Dear Moses Users, I am trying to understand how the future cost is calculated.
>From http://www.statmt.org/moses/?n=Moses.Background: "The language model cost is usually calculated by a trigram language model. However, we do not know the preceding English words for a translation operation. Therefore, we approximate this cost by computing the language model score for the generated English words alone." Here English refers to the target language. - Why would already translated portions of the sentence contribute to the future cost? Is Hypothesis::CalcFutureScore function is retrieving the translation cost for each non-translated portion of the Hypothesis or does it (const SquareMatrix &futureScore) also include the LM cost? LanguageModel::CalcScore is adding ngram score to retFull score: fullScore += ngramScore; But then in TranslationOption::CalcScore, this is subtracted back: m_futureScore = retFullScore - ngramScore + m_scoreBreakdown.InnerProduct(StaticData::Instance().GetAllWeights()) - phraseSize * StaticData::Instance().GetWeightWordPenalty(); - Is the n-gram order (3) fixed for LM cost calculations used in future cost? It does not look so. It would be helpful if someone could clarify the future cost calculation further. Thanks, Ergun Ergun Bicici Koc University On Wed, Sep 24, 2008 at 5:46 PM, Philipp Koehn <[email protected]> wrote: > Hi, > > the future cost estimates includes an estimate of the phrase translation > cost > and language model cost, but not reordering costs. And yes, this is > implemented > as described in the Pharaoh manual. > > -phi > > On Wed, Sep 24, 2008 at 8:58 AM, Yee Seng Chan <[email protected]> > wrote: > > Hi list members, > > > > > > > > Inside TranslationOption.cpp::CalcScore(), m_futureScore is effectively: > > retFullScore - (PhraseSize*WordPenalty) > > > > (Kindly correct me if I'm wrong). > > > > > > > > What's the reasoning for using the above as futureScore? I know > retFullScore > > is n-gram score. Btw, does the approach here follows "Section 3.5 Future > > Cost Estimation" in the Pharaoh manual? > > > > > > > > Best regards, > > > > Yee Seng Chan > > > > > > > > _______________________________________________ > > 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 > >
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