[petsc-dev] -info from just one process?

[Stefano Zampini]

> I'm not talking about timings, I am talking about seeing where a code dies.
>

When codes die within the MPI implementation is basically impossible to
provide a backtrace from PETSc, but the MPI implementation may offer some
verbose messaging.
If this happens quite early in the code (and I presume here we are failing
somewhere in the 1-to-all pattern when distributing the plex data
structure) running with -log_trace may get you some insight on where this
is happening  (provided that the offending PETSc routine calls
LogEventBegin/End)

In my experience, the sad story is that when there are software
vendor failures with a large number of processes, I haven't found anything
more efficient than a few bisection steps with good old printfs....


>
>
>> As a side note, one would expect that this kind of behavior is consistent
>> across the library.
>> But in fact, it isn’t. If you do something like -sub_ksp_view_pmat file
>> with, for example, DD preconditioners, you end up with a single file with
>> all local matrices scrambled in.
>> It would be nice to have the same logic, i.e., file.%p, and be able to
>> filter ranks that actually print to file like you suggest.
>> These kind of options are less critical than -info so I can just insert
>> them in the option database after initialization, if rank == view_this_rank
>> PetscOptionsInsertString(), but doing that using command line arguments
>> would be easier and more elegant, IMO.
>>
>> Thanks,
>> Pierre
>>
>>   Barry
>>
>> On Apr 22, 2021, at 11:14 AM, Mark Adams <mfadams at lbl.gov> wrote:
>>
>> OK, so -info out.%p would do what I asked. Alas, what I really need it to
>> reduce the output with 128K processes.
>> Thanks,
>>
>> On Thu, Apr 22, 2021 at 11:54 AM Pierre Jolivet <pierre at joliv.et> wrote:
>>
>>>
>>>
>>> On 22 Apr 2021, at 5:33 PM, Jacob Faibussowitsch <jacob.fai at gmail.com>
>>> wrote:
>>>
>>> Not out of the box no. There is -info ::self which makes info only print
>>> from calls made on PETSC_COMM_SELF, but I don’t think that’s what you want.
>>> Best advice would be to print to a file and grep the file for any lines
>>> starting with the rank number you want.
>>>
>>>
>>> There is no need for grep, IMHO, just do -info file and then open file.%p
>>>
>>> Thanks,
>>> Pierre
>>>
>>> Best regards,
>>>
>>> Jacob Faibussowitsch
>>> (Jacob Fai - booss - oh - vitch)
>>>
>>> On Apr 22, 2021, at 10:16, Mark Adams <mfadams at lbl.gov> wrote:
>>>
>>> Can I make -info only print from one process?
>>> Mark
>>>
>>>
>>>
>>>
>>
>>

-- 
Stefano
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