[developers] [incr() tsdb]/LKB memory allocation error

Ann Copestake aac10 at cl.cam.ac.uk
Tue Mar 15 22:17:25 CET 2016

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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