Thanks, Wilker. That does look promising. I love this little footnote from the paper: "We do not know if WLd is documented anywhere, but from inspection it is used in Moses (Koehn et al., 2007). This was confirmed by Philipp Koehn and Hieu Hoang (p.c.)."
On Fri, Dec 18, 2015 at 10:12 AM, Wilker Aziz <[email protected]> wrote: > Hi, > > I hope it is not too late to add to this discussion. > > If you are comfortable with weighted deduction, Adam Lopez's 2009 EACL > paper is very a good reference for phrase-based reordering spaces. If I > remember well the implementation in Moses does exactly what he shows with > the logic program WLd. > > http://alopez.github.io/papers/eacl2009-lopez.pdf > > Cheers, > > Wilker > > On 16 December 2015 at 00:56, Matthias Huck <[email protected]> wrote: > >> Hi Lane, >> >> Well, you can find excellent descriptions of phrase-based decoding >> algorithms in the literature, though possibly not all details of this >> specific implementation. >> >> I like this description: >> >> R. Zens, and H. Ney. Improvements in Dynamic Programming Beam Search for >> Phrase-based Statistical Machine Translation. In International Workshop >> on Spoken Language Translation (IWSLT), pages 195-205, Honolulu, HI, >> USA, October 2008. >> >> http://www.hltpr.rwth-aachen.de/publications/download/618/Zens-IWSLT-2008.pdf >> >> It's what's implemented in Jane, RWTH's open source statistical machine >> translation toolkit. >> >> J. Wuebker, M. Huck, S. Peitz, M. Nuhn, M. Freitag, J. Peter, S. >> Mansour, and H. Ney. Jane 2: Open Source Phrase-based and Hierarchical >> Statistical Machine Translation. In International Conference on >> Computational Linguistics (COLING), pages 483-491, Mumbai, India, >> December 2012. >> >> http://www.hltpr.rwth-aachen.de/publications/download/830/Wuebker-COLING-2012.pdf >> >> However, I believe that the distinction of coverage hypotheses and >> lexical hypotheses is a unique property of the RWTH systems. >> >> The formalization in the Zens & Ney paper is very nicely done. With hard >> distortion limits or coverage-based reordering constraints, you may need >> a few more steps in the algorithm. E.g., if you have a hard distortion >> limit, you will probably want to avoid leaving a gap and then extending >> your sequence in a way that puts your current position further away from >> the gap than your maximum jump width. Other people should know more >> about how exactly Moses' phrase-based decoder is dealing with this. >> >> I can recommend Richard Zens' PhD thesis as well. >> http://www.hltpr.rwth-aachen.de/publications/download/562/Zens--2008.pdf >> >> I also remember that the following publication from Microsoft Research >> is pretty helpful: >> >> Robert C. Moore and Chris Quirk, Faster Beam-Search Decoding for Phrasal >> Statistical Machine Translation, in Proceedings of MT Summit XI, >> European Association for Machine Translation, September 2007. >> http://research.microsoft.com/pubs/68097/mtsummit2007_beamsearch.pdf >> >> Cheers, >> Matthias >> >> >> >> On Tue, 2015-12-15 at 22:33 +0000, Hieu Hoang wrote: >> > I've been looking at this and it is surprisingly complicated. I think >> > the code is designed to predetermine if extending a hypothesis will >> > lead it down a path that won't ever be completed. >> > >> > >> > Don't know any slide that explains the reasoning, Philipp Koehn >> > explained it to me once and it seems pretty reasonable. >> > >> > >> > >> > I wouldn't mind seeing this code cleaned up a bit and abstracted and >> > formalised. I've made a start with the cleanup in my new decoder >> > >> > >> https://github.com/moses-smt/mosesdecoder/blob/perf_moses2/contrib/other-builds/moses2/Search/Search.cpp#L36 >> > Search::CanExtend() >> > >> > >> > There was an Aachen paper from years ago comparing different >> > distortion limit heuristics - can't remember the authors or title. >> > Maybe someone know more >> > >> > >> > >> > >> > >> > Hieu Hoang >> > http://www.hoang.co.uk/hieu >> > >> > >> > On 15 December 2015 at 20:59, Lane Schwartz <[email protected]> >> > wrote: >> > Hey all, >> > >> > >> > So the SearchNormal::ProcessOneHypothesis() method in >> > SearchNormal.cpp is responsible for taking an existing >> > hypothesis, creating all legal new extension hypotheses, and >> > adding those new hypotheses to the appropriate decoder >> > stacks. >> > >> > >> > First off, the method is actually reasonably well commented, >> > so kudos to whoever did that. :) >> > >> > >> > That said, does anyone happen to have any slides that actually >> > walk through this process, specifically slides that take into >> > account the interaction with the distortion limit? That >> > interaction is where most of the complexity of this method >> > comes from. I don't know about others, but even having a >> > pretty good notion of what's going on here, the discussion of >> > "the closest thing to the left" is still a bit opaque. >> > >> > >> > Anyway, if anyone knows of a good set of slides, or even a >> > good description in a paper, of what's going on here, I'd >> > appreciate any pointers. >> > >> > >> > Thanks, >> > Lane >> > >> > >> > >> > _______________________________________________ >> > Moses-support mailing list >> > [email protected] >> > http://mailman.mit.edu/mailman/listinfo/moses-support >> > >> > >> > >> > _______________________________________________ >> > Moses-support mailing list >> > [email protected] >> > http://mailman.mit.edu/mailman/listinfo/moses-support >> >> >> >> -- >> The University of Edinburgh is a charitable body, registered in >> Scotland, with registration number SC005336. >> >> _______________________________________________ >> Moses-support mailing list >> [email protected] >> http://mailman.mit.edu/mailman/listinfo/moses-support >> > > > > -- > Wilker Aziz > http://wilkeraziz.github.io <http://pers-www.wlv.ac.uk/~in1676/> > > > _______________________________________________ > Moses-support mailing list > [email protected] > http://mailman.mit.edu/mailman/listinfo/moses-support > > -- When a place gets crowded enough to require ID's, social collapse is not far away. It is time to go elsewhere. The best thing about space travel is that it made it possible to go elsewhere. -- R.A. Heinlein, "Time Enough For Love"
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