[petsc-users] Floating point exception

Fri Apr 24 15:01:15 CDT 2015

On 15-04-24 11:12 AM, Barry Smith wrote:
>> On Apr 24, 2015, at 1:05 PM, Danyang Su <danyang.su at gmail.com> wrote:
>>
>> Hi All,
>>
>> One of my case crashes because of floating point exception when using 4 processors, as shown below. But if I run this case with 1 processor, it works fine. I have tested the codes with around 100 cases up to 768 processors, all other cases work fine. I just wonder if this kind of error is caused because of NaN in jacobi matrix, RHS or preconditioner?
>     Yes, almost for sure it is one of these places.
>
>     First run the bad case with -fp_trap  if all goes well you'll see the function where the FPE is generated. Then run also with -start_in_debugger and
> type cont in all four debugger windows. When the FPE happens the debugger should stop showing exactly where the FPE happens.
>
>    Barry
Hi Barry,

If run with -fp_trap -start_in_debugger, I got the following error

[0]PETSC ERROR: *** unknown floating point error occurred ***
[0]PETSC ERROR: The specific exception can be determined by running in a 
debugger.  When the
[0]PETSC ERROR: debugger traps the signal, the exception can be found 
with fetestexcept(0x3d)
[0]PETSC ERROR: where the result is a bitwise OR of the following flags:
[0]PETSC ERROR: FE_INVALID=0x1 FE_DIVBYZERO=0x4 FE_OVERFLOW=0x8 
FE_UNDERFLOW=0x10 FE_INEXACT=0x20
[0]PETSC ERROR: Try option -start_in_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] PetscDefaultFPTrap line 379 
/home/dsu/Soft/PETSc/petsc-3.5.2/src/sys/error/fp.c
[0]PETSC ERROR: User provided function() line 0 in Unknown file trapped 
floating point error

Program received signal SIGABRT: Process abort signal.

Backtrace for this error:
#0  0x7F4FEAB1C7D7
#1  0x7F4FEAB1CDDE
#2  0x7F4FE9E1AD3F
#3  0x7F4FE9E1ACC9
#4  0x7F4FE9E1E0D7
#5  0x7F4FEB0B6DCB
#6  0x7F4FEB0B1825
#7  0x7F4FEB0B817F
#8  0x7F4FE9E1AD3F
#9  0x6972C8 in tprfrtlc_ at tprfrtlc.F90:2393 (discriminator 3)
#10  0x4C6C87 in gcreact_ at gcreact.F90:678
#11  0x707E19 in initicrt_ at initicrt.F90:589
#12  0x4F42D0 in initprob_ at initprob.F90:430
#13  0x5AAF72 in driver_pc at driver_pc.F90:438

I checked the code at  tprfrtlc.F90:2393,

         realbuffer_gb(1:nvars) = (/time,(c(ic),ic=1,nc-1),     &
                                    (cx(ix),ix=1,nxout)/)

All the values (time, c, cx) are reasonable, as shown below. The only 
possibility is that realbuffer_gb is in declared as real*4 if using sing 
precision output while time, c, cx are declared in real*8. I have a lot 
of similar data conversion from real*8 to real*4 output, other code does 
not return error.

  time   0.0000000000000000
  c           1   9.9999999999999995E-008
  c           2   3.1555251077549618E-003
  c           3   7.1657814842179362E-008
  c           4   1.0976214263087059E-067
  c           5   5.2879822292305797E-004
  c           6   9.9999999999999964E-005
  c           7   6.4055731968811337E-005
  c           8   3.4607572892578404E-020
  cx           1   3.4376650636008101E-005
  cx           2   7.3989678854017763E-012
  cx           3   9.5317170613607207E-012
  cx           4   2.2344525794718353E-015
  cx           5   3.0624685689695889E-008
  cx           6   1.0046157902783967E-007
  cx           7   1.5320169154914984E-004
  cx           8   8.6930292776346176E-014
  cx           9   3.5944267559348721E-005
  cx          10   3.0072645866951157E-018
  cx          11   2.3592486321095017E-013

Thanks,

Danyang

>
>> I can check all the entries of jacobi matrix to see if the value is valid, but this seems not a good idea as it takes a long time to reach this point. If I restart the simulation from a specified time (e.g., 7.685 in this case), then the error does not occur.
>>
>> Would you please give me any suggestion on debugging this case?
>>
>> Thanks and Regards,
>>
>> Danyang
>>
>>
>> timestep:    2730 time: 7.665E+00 years   delt: 1.000E-02 years iter:  1 max.sia: 0.000E+00 tol.sia: 0.000E+00
>> timestep:    2731 time: 7.675E+00 years   delt: 1.000E-02 years iter:  1 max.sia: 0.000E+00 tol.sia: 0.000E+00
>> timestep:    2732 time: 7.685E+00 years   delt: 1.000E-02 years iter:  1 max.sia: 0.000E+00 tol.sia: 0.000E+00
>> timestep:    2733 time: 7.695E+00 years   delt: 1.000E-02 years iter:  1 max.sia: 0.000E+00 tol.sia: 0.000E+00
>> timestep:    2734 time: 7.705E+00 years   delt: 1.000E-02 years iter:  1 max.sia: 0.000E+00 tol.sia: 0.000E+00
>> Reduce time step for reactive transport
>> timestep:    2734 time: 7.700E+00 years   delt: 5.000E-03 years iter:  1 max.sia: 0.000E+00 tol.sia: 0.000E+00
>> Reduce time step for reactive transport
>> timestep:    2734 time: 7.697E+00 years   delt: 2.500E-03 years iter:  1 max.sia: 0.000E+00 tol.sia: 0.000E+00
>> [1]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
>> [1]PETSC ERROR: Floating point exception
>> [2]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
>> [2]PETSC ERROR: Floating point exception
>> [2]PETSC ERROR: Vec entry at local location 0 is not-a-number or infinite at end of function: Parameter number 3
>> [2]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
>> [2]PETSC ERROR: Petsc Release Version 3.5.2, Sep, 08, 2014
>> [2]PETSC ERROR: [1]PETSC ERROR: Vec entry at local location 0 is not-a-number or infinite at end of function: Parameter number 3
>> [1]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
>> [1]PETSC ERROR: Petsc Release Version 3.5.2, Sep, 08, 2014
>> [1]PETSC ERROR: ../min3p_thcm_petsc_dbg on a linux-gnu-dbg named nwmop by dsu Thu Apr 23 15:38:52 2015
>> [1]PETSC ERROR: Configure options PETSC_ARCH=linux-gnu-dbg --with-cc=gcc --with-cxx=g++ --with-fc=gfortran --download-fblaslapack --download-mpich --download-mumps --download-hypre --download-superlu_dist --download-metis --download-parmetis --download-scalapack
>> [1]PETSC ERROR: #1 VecValidValues() line 34 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/vec/vec/interface/rvector.c
>> ../min3p_thcm_petsc_dbg on a linux-gnu-dbg named nwmop by dsu Thu Apr 23 15:38:52 2015
>> [2]PETSC ERROR: Configure options PETSC_ARCH=linux-gnu-dbg --with-cc=gcc --with-cxx=g++ --with-fc=gfortran --download-fblaslapack --download-mpich --download-mumps --download-hypre --download-superlu_dist --download-metis --download-parmetis --download-scalapack
>> [2]PETSC ERROR: #1 VecValidValues() line 34 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/vec/vec/interface/rvector.c
>> [2]PETSC ERROR: [1]PETSC ERROR: #2 PCApply() line 442 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/ksp/pc/interface/precon.c
>> [1]PETSC ERROR: #2 PCApply() line 442 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/ksp/pc/interface/precon.c
>> [2]PETSC ERROR: #3 KSP_PCApply() line 230 in /home/dsu/Soft/PETSc/petsc-3.5.2/include/petsc-private/kspimpl.h
>> #3 KSP_PCApply() line 230 in /home/dsu/Soft/PETSc/petsc-3.5.2/include/petsc-private/kspimpl.h
>> [1]PETSC ERROR: #4 KSPInitialResidual() line 63 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/ksp/ksp/interface/itres.c
>> [2]PETSC ERROR: #4 KSPInitialResidual() line 63 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/ksp/ksp/interface/itres.c
>> [1]PETSC ERROR: #5 KSPSolve_GMRES() line 234 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/ksp/ksp/impls/gmres/gmres.c
>> [2]PETSC ERROR: #5 KSPSolve_GMRES() line 234 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/ksp/ksp/impls/gmres/gmres.c
>> [2]PETSC ERROR: #6 KSPSolve() line 459 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/ksp/ksp/interface/itfunc.c
>> [1]PETSC ERROR: #6 KSPSolve() line 459 in /home/dsu/Soft/PETSc/petsc-3.5.2/src/ksp/ksp/interface/itfunc.c
>> ^C[mpiexec at nwmop] Sending Ctrl-C to processes as requested
>> [mpiexec at nwmop] Press Ctrl-C again to force abort