From c1a892e3fc38de076b4254e9993e9493a0d12b6c Mon Sep 17 00:00:00 2001
From: Patrick Simianer <p@simianer.de>
Date: Fri, 16 Oct 2015 10:26:47 +0200
Subject: dtrain sample.h: forest sampling, non-unique k-best sampling

---
 training/dtrain/sample.h | 132 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 102 insertions(+), 30 deletions(-)

diff --git a/training/dtrain/sample.h b/training/dtrain/sample.h
index 1249e372..bccc29b7 100644
--- a/training/dtrain/sample.h
+++ b/training/dtrain/sample.h
@@ -2,55 +2,127 @@
 #define _DTRAIN_SAMPLE_H_
 
 #include "kbest.h"
+#include "hg_sampler.h"
 
 #include "score.h"
 
 namespace dtrain
 {
 
-struct ScoredKbest : public DecoderObserver
+struct HypSampler : public DecoderObserver
 {
-  const size_t k_;
-  size_t feature_count_, effective_sz_;
-  vector<ScoredHyp> samples_;
-  Scorer* scorer_;
-  vector<Ngrams>* ref_ngs_;
-  vector<size_t>* ref_ls_;
+  size_t          feature_count, effective_size;
+  vector<Hyp>     sample;
+  vector<Ngrams>* reference_ngrams;
+  vector<size_t>* reference_lengths;
 
-  ScoredKbest(const size_t k, Scorer* scorer) :
-    k_(k), scorer_(scorer) {}
+  void
+  reset()
+  {
+    sample.clear();
+    effective_size = feature_count = 0;
+  }
+};
+
+struct KBestSampler : public HypSampler
+{
+  size_t  k;
+  bool    unique;
+  Scorer* scorer;
+
+  KBestSampler() {}
+  KBestSampler(const size_t k, Scorer* scorer) :
+    k(k), scorer(scorer) {}
 
   virtual void
   NotifyTranslationForest(const SentenceMetadata& /*smeta*/, Hypergraph* hg)
   {
-    samples_.clear(); effective_sz_ = feature_count_ = 0;
+    reset();
     KBest::KBestDerivations<vector<WordID>, ESentenceTraversal,
-      KBest::FilterUnique, prob_t, EdgeProb> kbest(*hg, k_);
-    for (size_t i = 0; i < k_; ++i) {
-      const KBest::KBestDerivations<vector<WordID>, ESentenceTraversal,
-            KBest::FilterUnique, prob_t, EdgeProb>::Derivation* d =
-              kbest.LazyKthBest(hg->nodes_.size() - 1, i);
+      KBest::FilterUnique, prob_t, EdgeProb> kbest(*hg, k);
+    for (size_t i=0; i<k; ++i) {
+      KBest::KBestDerivations<vector<WordID>, ESentenceTraversal,
+        KBest::FilterUnique, prob_t, EdgeProb>::Derivation* d =
+          kbest.LazyKthBest(hg->nodes_.size() - 1, i);
       if (!d) break;
-      ScoredHyp h;
-      h.w = d->yield;
-      h.f = d->feature_values;
-      h.model = log(d->score);
-      h.rank = i;
-      h.gold = scorer_->Score(h.w, *ref_ngs_, *ref_ls_);
-      samples_.push_back(h);
-      effective_sz_++;
-      feature_count_ += h.f.size();
+      sample.emplace_back(
+        d->yield,
+        d->feature_values,
+        log(d->score),
+        scorer->score(d->yield, *reference_ngrams, *reference_lengths),
+        i
+      );
+      effective_size++;
+      feature_count += sample.back().f.size();
     }
   }
+};
 
-  vector<ScoredHyp>* GetSamples() { return &samples_; }
-  inline void SetReference(vector<Ngrams>& ngs, vector<size_t>& ls)
+struct KBestNoFilterSampler : public KBestSampler
+{
+  size_t  k;
+  bool    unique;
+  Scorer* scorer;
+
+  KBestNoFilterSampler(const size_t k, Scorer* scorer) :
+    k(k), scorer(scorer) {}
+
+  virtual void
+  NotifyTranslationForest(const SentenceMetadata& /*smeta*/, Hypergraph* hg)
   {
-    ref_ngs_ = &ngs;
-    ref_ls_ = &ls;
+    reset();
+    KBest::KBestDerivations<vector<WordID>, ESentenceTraversal> kbest(*hg, k);
+    for (size_t i=0; i<k; ++i) {
+      const KBest::KBestDerivations<vector<WordID>, ESentenceTraversal>::Derivation* d =
+        kbest.LazyKthBest(hg->nodes_.size() - 1, i);
+      if (!d) break;
+      sample.emplace_back(
+        d->yield,
+        d->feature_values,
+        log(d->score),
+        scorer->score(d->yield, *reference_ngrams, *reference_lengths),
+        i
+      );
+      effective_size++;
+      feature_count += sample.back().f.size();
+    }
+  }
+};
+
+struct KSampler : public HypSampler
+{
+  const size_t k;
+  Scorer* scorer;
+  MT19937 rng;
+
+  explicit KSampler(const unsigned k, Scorer* scorer) :
+    k(k), scorer(scorer) {}
+
+  virtual void
+  NotifyTranslationForest(const SentenceMetadata& /*smeta*/, Hypergraph* hg)
+  {
+    reset();
+    std::vector<HypergraphSampler::Hypothesis> hs;
+    HypergraphSampler::sample_hypotheses(*hg, k, &rng, &hs);
+    for (size_t i=0; i<k; ++i) {
+      sample.emplace_back(
+        hs[i].words,
+        hs[i].fmap,
+        log(hs[i].model_score),
+        0,
+        0
+      );
+      effective_size++;
+      feature_count += sample.back().f.size();
+    }
+    sort(sample.begin(), sample.end(), [](Hyp& first, Hyp& second) {
+        return first.model > second.model;
+      });
+    for (unsigned i=0; i<sample.size(); i++) {
+      sample[i].rank=i;
+      scorer->score(sample[i].w, *reference_ngrams, *reference_lengths);
+    }
   }
-  inline size_t GetFeatureCount() { return feature_count_; }
-  inline size_t GetSize() { return effective_sz_; }
 };
 
 } // namespace
-- 
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