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Subject: Re: [OMPI devel] XML request
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-08-30 11:36:00

What if we instead offered a -xml-fd N option? I would rather not
create a file myself. However, since you are calling mpirun yourself,
this would allow you to create a pipe on your end, and then pass us
the write end of the pipe. We would then send all XML output down that

Jeff and I chatted about this and felt this might represent the
cleanest solution. Sound okay?

On Aug 28, 2009, at 6:33 AM, Greg Watson wrote:

> Ralph,
> Would this be doable? If we could guarantee that the only output
> that went to the file was XML then that would solve the problem.
> Greg
> On Aug 28, 2009, at 5:39 AM, Ashley Pittman wrote:
>> On Thu, 2009-08-27 at 23:46 -0400, Greg Watson wrote:
>>> I didn't realize it would be such a problem. Unfortunately there is
>>> simply no way to reliably parse this kind of output, because it is
>>> impossible to know what the error messages are going to be, and
>>> presumably they could include XML-like formatting as well. The whole
>>> point of the XML was to try and simplify the parsing of the mpirun
>>> output, but it now looks like it's actually more difficult.
>> I thought this might be difficult when I saw you were attempting it.
>> Let me tell you about what Valgrind does because they have similar
>> problems. Initially they just had added --xml=yes option which put
>> most
>> of the valgrind (as distinct from application) output in xml tags.
>> This
>> works for simple cases and if you mix it with --log-file=<filename>
>> it
>> keeps the valgrind output separate from the application output.
>> Unfortunately there are lots of places throughout the code where
>> developers have inserted print statements (in the valgrind case these
>> all go to the logfile) which means the xml is interspersed with non-
>> xml
>> output and hence impossibly to parse reliably.
>> What they have now done in the current release is to add a extra
>> --xml-file=<file> option as well as the --log-file=<file> option.
>> Now
>> in the simple case all output from a normal run goes well formatted
>> to
>> the xml file and the log file remains empty, any tool that wraps
>> around
>> valgrind can parse the xml which is guaranteed to be well formatted
>> and
>> it can detect the presence of other messages by looking for output in
>> the standard log file. The onus is then on tool writers to look at
>> the
>> remaining cases and decide if they are common or important enough to
>> wrap in xml and propose a patch or removal of the non-formatted
>> message
>> entirely.
>> The above seems to work well, having a separate log file for xml is a
>> huge step forward as it means whilst the xml isn't necessarily
>> complete
>> you can both parse it and are able to tell when it's missing
>> something.
>> Of course when looking at this level of tool integration it's
>> better to
>> use sockets that files (e.g. --xml-socket=localhost:1234 rather than
>> --xml-file=/tmp/app_XXXX.xml) but I'll leave that up to you.
>> I hope this gives you something to think over.
>> Ashley,
>> --
>> Ashley Pittman, Bath, UK.
>> Padb - A parallel job inspection tool for cluster computing
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