Moses-support Digest, Vol 104, Issue 54

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Today's Topics:

1. Re: Major bug found in Moses (Read, James C)
2. Re: Major bug found in Moses (Marcin Junczys-Dowmunt)


----------------------------------------------------------------------

Message: 1
Date: Fri, 19 Jun 2015 14:15:49 +0000
From: "Read, James C" <jcread@essex.ac.uk>
Subject: Re: [Moses-support] Major bug found in Moses
To: Matthias Huck <mhuck@inf.ed.ac.uk>
Cc: "moses-support@mit.edu" <moses-support@mit.edu>, "Arnold, Doug"
<doug@essex.ac.uk>
Message-ID:
<DB3PR06MB0713A34728F9D6B05AC19F0985A40@DB3PR06MB0713.eurprd06.prod.outlook.com>

Content-Type: text/plain; charset="iso-8859-1"

I'm gonna try once more. This is what he said:

"the decoder's job is NOT to find the high quality translation"

The next time I have a panel of potential investors in front of me I'm gonna pass that line by them and see how it goes down. I stress the words HIGH QUALITY TRANSLATION.

Please promise me that the next time you put in a bid for funding you will guarantee your prospective funders that under no circumstances will you attempt to design a system which searches for HIGH QUALITY TRANSLATION.

James

________________________________________
From: Matthias Huck <mhuck@inf.ed.ac.uk>
Sent: Friday, June 19, 2015 5:08 PM
To: Read, James C
Cc: Hieu Hoang; moses-support@mit.edu; Arnold, Doug
Subject: Re: [Moses-support] Major bug found in Moses

Hi James,

Yes, he just said that.

The decoder's job is to find the hypothesis with the maximum model
score. That's one reason why your work is flawed. You did not care at
all whether your model score correlates with BLEU or not.

Cheers,
Matthias


On Fri, 2015-06-19 at 13:24 +0000, Read, James C wrote:
> I quote:
>
>
> "the decoder's job is NOT to find the high quality translation"
>
>
>
> Did you REALLY just say that?
>
>
> James
>
>
>
>
> ______________________________________________________________________
> From: Hieu Hoang <hieuhoang@gmail.com>
> Sent: Wednesday, June 17, 2015 9:00 PM
> To: Read, James C
> Cc: Kenneth Heafield; moses-support@mit.edu; Arnold, Doug
> Subject: Re: [Moses-support] Major bug found in Moses
>
> the decoder's job is NOT to find the high quality translation (as
> measured by bleu). It's job is to find translations with high model
> score.
>
>
> you need the tuning to make sure high quality translation correlates
> with high model score. If you don't tune, it's pot luck what quality
> you get.
>
>
> You should tune with the features you use
>
>
> Hieu Hoang
> Researcher
>
> New York University, Abu Dhabi
>
> http://www.hoang.co.uk/hieu
>
>
> On 17 June 2015 at 21:52, Read, James C <jcread@essex.ac.uk> wrote:
> The analogy doesn't seem to be helping me understand just how
> exactly it is a desirable quality of a TM to
>
> a) completely break down if no LM is used (thank you for
> showing that such is not always the case)
> b) be dependent on a tuning step to help it find the higher
> scoring translations
>
> What you seem to be essentially saying is that the TM cannot
> find the higher scoring translations because I didn't pretune
> the system to do so. And I am supposed to accept that such is
> a desirable quality of a system whose very job is to find the
> higher scoring translations.
>
> Further, I am still unclear which features you prequire a
> system to be tuned on. At the very least it seems that I have
> discovered the selection process that tuning seems to be
> making up for in some unspecified and altogether opaque way.
>
> James
>
>
> ________________________________________
> From: Hieu Hoang <hieuhoang@gmail.com>
> Sent: Wednesday, June 17, 2015 8:34 PM
> To: Read, James C; Kenneth Heafield; moses-support@mit.edu
> Cc: Arnold, Doug
> Subject: Re: [Moses-support] Major bug found in Moses
>
> 4 BLEU is nothing to sniff at :) I was answering Ken's tangent
> aspersion
> that LM are needed for tuning.
>
> I have some sympathy for you. You're looking at ways to
> improve
> translation by reducing the search space. I've bashed my head
> against
> this wall for a while as well without much success.
>
> However, as everyone is telling you, you haven't understood
> the role of
> tuning. Without tuning, you're pointing your lab rat to some
> random part
> of the search space, instead of away from the furry animal
> with whiskers
> and towards the yellow cheesy thing
>
> On 17/06/2015 20:45, Read, James C wrote:
> > Doesn't look like the LM is contributing all that much then
> does it?
> >
> > James
> >
> > ________________________________________
> > From: moses-support-bounces@mit.edu
> <moses-support-bounces@mit.edu> on behalf of Hieu Hoang
> <hieuhoang@gmail.com>
> > Sent: Wednesday, June 17, 2015 7:35 PM
> > To: Kenneth Heafield; moses-support@mit.edu
> > Subject: Re: [Moses-support] Major bug found in Moses
> >
> > On 17/06/2015 20:13, Kenneth Heafield wrote:
> >> I'll bite.
> >>
> >> The moses.ini files ship with bogus feature weights. One
> is required to
> >> tune the system to discover good weights for their system.
> You did not
> >> tune. The results of an untuned system are meaningless.
> >>
> >> So for example if the feature weights are all zeros, then
> the scores are
> >> all zero. The system will arbitrarily pick some awful
> translation from
> >> a large space of translations.
> >>
> >> The filter looks at one feature p(target | source). So now
> you've
> >> constrained the awful untuned model to a slightly better
> region of the
> >> search space.
> >>
> >> In other words, all you've done is a poor approximation to
> manually
> >> setting the weight to 1.0 on p(target | source) and the
> rest to 0.
> >>
> >> The problem isn't that you are running without a language
> model (though
> >> we generally do not care what happens without one). The
> problem is that
> >> you did not tune the feature weights.
> >>
> >> Moreover, as Marcin is pointing out, I wouldn't necessarily
> expect
> >> tuning to work without an LM.
> > Tuning does work without a LM. The results aren't half bad.
> fr-en
> > europarl (pb):
> > with LM: 22.84
> > retuned without LM: 18.33
> >> On 06/17/15 11:56, Read, James C wrote:
> >>> Actually the approximation I expect to be:
> >>>
> >>> p(e|f)=p(f|e)
> >>>
> >>> Why would you expect this to give poor results if the TM
> is well trained? Surely the results of my filtering
> experiments provve otherwise.
> >>>
> >>> James
> >>>
> >>> ________________________________________
> >>> From: moses-support-bounces@mit.edu
> <moses-support-bounces@mit.edu> on behalf of Rico Sennrich
> <rico.sennrich@gmx.ch>
> >>> Sent: Wednesday, June 17, 2015 5:32 PM
> >>> To: moses-support@mit.edu
> >>> Subject: Re: [Moses-support] Major bug found in Moses
> >>>
> >>> Read, James C <jcread@...> writes:
> >>>
> >>>> I have been unable to find a logical explanation for this
> behaviour other
> >>> than to conclude that there must be some kind of bug in
> Moses which causes a
> >>> TM only run of Moses to perform poorly in finding the most
> likely
> >>> translations according to the TM when
> >>>> there are less likely phrase pairs included in the
> race.
> >>> I may have overlooked something, but you seem to have
> removed the language
> >>> model from your config, and used default weights. your
> default model will
> >>> thus (roughly) implement the following model:
> >>>
> >>> p(e|f) = p(e|f)*p(f|e)
> >>>
> >>> which is obviously wrong, and will give you poor results.
> This is not a bug
> >>> in the code, but a poor choice of models and weights.
> Standard steps in SMT
> >>> (like tuning the model weights on a development set, and
> including a
> >>> language model) will give you the desired results.
> >>>
> >>> _______________________________________________
> >>> Moses-support mailing list
> >>> Moses-support@mit.edu
> >>> http://mailman.mit.edu/mailman/listinfo/moses-support
> >>>
> >>> _______________________________________________
> >>> Moses-support mailing list
> >>> Moses-support@mit.edu
> >>> http://mailman.mit.edu/mailman/listinfo/moses-support
> >> _______________________________________________
> >> Moses-support mailing list
> >> Moses-support@mit.edu
> >> http://mailman.mit.edu/mailman/listinfo/moses-support
> >>
> > --
> > Hieu Hoang
> > Researcher
> > New York University, Abu Dhabi
> > http://www.hoang.co.uk/hieu
> >
> > _______________________________________________
> > Moses-support mailing list
> > Moses-support@mit.edu
> > http://mailman.mit.edu/mailman/listinfo/moses-support
> > .
> >
>
> --
> Hieu Hoang
> Researcher
> New York University, Abu Dhabi
> http://www.hoang.co.uk/hieu
>
>
>
>
> _______________________________________________
> Moses-support mailing list
> Moses-support@mit.edu
> http://mailman.mit.edu/mailman/listinfo/moses-support



--
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.



------------------------------

Message: 2
Date: Fri, 19 Jun 2015 16:19:19 +0200
From: Marcin Junczys-Dowmunt <junczys@amu.edu.pl>
Subject: Re: [Moses-support] Major bug found in Moses
To: "Read, James C" <jcread@essex.ac.uk>
Cc: moses-support@mit.edu, Philipp Koehn <phi@jhu.edu>
Message-ID: <fff04a80e1d612f4e5e408c2c73738e0@amu.edu.pl>
Content-Type: text/plain; charset="utf-8"



German joke:

Ein Autofahrer h?rt im Radio die Durchsage: "Achtung! Achtung! Auf der
N9 kommt Ihnen ein Geisterfahrer entgegen. Fahren Sie bitte ganz rechts
und ?berholen Sie nicht!"
Der Autofahrer: "Was hei?t hier einer? Dutzende! Dutzende!"

Wdniu 2015-06-19 16:12, Read, James C napisa?(a):

> So we've gone from
>
> 1) Acknowledging that the search algorithm performs poorly with no LM, tuning or pruning despite the fact the search space clearly contains high quality translations
>
> 2) to a public display of en-masse reluctance to acknowledge that such is an undesirable quality of the system
>
> 3) to resorting to censorship not only in the literature but also on a public mailing list rather than acknowledge point 2.
>
> And your conclusion is that after being a witness to such behaviour I would still have a desire to contribute to this field?!? Why YES. I would love to keep banging my head against a brick wall. I have no other preferred past times.
>
> James
>
> -------------------------
>
> FROM: Lane Schwartz <dowobeha@gmail.com>
> SENT: Friday, June 19, 2015 5:04 PM
> TO: Read, James C
> CC: Philipp Koehn; Burger, John D.; moses-support@mit.edu
> SUBJECT: Re: [Moses-support] Major bug found in Moses
>
> James,
>
> You may see the techniques that exist as outdated, wrong-headed, and inefficient. You have the right to hold that opinion. It may even be that history proves you right. Progress in science is made by people posing questions - often questions that challenge the status quo - and then doing experiments to answer those questions.
>
> However, it is incumbent upon you, the proponent of a new idea, to design good experiments to attempt to prove or disprove your new hypothesis. Dispassionately showing the relative merits and shortcomings of your technique with the existing state of the art is part of that process.
>
> I, along with numerous other people on this list, have attempted in good faith to answer your questions, and to provide you with our perspective based on our collective understanding of the problem.
>
> You, in turn, have responded belligerently.
>
> I suggest that you have a frank conversation with your academic advisor or other appropriate mentor regarding your future. If you intend to pursue a successful career in science, academia, government, or industry, you would do well to reconsider the manner in which you interact with other people, especially people with whom you disagree.
>
> In the meantime, I would respectfully request that until you learn how to respectfully interact with other adults that you refrain from posting to this mailing list.
>
> Sincerely,
> Lane Schwartz
>
> On Fri, Jun 19, 2015 at 8:45 AM, Read, James C <jcread@essex.ac.uk> wrote:
>
> According to your book which I have on my desk the job of the TM is to model the most likely translations and the job of the decoder is to intelligently search the space of translations to find the most likely one/s (I'm paraphrasing of course).
>
> Would you like to retract that position and republish a next edition of your book which openly states that Moses when used with no LM or tuning or pruning can and should be expected to perform very poorly and select only the least likely translations?
>
> Don't you in the slightest find it worrying that like at least 90% of you code base could be thrown out of the window and high scoring results can be obtained with a simple phrase pair based rule based system?
>
> Which would you prefer? Would you prefer to consume computational resources calculating probabilites or get straight to the answer with simple logic and low computational requirements?
>
> BE HONEST!
>
> James
>
> -------------------------
>
> FROM: moses-support-bounces@mit.edu <moses-support-bounces@mit.edu> on behalf of Philipp Koehn <phi@jhu.edu>
> SENT: Thursday, June 18, 2015 9:39 PM
> TO: Burger, John D.
> CC: moses-support@mit.edu
>
> SUBJECT: Re: [Moses-support] Major bug found in Moses
>
> Hi,
>
> I am great fan of open source software, but there is a danger to
> view its inner workings as a black box - which leads to the
> strange theories of what is going on, instead of real understanding.
> But we can try to understand it.
>
> In the reported experiment, the language model was removed,
> while the rest of the system was left unchanged.
>
> The default untuned weights that train-model.perl assigns to a
> model are the following:
> WordPenalty0= -1
> PhrasePenalty0= 0.2
> TranslationModel0= 0.2 0.2 0.2 0.2
> Distortion0= 0.3
>
> Since no language model is used, a positive distortion cost will
> lead the decoder to not use any reordering at all. That's a
> good thing in this case.
>
> The word penalty is used to counteract the language model's
> preference for short translations. Unchecked, there is now a
> bias towards too long translations.
>
> Then there is the translation model with its equal weights for
> p(e|f) and p(f|e). The p(e|f) weight and scores are fine and well.
> However, p(f|e) only make sense if you have the Bayes theorem
> in your mind and a language model in your back. But in the
> reported setup, there is now a bias to translate into rare English
> phrases, since these will have high p(f|e) scores.
>
> My best guess is that the reported setup translates common
> function words (such as prepositions) into very long rare English
> phrases - word penalty likes it, p(f|e) likes it, p(e|f) does not mind
> enough - which produces a lot of rubbish.
>
> By filtering for p(e|f) those junky phrases are removed from the
> phrase table, restricting the decoder to more reasonable choices.
>
> I content that this is not a bug in the software, but a bug in usage.
>
> -phi
>
> On Thu, Jun 18, 2015 at 11:32 AM, Burger, John D. <john@mitre.org> wrote:
> On Jun 17, 2015, at 11:54, Read, James C <jcread@essex.ac.uk> wrote:
>
>> The question remains why isn't the system capable of finding the most likely translations without the LM?
>
> Even if it weren't ill-posed, I don't find this to be an interesting question at all. This is like trying to improve automobile transmissions by disabling the steering. These are the parts we have, and they all work together.
>
> It's not as if human translators don't use their own internal language models.
>
> - John Burger
> MITRE
>
>> Evidently, if you filter the phrase table then the LM is not as important as you might feel. The question remains why isn't the system capable of finding the most likely translations without the LM? Why do I need to filter to help the system find them? This is undesirable behaviour. Clearly a bug.
>>
>> I include the code I used for filtering. As you can see the 4th score only was used as a filtering criteria.
>>
>> #!/usr/bin/perl -w
>> #
>> # Program filters phrase table to leave only phrase pairs
>> # with probability above a threshold
>> #
>> use strict;
>> use warnings;
>> use Getopt::Long;
>>
>> my $phrase;
>> my $min;
>> my $phrase_table;
>> my $filtered_table;
>>
>> GetOptions( 'min=f' => $min,
>> 'out=s' => $filtered_table,
>> 'in=s' => $phrase_table);
>> die "ERROR: must give threshold and phrase table input file and output filen" unless ($min && $phrase_table && $filtered_table);
>> die "ERROR: file $phrase_table does not existn" unless (-e $phrase_table);
>> open (PHRASETABLE, "<$phrase_table") or die "FATAL: Could not open phrase table $phrase_tablen";;
>> open (FILTEREDTABLE, ">$filtered_table") or die "FATAL: Could not open phrase table $filtered_tablen";;
>>
>> while (my $line = <PHRASETABLE>)
>> {
>> chomp $line;
>> my @columns = split ('|||', $line);
>>
>> # check that file is a well formatted phrase table
>> if (scalar @columns < 4)
>> {
>> die "ERROR: input file is not a well formatted phrase table. A phrase table must have at least four colums each column separated by |||n";
>> }
>>
>> # get the probability and check it is less than the threshold
>> my @scores = split /s+/, $columns[2];
>> if ($scores[3] > $min)
>> {
>> print FILTEREDTABLE $line."n";;
>> }
>> }
>>
>>
>> > From: Matt Post <post@cs.jhu.edu>
>> Sent: Wednesday, June 17, 2015 5:25 PM
>> To: Read, James C
>> Cc: Marcin Junczys-Dowmunt; moses-support@mit.edu; Arnold, Doug
>> Subject: Re: [Moses-support] Major bug found in Moses
>>
>> I think you are misunderstanding how decoding works. The highest-weighted translation of each source phrase is not necessarily the one with the best BLEU score. This is why the decoder retains many options, so that it can search among them (together with their reorderings). The LM is an important component in making these selections.
>>
>> Also, how did you weight the many probabilities attached to each phrase (to determine which was the most probable)? The tuning phase of decoding selects weights designed to optimize BLEU score. If you weighted them evenly, that is going to exacerbate this experiment.
>>
>> matt
>>
>>
>>
>>> On Jun 17, 2015, at 10:22 AM, Read, James C <jcread@essex.ac.uk> wrote:
>>>
>>> All I did was break the link to the language model and then perform filtering. How is that a methodoligical mistake? How else would one test the efficacy of the TM in isolation?
>>>
>>> I remain convinced that this is undersirable behaviour and therefore a bug.
>>>
>>> James
>>>
>>>
>>> From: Marcin Junczys-Dowmunt <junczys@amu.edu.pl>
>>> Sent: Wednesday, June 17, 2015 5:12 PM
>>> To: Read, James C
>>> Cc: Arnold, Doug; moses-support@mit.edu
>>> Subject: Re: [Moses-support] Major bug found in Moses
>>>
>>> Hi James
>>> No, not at all. I would say that is expected behaviour. It's how search spaces and optimization works. If anything these are methodological mistakes on your side, sorry. You are doing weird thinds to the decoder and then you are surprised to get weird results from it.
>>> W dniu 2015-06-17 16:07, Read, James C napisa?(a):
>>>>
>>>> So, do we agree that this is undersirable behaviour and therefore a bug?
>>>>
>>>> James
>>>>
>>>> From: Marcin Junczys-Dowmunt <junczys@amu.edu.pl>
>>>> Sent: Wednesday, June 17, 2015 5:01 PM
>>>> To: Read, James C
>>>> Subject: Re: [Moses-support] Major bug found in Moses
>>>>
>>>> As I said. With an unpruned phrase table and an decoder that just optmizes some unreasonble set of weights all bets are off, so if you get very low BLEU point there, it's not surprising. It's probably jumping around in a very weird search space. With a pruned phrase table you restrict the search space VERY strongly. Nearly everything that will be produced is a half-decent translation. So yes, I can imagine that would happen.
>>>> Marcin
>>>> W dniu 2015-06-17 15:56, Read, James C napisa?(a):
>>>> You would expect an improvement of 37 BLEU points?
>>>>
>>>> James
>>>>
>>>>
>
>>>> From: Marcin Junczys-Dowmunt <junczys@amu.edu.pl>
>>>> Sent: Wednesday, June 17, 2015 4:32 PM
>>>> To: Read, James C
>>>> Cc: Moses-support@mit.edu; Arnold, Doug
>>>> Subject: Re: [Moses-support] Major bug found in Moses
>>>>
>>>> Hi James,
>>>> there are many more factors involved than just probability, for instance word penalties, phrase penalities etc. To be able to validate your own claim you would need to set weights for all those non-probabilities to zero. Otherwise there is no hope that moses will produce anything similar to the most probable translation. And based on that there is no surprise that there may be different translations. A pruned phrase table will produce naturally less noise, so I would say the behaviour you describe is quite exactly what I would expect to happen.
>>>> Best,
>>>> Marcin
>>>> W dniu 2015-06-17 15:26, Read, James C napisa?(a):
>>>> Hi all,
>>>>
>>>> I tried unsuccessfully to publish experiments showing this bug in Moses behaviour. As a result I have lost interest in attempting to have my work published. Nonetheless I think you all should be aware of an anomaly in Moses' behaviour which I have thoroughly exposed and should be easy enough for you to reproduce.
>>>>
>>>> As I understand it the TM logic of Moses should select the most likely translations according to the TM. I would therefore expect a run of Moses with no LM to find sentences which are the most likely or at least close to the most likely according to the TM.
>>>>
>>>> To test this behaviour I performed two runs of Moses. One with an unfiltered phrase table the other with a filtered phrase table which left only the most likely phrase pair for each source language phrase. The results were truly startling. I observed huge differences in BLEU score. The filtered phrase tables produced much higher BLEU scores. The beam size used was the default width of 100. I would not have been surprised in the differences in BLEU scores where minimal but they were quite high.
>>>>
>>>> I have been unable to find a logical explanation for this behaviour other than to conclude that there must be some kind of bug in Moses which causes a TM only run of Moses to perform poorly in finding the most likely translations according to the TM when there are less likely phrase pairs included in the race.
>>>>
>>>> I hope this information will be useful to the Moses community and that the cause of the behaviour can be found and rectified.
>>>>
>>>> James
>>>>
>>>> _______________________________________________
>>>> Moses-support mailing list
>>>>
>>>> Moses-support@mit.edu
>>>> http://mailman.mit.edu/mailman/listinfo/moses-support [1]
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>> _______________________________________________
>>> Moses-support mailing list
>>> Moses-support@mit.edu
>>> http://mailman.mit.edu/mailman/listinfo/moses-support [1]
>>
>> _______________________________________________
>> Moses-support mailing list
>> Moses-support@mit.edu
>> http://mailman.mit.edu/mailman/listinfo/moses-support [1]
>
> _______________________________________________
> Moses-support mailing list
> Moses-support@mit.edu
> http://mailman.mit.edu/mailman/listinfo/moses-support [1]
> _______________________________________________
> Moses-support mailing list
> Moses-support@mit.edu
> http://mailman.mit.edu/mailman/listinfo/moses-support [1]

--

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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