From 2b9cfc501f3d753c267a8273038cc36f40b488aa Mon Sep 17 00:00:00 2001
From: Chris Dyer <cdyer@cs.cmu.edu>
Date: Mon, 21 Mar 2011 22:10:02 -0400
Subject: add support for normalized 'summary features'- seemingly sound way of
 dealing with normalization problems in embedded crf translation models

---
 decoder/decoder.cc | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

(limited to 'decoder/decoder.cc')

diff --git a/decoder/decoder.cc b/decoder/decoder.cc
index 95ff6270..8a03c5c9 100644
--- a/decoder/decoder.cc
+++ b/decoder/decoder.cc
@@ -141,12 +141,13 @@ inline shared_ptr<FsaFeatureFunction> make_fsa_ff(string const& ffp,bool verbose
 // and then prune the resulting (rescored) hypergraph. All feature values from previous
 // passes are carried over into subsequent passes (where they may have different weights).
 struct RescoringPass {
-  RescoringPass() : density_prune(), beam_prune() {}
+  RescoringPass() : fid_summary(), density_prune(), beam_prune() {}
   shared_ptr<ModelSet> models;
   shared_ptr<IntersectionConfiguration> inter_conf;
   vector<const FeatureFunction*> ffs;
   shared_ptr<Weights> w;      // null == use previous weights
   vector<double> weight_vector;
+  int fid_summary;            // 0 == no summary feature
   double density_prune;       // 0 == don't density prune
   double beam_prune;          // 0 == don't beam prune
 };
@@ -155,6 +156,7 @@ ostream& operator<<(ostream& os, const RescoringPass& rp) {
   os << "[num_fn=" << rp.ffs.size();
   if (rp.inter_conf) { os << " int_alg=" << *rp.inter_conf; }
   if (rp.w) os << " new_weights";
+  if (rp.fid_summary) os << " summary_feature=" << FD::Convert(rp.fid_summary);
   if (rp.density_prune) os << " density_prune=" << rp.density_prune;
   if (rp.beam_prune) os << " beam_prune=" << rp.beam_prune;
   os << ']';
@@ -361,18 +363,21 @@ DecoderImpl::DecoderImpl(po::variables_map& conf, int argc, char** argv, istream
         ("weights,w",po::value<string>(),"Feature weights file (initial forest / pass 1)")
         ("feature_function,F",po::value<vector<string> >()->composing(), "Pass 1 additional feature function(s) (-L for list)")
         ("intersection_strategy,I",po::value<string>()->default_value("cube_pruning"), "Pass 1 intersection strategy for incorporating finite-state features; values include Cube_pruning, Full")
+        ("summary_feature", po::value<string>(), "Compute a 'summary feature' at the end of the pass (before any pruning) with name=arg and value=inside-outside/Z")
         ("density_prune", po::value<double>(), "Pass 1 pruning: keep no more than this many times the number of edges used in the best derivation tree (>=1.0)")
         ("beam_prune", po::value<double>(), "Pass 1 pruning: Prune paths from scored forest, keep paths within exp(alpha>=0)")
 
         ("weights2",po::value<string>(),"Optional pass 2")
         ("feature_function2",po::value<vector<string> >()->composing(), "Optional pass 2")
         ("intersection_strategy2",po::value<string>()->default_value("cube_pruning"), "Optional pass 2")
+        ("summary_feature2", po::value<string>(), "Optional pass 2")
         ("density_prune2", po::value<double>(), "Optional pass 2")
         ("beam_prune2", po::value<double>(), "Optional pass 2")
 
         ("weights3",po::value<string>(),"Optional pass 3")
         ("feature_function3",po::value<vector<string> >()->composing(), "Optional pass 3")
         ("intersection_strategy3",po::value<string>()->default_value("cube_pruning"), "Optional pass 3")
+        ("summary_feature3", po::value<string>(), "Optional pass 3")
         ("density_prune3", po::value<double>(), "Optional pass 3")
         ("beam_prune3", po::value<double>(), "Optional pass 3")
 
@@ -559,6 +564,7 @@ DecoderImpl::DecoderImpl(po::variables_map& conf, int argc, char** argv, istream
   for (int pass = 0; pass < MAX_PASSES; ++pass) {
     string ws = "weights" + StringSuffixForRescoringPass(pass);
     string ff = "feature_function" + StringSuffixForRescoringPass(pass);
+    string sf = "summary_feature" + StringSuffixForRescoringPass(pass);
     string bp = "beam_prune" + StringSuffixForRescoringPass(pass);
     string dp = "density_prune" + StringSuffixForRescoringPass(pass);
     bool first_pass_condition = ((pass == 0) && (conf.count(ff) || conf.count(bp) || conf.count(dp)));
@@ -583,6 +589,11 @@ DecoderImpl::DecoderImpl(po::variables_map& conf, int argc, char** argv, istream
           if (p->IsStateful()) { has_stateful = true; }
         }
       }
+      if (conf.count(sf)) {
+        rp.fid_summary = FD::Convert(conf[sf].as<string>());
+        assert(rp.fid_summary > 0);
+        // TODO assert that weights for this pass have coef(fid_summary) == 0.0?
+      }
       if (conf.count(bp)) { rp.beam_prune = conf[bp].as<double>(); }
       if (conf.count(dp)) { rp.density_prune = conf[dp].as<double>(); }
       int palg = (has_stateful ? 1 : 0);  // if there are no stateful featueres, default to FULL
@@ -794,6 +805,15 @@ bool DecoderImpl::Decode(const string& input, DecoderObserver* o) {
       cerr << "  " << passtr << " partition     log(Z): " << log(z) << endl;
     }
 
+    if (rp.fid_summary) {
+      Hypergraph::EdgeProbs posteriors;
+      const prob_t z = forest.ComputeEdgePosteriors(1.0, &posteriors);
+      if (!SILENT) { cerr << "  " << passtr << " adding summary feature " << FD::Convert(rp.fid_summary) << " log(Z)=" << log(z) << endl; }
+      assert(forest.edges_.size() == posteriors.size());
+      for (int i = 0; i < posteriors.size(); ++i)
+        forest.edges_[i].feature_values_.set_value(rp.fid_summary, log(posteriors[i] / z));
+    }
+
     string fullbp = "beam_prune" + StringSuffixForRescoringPass(pass);
     string fulldp = "density_prune" + StringSuffixForRescoringPass(pass);
     maybe_prune(forest,conf,fullbp.c_str(),fulldp.c_str(),passtr,srclen);
-- 
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