[petsc-users] floating point exception… but only when >4 cores are used...

[Satish Balay]

On Fri, 27 Apr 2012, Andrew Spott wrote:

> I'm honestly stumped.
> 
> I have some petsc code that essentially just populates a matrix in parallel, then puts it in a file.  All my code that uses floating point computations is checked for NaN's and infinities and it doesn't seem to show up.  However, when I run it on more than 4 cores, I get floating point exceptions that kill the program.  I tried turning off the exceptions from petsc, but the program still dies from them, just without the petsc error message.
> 
> I honestly don't know where to go, I suppose I should attach a debugger, but I'm not sure how to do that for multi-processor code.

assuming you have X11 setup properly from compute nodes you can run
with the extra option '-start_in_debugger'

If X11 is not properly setup - and you'd like to run gdb on one of the
nodes [say node 14 where you see SEGV] - you can do:

-start_in-debugger noxterm -debugger_nodes 14

Or try valgrind

mpiexec -n 16 valgrind --tool=memcheck -q ./executable


For debugging - its best to install with --download-mpich [so that its
valgrind clean] - and run all mpi stuff on a single machine - [usually
X11 works well from a single machine.]

Satish

> 
> any ideas?  (long error message below):
> 
> -Andrew
> 
> [14]PETSC ERROR: ------------------------------------------------------------------------
> [14]PETSC ERROR: Caught signal number 8 FPE: Floating Point Exception,probably divide by zero
> [14]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
> [14]PETSC ERROR: or see http://www.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#valgrind[14]PETSC ERROR: or try http://valgrind.org on GNU/linux and Apple Mac OS X to find memory corruption errors
> [14]PETSC ERROR: likely location of problem given in stack below
> [14]PETSC ERROR: ---------------------  Stack Frames ------------------------------------
> [14]PETSC ERROR: Note: The EXACT line numbers in the stack are not available,
> [14]PETSC ERROR:       INSTEAD the line number of the start of the function
> [14]PETSC ERROR:       is given.
> [14]PETSC ERROR: --------------------- Error Message ------------------------------------
> [14]PETSC ERROR: Signal received!
> [14]PETSC ERROR: ------------------------------------------------------------------------
> [14]PE[15]PETSC ERROR: ------------------------------------------------------------------------
> [15]PETSC ERROR: Caught signal number 8 FPE: Floating Point Exception,probably divide by zero
> [15]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
> [15]PETSC ERROR: or see http://www.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#valgrind[15]PETSC ERROR: or try http://valgrind.org on GNU/linux and Apple Mac OS X to find memory corruption errors
> [15]PETSC ERROR: likely location of problem given in stack below
> [15]PETSC ERROR: ---------------------  Stack Frames ------------------------------------
> [15]PETSC ERROR: Note: The EXACT line numbers in the stack are not available,
> [15]PETSC ERROR:       INSTEAD the line number of the start of the function
> [15]PETSC ERROR:       is given.
> [15]PETSC ERROR: --------------------- Error Message ------------------------------------
> [15]PETSC ERROR: Signal received!
> [15]PETSC ERROR: ------------------------------------------------------------------------
> [15]PETSC ERROR: Petsc Release Version 3.2.0, Patch 6, Wed Jan 11 09:28:45 CST 2012 
> [14]PETSC ERROR: See docs/changes/index.html for recent updates.
> [14]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
> [14]PETSC ERROR: See docs/index.html for manual pages.
> [14]PETSC ERROR: ------------------------------------------------------------------------
> [14]PETSC ERROR: /home/becker/ansp6066/local/bin/finddme on a linux-gnu named photon9.colorado.edu by ansp6066 Fri Apr 27 18:01:55 2012
> [14]PETSC ERROR: Libraries linked from /home/becker/ansp6066/local/petsc-3.2-p6/lib
> [14]PETSC ERROR: Configure run at Mon Feb 27 11:17:14 2012
> [14]PETSC ERROR: Configure options --prefix=/home/becker/ansp6066/local/petsc-3.2-p6 --with-c++-support --with-fortran --with-mpi-dir=/usr/local/mpich2 --with-shared-libraries=0 --with-scalar-type=complex --with-blas-lapack-libs=/central/intel/mkl/lib/em64t/libmkl_core.a --with-clanguage=cxx
> [14]PETSC ERROR: ------------------------------------------------------------------------
> [14]TSC ERROR: Petsc Release Version 3.2.0, Patch 6, Wed Jan 11 09:28:45 CST 2012 
> [15]PETSC ERROR: See docs/changes/index.html for recent updates.
> [15]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
> [15]PETSC ERROR: See docs/index.html for manual pages.
> [15]PETSC ERROR: ------------------------------------------------------------------------
> [15]PETSC ERROR: /home/becker/ansp6066/local/bin/finddme on a linux-gnu named photon9.colorado.edu by ansp6066 Fri Apr 27 18:01:55 2012
> [15]PETSC ERROR: Libraries linked from /home/becker/ansp6066/local/petsc-3.2-p6/lib
> [15]PETSC ERROR: Configure run at Mon Feb 27 11:17:14 2012
> [15]PETSC ERROR: Configure options --prefix=/home/becker/ansp6066/local/petsc-3.2-p6 --with-c++-support --with-fortran --with-mpi-dir=/usr/local/mpich2 --with-shared-libraries=0 --with-scalar-type=complex --with-blas-lapack-libs=/central/intel/mkl/lib/em64t/libmkl_core.a --with-clanguage=cxx
> [15]PETSC ERROR: ------------------------------------------------------------------------
> [15]PETSC ERROR: User provided function() line 0 in unknown directory unknown file
> application called MPI_Abort(MPI_COMM_WORLD, 59) - process 14PETSC ERROR: User provided function() line 0 in unknown directory unknown file
> application called MPI_Abort(MPI_COMM_WORLD, 59) - process 15[0]0:Return code = 0, signaled with Interrupt