[petsc-users] [petsc-maint #136411] PETSc Execution Error

[Barry Smith]

On Oct 21, 2012, at 9:01 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Sun, Oct 21, 2012 at 7:17 AM, Kirk, Benjamin (JSC-EG311) <
> benjamin.kirk-1 at nasa.gov> wrote:
> 
>> Aside from the debugger, you can enable floating point exceptions at
>> runtime if there is interest.
>> 
> 
> Thanks for this. There is code for Linux (using feenableexcept) and a bunch
> of esoteric architectures in petsc/src/sys/error/fp.c, activated when you
> pass -fp_trap. It looks like the xmmintrin option there wasn't correct.
> 
> Also, I see that the specific cause of the exception is actually retained
> in si_code, but with a different set of macros (FPE_FLTDIV) than
> feenableexcept (FE_DIVBYZERO).
> 
> Satish and Barry, is there any rationale for still using signal(2), which
> has been deprecated since 1988, instead of sigaction()?

   I think just 1) inertia and 2) if it ain't broke don't fix it (and break it in the process).  Presumably this could go on your always growing, never shrinking, projects list on bitbucket. Make sure to check what would happen with Microsoft Windows before making a change.


   Barry

> 
> 
>> 
>> Below is the code we use on mac/linux in libMesh to honor --enable-fpe on
>> the command line.  Note this was adapted from code originally provided from
>> INL by the Moose team, so thanks really goes to them!  We prefer the
>> feenableexcept() API on linux, but on the Mac you can get access to most of
>> the exceptions through the MMX instruction set.
>> 
>> Independent of the debugger it will still print the actual error and a
>> stack trace, which is often good enough to know what happened.
>> 
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> 
>> // floating-point exceptions
>> #ifdef LIBMESH_HAVE_FENV_H
>> #  include <fenv.h>
>> #endif
>> #ifdef LIBMESH_HAVE_XMMINTRIN_H
>> #  include <xmmintrin.h>
>> #endif
>> 
>> 
>> 
>>  /**
>>   * Floating point exception handler -- courtesy of Cody Permann & MOOSE
>> team
>>   */
>>  void libmesh_handleFPE(int /*signo*/, siginfo_t *info, void *
>> /*context*/)
>>  {
>>    std::cout << std::endl;
>>    std::cout << "Floating point exception signaled (";
>>    switch (info->si_code)
>>      {
>>      case FPE_INTDIV: std::cerr << "integer divide by zero"; break;
>>      case FPE_INTOVF: std::cerr << "integer overflow"; break;
>>      case FPE_FLTDIV: std::cerr << "floating point divide by zero"; break;
>>      case FPE_FLTOVF: std::cerr << "floating point overflow"; break;
>>      case FPE_FLTUND: std::cerr << "floating point underflow"; break;
>>      case FPE_FLTRES: std::cerr << "floating point inexact result"; break;
>>      case FPE_FLTINV: std::cerr << "invalid floating point operation";
>> break;
>>      case FPE_FLTSUB: std::cerr << "subscript out of range"; break;
>>      }
>>    std::cout << ")!" << std::endl;
>> 
>>    std::cout << std::endl;
>>    std::cout << "To track this down, compile debug version, start
>> debugger, set breakpoint for 'libmesh_handleFPE' and run" << std::endl;
>>    std::cout << "In gdb do:" << std::endl;
>>    std::cout << "  break libmesh_handleFPE" << std::endl;
>>    std::cout << "  run ..." << std::endl;
>>    std::cout << "  bt" << std::endl;
>> 
>>    libmesh_error();
>>  }
>> 
>> 
>>  /**
>>   * Toggle floating point exceptions -- courtesy of Cody Permann & MOOSE
>> team
>>   */
>>  void enableFPE(bool on)
>>  {
>> #if !defined(LIBMESH_HAVE_FEENABLEEXCEPT) &&
>> defined(LIBMESH_HAVE_XMMINTRIN_H)
>>    static int flags = 0;
>> #endif
>> 
>>    if (on)
>>      {
>>        struct sigaction new_action, old_action;
>> 
>> #ifdef LIBMESH_HAVE_FEENABLEEXCEPT
>>        feenableexcept(FE_DIVBYZERO | FE_INVALID);
>> #elif  LIBMESH_HAVE_XMMINTRIN_H
>>        flags = _MM_GET_EXCEPTION_MASK();           // store the flags
>>        _MM_SET_EXCEPTION_MASK(flags & ~_MM_MASK_INVALID);
>> #endif
>> 
>> 
>>        // Set up the structure to specify the new action.
>>        new_action.sa_sigaction = libmesh_handleFPE;
>>        sigemptyset (&new_action.sa_mask);
>>        new_action.sa_flags = SA_SIGINFO;
>> 
>>        sigaction (SIGFPE, NULL, &old_action);
>>        if (old_action.sa_handler != SIG_IGN)
>>          sigaction (SIGFPE, &new_action, NULL);
>>      }
>>    else
>>      {
>> #ifdef LIBMESH_HAVE_FEDISABLEEXCEPT
>>        fedisableexcept(FE_DIVBYZERO | FE_INVALID);
>> #elif  LIBMESH_HAVE_XMMINTRIN_H
>>        _MM_SET_EXCEPTION_MASK(flags);
>> #endif
>>        signal(SIGFPE, 0);
>>      }
>>  }
>> 
>