[petsc-users] question about partitioning usage

[Jed Brown]

On Wed, Jan 25, 2012 at 15:28, Dominik Szczerba <dominik at itis.ethz.ch>wrote:

> It will take several minutes till xterm gdb windows will pop up, till
> I will manage to type "c+ENTER" into 64 windows on my 1024x768
> quadcore, and then till I find the right window where the executions
> stopped - but yes, it is definitely doable, and I already did that, as
> posted separately.
>

Why do you have to run on 64 processes to find out if ParMETIS is called?
Are you worried that there is code in PETSc that says

if (comm_size >= 64) do_crazy_things();


So run on a small number of processes (like 2 or 4) to see who calls
ParMETIS.


You can batch up setting of breakpoints

mpiexec -n 4 xterm -e gdb -ex 'b file.c:42' -ex r --args ./app -options
-for_petsc


These will run until they hit the breakpoint, no need to press "c".


If a partitioner is called to partition a global problem, then all ranks
must call it. In the case of ParMETIS errors, the output you showed told
you the rank. Suppose you want to look at ranks 13 and 59 of a 64-process
job.

run="./app -options -for_petsc"
dbg="xterm -e gdb -ex 'b file.c:42' -ex r --args $run"
mpiexec -n 13 $run : -n 1 $dbg : -n 45 $run : -n 1 $dbg : -n 4 $run
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