[src] Fix bug in pruned lattice rescoring when input lattice has epsilons (kaldi-asr#3190)

hainan-xv · danpovey · commit 584533433cd3 · 2019-03-31T23:21:00.000-04:00
diff --git a/src/lat/compose-lattice-pruned.cc b/src/lat/compose-lattice-pruned.cc
@@ -771,7 +771,14 @@ void PrunedCompactLatticeComposer::ProcessTransition(int32 src_composed_state,
   // Note: we expect that ilabel == olabel, since this is a CompactLattice, but this
   // may not be so if we extend this to work with Lattice.
   fst::StdArc lm_arc;
-  if (!det_fst_->GetArc(src_info->lm_state, olabel, &lm_arc)) {
+
+  // the input lattice might have epsilons
+  if (olabel == 0) {
+    lm_arc.ilabel = 0;
+    lm_arc.olabel = 0;
+    lm_arc.nextstate = src_info->lm_state;
+    lm_arc.weight = fst::StdArc::Weight(0.0);
+  } else if (!det_fst_->GetArc(src_info->lm_state, olabel, &lm_arc)) {
     // for normal language models we don't expect this to happen, but the
     // appropriate behavior is to do nothing; the composed arc does not exist,
     // so there is no arc to add and no new state to create.
