From 9f33503d74ac68893d3a927b8c6aad23392ead39 Mon Sep 17 00:00:00 2001 From: graehl Date: Mon, 5 Jul 2010 21:47:55 +0000 Subject: 0 bytes state for -o 1 (1gram) git-svn-id: https://ws10smt.googlecode.com/svn/trunk@143 ec762483-ff6d-05da-a07a-a48fb63a330f --- decoder/ff_lm.cc | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 62 insertions(+), 5 deletions(-) (limited to 'decoder') diff --git a/decoder/ff_lm.cc b/decoder/ff_lm.cc index 346b1fe6..7e3f6e2b 100644 --- a/decoder/ff_lm.cc +++ b/decoder/ff_lm.cc @@ -1,3 +1,5 @@ +//TODO: extra int in state to hold "GAP" token is not needed. if there are less than (N-1) words, then null terminate the e.g. left words. however, this would mean treating gapless items differently. not worth the potential bugs right now. + //TODO: allow features to reorder by heuristic*weight the rules' terminal phrases (or of hyperedges'). if first pass has pruning, then compute over whole ruleset as part of heuristic //TODO: verify that this is true: if ngram order is bigger than lm state's, then the longest possible ngram scores are still used. if you really want a lower order, a truncated copy of the LM should be small enough. otherwise, an option to null out words outside of the order's window would need to be implemented. @@ -201,6 +203,11 @@ class LanguageModelImpl { return ngram_.wordProb(word, (VocabIndex*)context); } + /// NOT a negative logp, i.e. should be worse prob = more negative. that's what SRI wordProb returns, fortunately. + inline double clamp(double logp) const { + return logp < floor_ ? floor_ : logp; + } + inline double LookupProbForBufferContents(int i) { // int k = i; cerr << "P("; while(buffer_[k] > 0) { std::cerr << TD::Convert(buffer_[k++]) << " "; } double p = WordProb(buffer_[i], &buffer_[i+1]); @@ -251,26 +258,34 @@ class LanguageModelImpl { return ProbNoRemnant(len - 1, len); } + //TODO: make sure this doesn't get used in FinalTraversal, or if it does, that it causes no harm. + + //TODO: use stateless_cost instead of ProbNoRemnant, check left words only. for items w/ fewer words than ctx len, how are they represented? kNONE padded? + + //TODO: make sure that Vocab_None is set to kNONE in srilm (-1), or that SRILM otherwise interprets -1 as a terminator and not a word double EstimateProb(const void* state) { + if (!order_) return 0.; int len = StateSize(state); // cerr << "residual len: " << len << endl; buffer_.resize(len + 1); buffer_[len] = kNONE; - const int* astate = reinterpret_cast(state); + const int* astate = reinterpret_cast(state); int i = len - 1; for (int j = 0; j < len; ++j,--i) buffer_[i] = astate[j]; return ProbNoRemnant(len - 1, len); } + // for (n-1 left words) and (n-1 right words) double FinalTraversalCost(const void* state) { + if (!order_) return 0.; int slen = StateSize(state); int len = slen + 2; // cerr << "residual len: " << len << endl; buffer_.resize(len + 1); buffer_[len] = kNONE; buffer_[len-1] = kSTART; - const int* astate = reinterpret_cast(state); + const int* astate = reinterpret_cast(state); int i = len - 2; for (int j = 0; j < slen; ++j,--i) buffer_[i] = astate[j]; @@ -279,8 +294,42 @@ class LanguageModelImpl { return ProbNoRemnant(len - 1, len); } + /// just how SRILM likes it: [rbegin,rend) is a phrase in reverse word order and null terminated so *rend=kNONE. return unigram score for rend[-1] plus + /// cost returned is some kind of log prob (who cares, we're just adding) + double stateless_cost(WordID *rbegin,WordID *rend) { + double sum=0; + for (;rend>rbegin;--rend) + sum+=clamp(WordProb(rend[-1],rend)); + return sum; + } + + //TODO: this would be a fine rule heuristic (for reordering hyperedges prior to rescoring. for now you can just use a same-lm-file -o 1 prelm-rescore :( + double stateless_cost(TRule const& rule) { + int len = rule.ELength(); // use a gap for each variable + buffer_.resize(len + 1); + buffer_[len] = kNONE; + WordID * const rend=&buffer_[0]+len; + WordID *r=rend; // append by *--r = x + const vector& e = rule.e(); + //SRILM is reverse order null terminated + //let's write down each phrase in reverse order and score it (note: we could lay them out consecutively then score them (we allocated enough buffer for that), but we won't actually use the whole buffer that way, since it wastes L1 cache. + double sum=0.; + for (unsigned j = 0; j < e.size(); ++j) { + if (e[j] < 1) { // variable + sum+=stateless_cost(r,rend); + r=rend; + } else { // terminal + *--r=e[j]; + } + } + // last phrase (if any) + return sum+stateless_cost(r,rend); + } + //NOTE: this is where the scoring of words happens (heuristic happens in EstimateProb) double LookupWords(const TRule& rule, const vector& ant_states, void* vstate) { + if (order_==0) + return stateless_cost(rule); int len = rule.ELength() - rule.Arity(); for (int i = 0; i < ant_states.size(); ++i) len += StateSize(ant_states[i]); @@ -328,8 +377,14 @@ class LanguageModelImpl { return sum; } +private: +public: + static int OrderToStateSize(int order) { - return ((order-1) * 2 + 1) * sizeof(WordID) + 1; + //TODO: should make the order==0 or not cases virtual overrides (performance gain) except then I have a 2x2 set of options against primary ngram owner vs. copy owner - which is easily factored for a performance loss. templates would be relatively concise and obviously lose no perf. honestly why am i even talking about performance? this is probably irrelevant. profile. + return order>1 ? + ((order-1) * 2 + 1) * sizeof(WordID) + 1 + : 0; } protected: @@ -375,6 +430,7 @@ LanguageModelImpl *make_lm_impl(int order, string const& f) if (f.find("lm://") == 0) { return new ClientLMI(order,f.substr(5)); } else if (ngs.have(f)) { + cerr<<"Reusing already loaded Ngram LM: "<