cdec --[prelm_]density_prune

git-svn-id: https://ws10smt.googlecode.com/svn/trunk@150 ec762483-ff6d-05da-a07a-a48fb63a330f

1 files changed, 25 insertions, 23 deletions

diff --git a/decoder/hg.cc b/decoder/hg.cc
index 70511c07..11dd6f44 100644
--- a/decoder/hg.cc
+++ b/decoder/hg.cc
@@ -175,10 +175,31 @@ void Hypergraph::PruneEdges(const std::vector<bool>& prune_edge, bool run_inside
   TopologicallySortNodesAndEdges(nodes_.size() - 1, &filtered);
 }
 
+void Hypergraph_finish_prune(Hypergraph &hg,vector<prob_t> const& io,double cutoff,vector<bool> const* preserve_mask,bool verbose=false)
+{
+  vector<bool> prune(hg.NumberOfEdges());
+  if (verbose) {
+    if (preserve_mask) cerr << preserve_mask->size() << " " << prune.size() << endl;
+    cerr<<"Finishing prune for "<<prune.size()<<" edges; CUTOFF=" << cutoff << endl;
+  }
+  unsigned pc = 0;
+  for (int i = 0; i < io.size(); ++i) {
+    const bool prune_edge = (io[i] < cutoff);
+    if (prune_edge) {
+      ++pc;
+      prune[i] = !(preserve_mask && (*preserve_mask)[i]);
+    }
+  }
+  if (verbose)
+    cerr << "Finished pruning; removed " << pc << "/" << io.size() << " edges\n";
+  hg.PruneEdges(prune);
+}
+
 void Hypergraph::DensityPruneInsideOutside(const double scale,
                                            const bool use_sum_prod_semiring,
                                            const double density,
-                                           const vector<bool>* preserve_mask) {
+                                           const vector<bool>* preserve_mask)
+{
   assert(density >= 1.0);
   const int plen = ViterbiPathLength(*this);
   vector<WordID> bp;
@@ -195,13 +216,7 @@ void Hypergraph::DensityPruneInsideOutside(const double scale,
   assert(edges_.size() == io.size());
   vector<prob_t> sorted = io;
   nth_element(sorted.begin(), sorted.begin() + rnum, sorted.end(), greater<prob_t>());
-  const double cutoff = sorted[rnum];
-  vector<bool> prune(edges_.size());
-  for (int i = 0; i < edges_.size(); ++i) {
-    prune[i] = (io[i] < cutoff);
-    if (preserve_mask && (*preserve_mask)[i]) prune[i] = false;
-  }
-  PruneEdges(prune);
+  Hypergraph_finish_prune(*this,io,sorted[rnum],preserve_mask);
 }
 
 void Hypergraph::BeamPruneInsideOutside(
@@ -209,7 +224,7 @@ void Hypergraph::BeamPruneInsideOutside(
     const bool use_sum_prod_semiring,
     const double alpha,
     const vector<bool>* preserve_mask) {
-  assert(alpha >= 0.0);
+  assert(alpha > 0.0);
   assert(scale > 0.0);
   vector<prob_t> io(edges_.size());
   if (use_sum_prod_semiring)
@@ -220,20 +235,7 @@ void Hypergraph::BeamPruneInsideOutside(
   prob_t best;  // initializes to zero
   for (int i = 0; i < io.size(); ++i)
     if (io[i] > best) best = io[i];
-  const prob_t aprob(exp(-alpha));
-  const prob_t cutoff = best * aprob;
-  // cerr << "aprob = " << aprob << "\t  CUTOFF=" << cutoff << endl;
-  vector<bool> prune(edges_.size());
-  //cerr << preserve_mask.size() << " " << edges_.size() << endl;
-  int pc = 0;
-  for (int i = 0; i < io.size(); ++i) {
-    const bool prune_edge = (io[i] < cutoff);
-    if (prune_edge) ++pc;
-    prune[i] = (io[i] < cutoff);
-    if (preserve_mask && (*preserve_mask)[i]) prune[i] = false;
-  }
-  // cerr << "Beam pruning " << pc << "/" << io.size() << " edges\n";
-  PruneEdges(prune);
+  Hypergraph_finish_prune(*this,io,best*exp(-alpha),preserve_mask);
 }
 
 void Hypergraph::PrintGraphviz() const {