_ARG_DOMAIN didnt work: error on line 6500 of SNESG3D2.F:
>>>>>>>>>>>> data type is undefined for variable PETSC_ERR_ARG_DOMAIN
>>>>>>>>>>>> Even thought I had petsc.h included.
>>>>>>>>>>>>
>>>>>>>>>>>> Can I do this check when I use TS also? I have the sameproblem with
>>>>>>>>>>>> the values being negative when using TS.
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> /nisse
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On 2/27/06, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>> SNES works by computing p = -approxinv(J)*F(uold) and
>>>>>>>>>>>>> then does a line search on unew = uold + lambda*p to get the
>>>>>>>>>>>>> new u. First it uses a test value of 1 for lambda so it
>>>>>>>>>>>>> tries to compute F(uold + p). It is possible that uold + p
>>>>>>>>>>>>> has some "non-physical" values in it. There are two ways
>>>>>>>>>>>>> you can try handling it:
>>>>>>>>>>>>>
>>>>>>>>>>>>> 1) Before doing the linesearch SNES calls a "precheck" function,
>>>>>>>>>>>>> that can change the step if it decides there is a problem
>>>>>>>>>>>>> with the step (like it is too long). You can provide your
>>>>>>>>>>>>> own precheck function with SNESLineSearchSetPreCheck() it could,
>>>>>>>>>>>>> for example, shrink the Newton direction to make it remain physical.
>>>>>>>>>>>>>
>>>>>>>>>>>>> or 2) when your form function detects an illegal value it calls
>>>>>>>>>>>>> SETERRQ(PETSC_ERR_ARG_DOMAIN,"Nonphysical function input"); Note:
>>>>>>>>>>>>> this is before it takes the square root of the negative number,
>>>>>>>>>>>>> so check the number and call the error before calling SETERRQ().
>>>>>>>>>>>>> (If using Fortran then simply set ierr = PETSC_ERR_ARG_DOMAIN and
>>>>>>>>>>>>> then immediately return). Then replace your call to SNESSolve with
>>>>>>>>>>>>> ierr = PetscExceptionTry1(SNESSolve(snes,b,x),PETSC_ERR_ARG_DOMAIN);
>>>>>>>>>>>>> if (PetscExceptionCaught(ierr,PETSC_ERR_ARG_DOMAIN)) {
>>>>>>>>>>>>> /* this means your function found a non-physical value so
>>>>>>>>>>>>> cut your time-step and continue through the loop again. */
>>>>>>>>>>>>> Put code to do this here.
>>>>>>>>>>>>> }
>>>>>>>>>>>>> If using fortran then do
>>>>>>>>>>>>> call PetscExceptionPush(PETSC_ERR_ARG_DOMAIN,ierr)
>>>>>>>>>>>>> call SNESSolve(snes,b,x,ierr)
>>>>>>>>>>>>> call PetscExceptionPop(PETSC_ERR_ARG_DOMAIN,anotherierr)
>>>>>>>>>>>>> if (ierr == PETSC_ERR_ARG_DOMAIN) then
>>>>>>>>>>>>> non-physical value so cut the time-step and try again
>>>>>>>>>>>>> else ! everything is normal so take the next time-step
>>>>>>>>>>>>>
>>>>>>>>>>>>> Barry
>>>>>>>>>>>>>
>>>>>>>>>>>>> The Fortran interface may be missing PetscExceptionPush() and Pop()
>>>>>>>>>>>>> if so let us know and we'll provide the patch.
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Mon, 27 Feb 2006, Nils Erik Svangård wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Hi all,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I have problems solving some CFD problems using SNES and my custom
>>>>>>>>>>>>>> back-euler. I have 7 equations that I want to solve.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> First my FormFunction copies the values from the Vec that SNES uses to
>>>>>>>>>>>>>> the variables that my code use:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> RO(L)=xx(1,L)
>>>>>>>>>>>>>> RU(L)=xx(2,L)
>>>>>>>>>>>>>> RV(L)=xx(3,L)
>>>>>>>>>>>>>> RW(L)=xx(4,L)
>>>>>>>>>>>>>> ET(L)=xx(5,L)
>>>>>>>>>>>>>> RQ(L)= xx(6,L)
>>>>>>>>>>>>>> REPS(L)=xx(7,L)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Here I also print the values of ET(2) for debugging:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> write(6,*)"ET(2) = xx(5,2) : ",ET(2)," = ",xx(5,2)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Then I get the fluxes by calling custom functions
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> call AUXVR
>>>>>>>>>>>>>> call VGRAD
>>>>>>>>>>>>>> call FLUX
>>>>>>>>>>>>>> call KESRC
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Then I perform back-euler save the new value to so that I can use it
>>>>>>>>>>>>>> in the next iterationi (TSF(L) is Time step function, which is set by
>>>>>>>>>>>>>> hand and is the same for all L):
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> ff(1,L) = RO(L)-OLD(1,L)-TSF(L)*DRO(L)
>>>>>>>>>>>>>> ff(2,L) = RU(L)-OLD(2,L)-TSF(L)*DRU(L)
>>>>>>>>>>>>>> ff(3,L) = RV(L)-OLD(3,L)-TSF(L)*DRV(L)
>>>>>>>>>>>>>> ff(4,L) = RW(L)-OLD(4,L)-TSF(L)*DRW(L)
>>>>>>>>>>>>>> ff(5,L) = ET(L)-OLD(5,L)-TSF(L)*DET(L)
>>>>>>>>>>>>>> ff(6,L) = RQ(L)-OLD(6,L)-TSF(L)*DRQ(L)
>>>>>>>>>>>>>> ff(7,L) = REPS(L)-OLD(7,L)-TSF(L)*DREPS(L)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> And save the new value of RO-REPS to use in the next iteration of back-euler:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> OLD(1,L)=RO(L)
>>>>>>>>>>>>>> OLD(2,L)=RU(L)
>>>>>>>>>>>>>> OLD(3,L)=RV(L)
>>>>>>>>>>>>>> OLD(4,L)=RW(L)
>>>>>>>>>>>>>> OLD(5,L)=ET(L)
>>>>>>>>>>>>>> OLD(6,L)=RQ(L)
>>>>>>>>>>>>>> OLD(7,L)=REPS(L)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Here I print the values of L=2 as above for debugging:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> write(6,*)ff(5,2)," = ",ET(2),"-",OLD(5,2),"-",TSF(2),"*",DET(2)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The program exit abnormaly after 33 runs of the FormFunction. The
>>>>>>>>>>>>>> cause of this is that AUXVR tries to perform sqrt(ET(2)) when ET(2) is
>>>>>>>>>>>>>> negative, ET is the total energy and should never be negative. It
>>>>>>>>>>>>>> seems that all of a sudden the PETSc SNES solver decides to supply the
>>>>>>>>>>>>>> FormFunction with a negative ET value. I need help understanding why
>>>>>>>>>>>>>> and how to fix it (if it is fixable).
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Here is the output of:
>>>>>>>>>>>>>> write(6,*)"ET(2) = xx(5,2) : ",ET(2)," = ",xx(5,2)
>>>>>>>>>>>>>> Which is in the beginning of my FormFunction.
>>>>>>>>>>>>>> And:
>>>>>>>>>>>>>> write(6,*)ff(5,2)," = ",ET(2),"-",OLD(5,2),"-",TSF(2),"*",DET(2)
>>>>>>>>>>>>>> Which is in the end of my Formfunction.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> 1. ET(2) = xx(5,2) : 253250. = 253250.000000000
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 2. ET(2) = xx(5,2) : 253250. = 253250.000010259
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 3. ET(2) = xx(5,2) : 253250. = 253249.999999988
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4132419437260 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941324E+08
>>>>>>>>>>>>>> 4. ET(2) = xx(5,2) : 253250. = 253250.000048432
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 5. ET(2) = xx(5,2) : 253250. = 253249.999999872
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4177283437784 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941773E+08
>>>>>>>>>>>>>> 6. ET(2) = xx(5,2) : 253250. = 253250.000071113
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 7. ET(2) = xx(5,2) : 253250. = 253249.999980115
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4453347441010 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.944533E+08
>>>>>>>>>>>>>> 8. ET(2) = xx(5,2) : 253250. = 253250.000037298
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4082723436679 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.940827E+08
>>>>>>>>>>>>>> 9. ET(2) = xx(5,2) : 253250. = 253249.999942706
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4082723436679 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.940827E+08
>>>>>>>>>>>>>> 10. ET(2) = xx(5,2) : 253250. = 253249.999948703
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 11. ET(2) = xx(5,2) : 253250. = 253250.000007808
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.7283811474088 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.972838E+08
>>>>>>>>>>>>>> 12. ET(2) = xx(5,2) : 253250. = 253250.000018146
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 13. ET(2) = xx(5,2) : 253250. = 253250.000001865
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 28.3742819315846 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.837428E+08
>>>>>>>>>>>>>> 14. ET(2) = xx(5,2) : 253250. = 253249.999997296
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 15. ET(2) = xx(5,2) : 253250. = 253250.000000049
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 30.6548963582361 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -3.065490E+08
>>>>>>>>>>>>>> 16. ET(2) = xx(5,2) : 253250. = 253250.000022870
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 17. ET(2) = xx(5,2) : 253250. = 253249.999999716
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.5326051451209 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.953260E+08
>>>>>>>>>>>>>> 18. ET(2) = xx(5,2) : 253250. = 253250.000074328
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4165187437643 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941652E+08
>>>>>>>>>>>>>> 19. ET(2) = xx(5,2) : 253250. = 253250.000049809
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4085059436707 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.940851E+08
>>>>>>>>>>>>>> 20. ET(2) = xx(5,2) : 253250. = 253250.000019253
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 21. ET(2) = xx(5,2) : 253250. = 253250.000000189
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.8851075492403 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.988511E+08
>>>>>>>>>>>>>> 22. ET(2) = xx(5,2) : 253250. = 253249.999997897
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4085059436707 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.940851E+08
>>>>>>>>>>>>>> 23. ET(2) = xx(5,2) : 253250. = 253249.999975142
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.3961539435263 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.939615E+08
>>>>>>>>>>>>>> 24. ET(2) = xx(5,2) : 253250. = 253250.000018324
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4085059436707 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.940851E+08
>>>>>>>>>>>>>> 25. ET(2) = xx(5,2) : 253250. = 253249.999987073
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4165187437643 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941652E+08
>>>>>>>>>>>>>> 26. ET(2) = xx(5,2) : 253250. = 253249.999980982
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4165187437643 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941652E+08
>>>>>>>>>>>>>> 27. ET(2) = xx(5,2) : 253250. = 253249.999994645
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 28. ET(2) = xx(5,2) : 253250. = 253249.999962364
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4165187437643 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941652E+08
>>>>>>>>>>>>>> 29. ET(2) = xx(5,2) : 253250. = 253249.999999921
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 30. ET(2) = xx(5,2) : 253250. = 253250.000000058
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 28.4019971319085 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.840200E+08
>>>>>>>>>>>>>> 31. ET(2) = xx(5,2) : 253250. = 253250.000040348
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4085059436707 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.940851E+08
>>>>>>>>>>>>>> 32. ET(2) = xx(5,2) : 253250. = 253250.000005245
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 33. ET(2) = xx(5,2) : 253250. = 253250.000005245
>>>>>>>>>>>>>> ff(5,2) = ET(2)-OLD(5,2)-TSF(2)*DET(2) : 29.4126563437192 =
>>>>>>>>>>>>>> 253250. - 253250.000000000 - 1.000000E-07 * -2.941266E+08
>>>>>>>>>>>>>> 34. ET(2) = xx(5,2) : -848141. = -848141.388090847
>>>>>>>>>>>>>> --------------------------------------------------------------------------
>>>>>>>>>>>>>> Petsc Release Version 2.3.0, Patch 32, April, 26, 2005
>>>>>>>>>>>>>> See docs/changes/index.html for recent updates.
>>>>>>>>>>>>>> See docs/faq.html for hints about trouble shooting.
>>>>>>>>>>>>>> See docs/index.html for manual pages.
>>>>>>>>>>>>>> -----------------------------------------------------------------------
>>>>>>>>>>>>>> ./SNESG3D2 on a linux-gnu named sethnx004.vac.com by yy26539 Mon Feb
>>>>>>>>>>>>>> 27 14:21:13 2006
>>>>>>>>>>>>>> Libraries linked from /home/yy26539/work/NISSE/petsc-2.3.0/lib/linux-gnu
>>>>>>>>>>>>>> Configure run at Thu Oct 13 08:23:56 2005
>>>>>>>>>>>>>> Configure options --with-cc=gcc --with-fc="f77 -N109"
>>>>>>>>>>>>>> --download-mpich=1 --download-mpich-pm=gforker
>>>>>>>>>>>>>> --download-f-blas-lapack=1 --with-shared=0
>>>>>>>>>>>>>> -----------------------------------------------------------------------
>>>>>>>>>>>>>> [0]PETSC ERROR: Caught signal number 8 FPE: Floating Point
>>>>>>>>>>>>>> Exception,probably divide by zero
>>>>>>>>>>>>>> [0]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
>>>>>>>>>>>>>> [0]PETSC ERROR: likely location of problem given in stack below
>>>>>>>>>>>>>> [0]PETSC ERROR: --------------- Stack Frames ---------------
>>>>>>>>>>>>>> [0]PETSC ERROR: Note: The EXACT line numbers in the stack are not available,
>>>>>>>>>>>>>> [0]PETSC ERROR: INSTEAD the line number of the start of the function
>>>>>>>>>>>>>> [0]PETSC ERROR: is given.
>>>>>>>>>>>>>> [0]PETSC ERROR: [0] SNES user function line 0 unknownunknown
>>>>>>>>>>>>>> [0]PETSC ERROR: [0] SNESComputeFunction line 788 src/snes/interface/snes.c
>>>>>>>>>>>>>> [0]PETSC ERROR: [0] SNESLineSearchCubic line 514 src/snes/impls/ls/ls.c
>>>>>>>>>>>>>> [0]PETSC ERROR: --------------------------------------------
>>>>>>>>>>>>>> [0]PETSC ERROR: User provided function() line 0 in unknown directory
>>>>>>>>>>>>>> unknown file
>>>>>>>>>>>>>> [0]PETSC ERROR: Signal received!
>>>>>>>>>>>>>> [0]PETSC ERROR: !
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Suggestions and tips are very welcome!
>>>>>>>>>>>>>> /nisse
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> --
>>>>>>>>>>>>>> Nils-Erik Svang�rd
>>>>>>>>>>>>>> MSN: schweingaard at hotmail.com
>>>>>>>>>>>>>> Skype: schweingaard
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> --
>>>>>>>>>>>> Nils-Erik Svangård
>>>>>>>>>>>> MSN: schweingaard at hotmail.com
>>>>>>>>>>>> Skype: schweingaard
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> Nils-Erik Svangård
>>>>>>>>>> E-Mail: nilserik at gmail.com
>>>>>>>>>> MSN: schweingaard at hotmail.com
>>>>>>>>>> Skype: schweingaard
>>>>>>>>>> Mobil: +46-(0)70-3612178
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> Nils-Erik Svangård
>>>>>>>>> E-Mail: nilserik at gmail.com
>>>>>>>>> MSN: schweingaard at hotmail.com
>>>>>>>>> Skype: schweingaard
>>>>>>>>> Mobil: +46-(0)70-3612178
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Nils-Erik Svangård
>>>>>>> E-Mail: nilserik at gmail.com
>>>>>>> MSN: schweingaard at hotmail.com
>>>>>>> Skype: schweingaard
>>>>>>> Mobil: +46-(0)70-3612178
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Nils-Erik Svangård
>>>>> E-Mail: nilserik at gmail.com
>>>>> MSN: schweingaard at hotmail.com
>>>>> Skype: schweingaard
>>>>> Mobil: +46-(0)70-3612178
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>> Nils-Erik Svangård
>>> E-Mail: nilserik at gmail.com
>>> MSN: schweingaard at hotmail.com
>>> Skype: schweingaard
>>> Mobil: +46-(0)70-3612178
>>>
>>>
>>
>
>
> --
> Nils-Erik Svangård
> E-Mail: nilserik at gmail.com
> MSN: schweingaard at hotmail.com
> Skype: schweingaard
> Mobil: +46-(0)70-3612178
>
>
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