[developers] [incr() tsdb]/LKB memory allocation error
olzama at uw.edu
Thu Mar 24 22:55:59 CET 2016
Looking at the token chart, I see that I in fact have many lexical rules
for the same orthography, and that results in too many parses (a snippet of
the output is attached). For example, for this "a-tis-e" input that I am
trying, there are dozens lexical rules for a- and dozens for -a, and so the
combinations are too many. The reason for this is because the rules were
inferred automatically by a clustering algorithm, and I asked for many
clusters (there is a reason for asking for many clusters also: I am trying
to compare these results with another algorithm which happened to infer
many position classes, so I want my clustering to come up with the same
number and then to compare two grammars).
Is there a way to have the LKB stop after it found a parse, and not try
other possibilities? I tried doing that in itsdb (by turning off exhaustive
search and limiting the maximum number of analyses), but it still cannot
handle this large grammar for some reason...
On Thu, Mar 17, 2016 at 1:34 AM Ann Copestake <aac10 at cl.cam.ac.uk> wrote:
> So the process is running out of memory before hitting the limit on the
> number of chart edges, which stops processing a little more gracefully.
> The LKB batch parse process catches some errors in a way that allows the
> rest of the batch to continue. It may be that all that's happening is
> that the chart edge limit was set too high relative to the available
> memory, although it is possible that memory is being used in a way that
> isn't reflected by the edge limit, which is why I suggested also looking at
> the token chart. You could increase the amount of memory available to the
> process and see whether you can get your test set through, but unless
> that's the final test set and you don't intend to work on any more complex
> examples than the ones you have, that's only going to be a temporary
> I don't think it will matter whether you look at examples that can
> eventually be parsed, something that fails after a huge number of edges or
> something that causes the memory crash - your task is to find out whether
> there is something you can do to cut down the number of rule applications.
> The good news is that you won't need to find many cases of over-application
> to make a dramatic improvement. I think you will see the issues with the
> grammar when you look at a chart, even with a small edge limit.
> On 17/03/2016 01:55, Olga Zamaraeva wrote:
> Thank you Ann!
> I suppose I should try to pin down an input that can be successfully
> parsed, but does produce a huge chart. Of course my most pressing problem
> is not that some inputs are parsed with huge charts but that some inputs
> can never be parsed and break the system. But perhaps this is caused by the
> same problem (or feature) in the grammar.
> The LKB does give an error message, the same memory allocation error that
> comes through itsdb when that breaks (attached in the original email).
> On Tue, Mar 15, 2016 at 2:19 PM Ann Copestake <aac10 at cl.cam.ac.uk> wrote:
>> I would say that you should attempt to debug in the LKB. I don't know
>> exactly why [incr() tsdb] crashes while the LKB batch fails more
>> gracefully (does the LKB give an error message?) but you should try and
>> understand what's going on to give you such a huge chart. That's not to
>> say that it wouldn't be a good idea to know what the [incr() tsdb] issue
>> is, but it probably won't help you much ...
>> If you're using the LKB's morphophonology, you might want to look at the
>> token chart as well as the parse chart. This is more recent than the
>> book, so isn't documented, but if you have an expanded menu, I think it
>> shows up under Debug. You want the `print token chart' item, which will
>> output to the emacs window. Similarly, if you're trying to debug what's
>> going on and have an enormous parse chart, don't try and look at the
>> chart in a window, but use the `print chart' option. You would want to
>> reduce the maximum number of items to something a lot smaller than 20k
>> before you try that, though.
>> We should have a FAQ that says `ignore all the GC messages'. It's
>> really just a symptom of the underlying system running out of space -
>> nothing to do with the LKB or [incr() tsdb] as such. So there's not a
>> lot of enlightenment to be gained by understanding terms like tenuring ...
>> On 15/03/2016 19:55, Olga Zamaraeva wrote:
>> > Dear developers!
>> > I am trying to use the LKB and [incr() tsdb] to parse a list of verbs
>> > by a grammar of Chintang [ctn]. The language is polysynthetic, plus
>> > the grammar was created automatically using k-means clustering for the
>> > morphology section, so some of the position classes have lots and lots
>> > of inputs and lots and lots of lexical rule types and instances.
>> > I am running into a problem when [incr() tsdb] crashes because of a
>> > memory allocation error. If I don't use itsdb and just go with LKB
>> > batch parsing, it is more robust as it can catch the error and
>> > continue parsing, having reported a failure on the problematic item,
>> > but the problem is still there and the parses still fail.
>> > I am a fairly inexperienced user of both systems, so right now I am
>> > trying to understand what is the best way for me to:
>> > 1) debug the grammar with respect to the problem, i.e. what is it
>> > about the grammar exactly that causes the issues;
>> > 2) do something with itsdb so that perhaps this does not happen? Limit
>> > it somehow so that it doesn't try as much?
>> > Currently I am mostly just trying to filter out the problematic
>> > items... I also tried limiting the chart size to 30K, and that seems
>> > to have helped a little, but the crashes still happen on some items.
>> > If I limit the chart size to 20K, then it seems like maybe I can go
>> > through the test suite, but then my coverage suffers when I think it
>> > shouldn't: I think there are items which I can parse with 30K limit
>> > but not 20K... Is this the route I should be going in any case? Just
>> > optimizing for the chart size?.. Maybe 25K is my number :). The chart
>> > is the parse chart, is that correct? I need to understand what exactly
>> > makes the chart so huge in my case; how should I approach debugging
>> > that?..
>> > One specific question: what does "tenuring" mean with respect to
>> > garbage collection? Google doesn't know (nor does the manual, I think).
>> > Does anyone have any comment on any of these issues? The (very
>> > helpful) chapter on errors and debugging in Copestake (2002) book
>> > mostly talks about other types of issues such as type loading problems
>> > etc.. I also looked at what I found in ItsdbTop
>> > (http://moin.delph-in.net/ItsdbTop), and it does mention that on
>> > 32-bit systems memory problems are possible, but I think that note has
>> > to do with treebanking, and it doesn't really tell me much about what
>> > I should try in my case... I also looked thorough the itsdb manual
>> > (http://www.delph-in.net/itsdb/publications/manual.pdf) -- but it
>> > looks like some of the sections, specifically about debugging and
>> > options and parameters, are empty?
>> > Anyway, I would greatly appreciate any advice! I attach a picture of a
>> > running testsuite processing, to give an idea about the memory usage
>> > and the chart size, and of the error. It is possible that the grammar
>> > that I have is just not a usage scenario as far as itsdb is concerned,
>> > but I don't yet have a clear understanding of whether that's the case.
>> > Thanks!
>> > Olga
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