1 files changed, 146 insertions, 0 deletions
diff --git a/kaldi_io/src/tools/openfst/include/fst/reweight.h b/kaldi_io/src/tools/openfst/include/fst/reweight.h
new file mode 100644
index 0000000..c051c2a
--- /dev/null
+++ b/kaldi_io/src/tools/openfst/include/fst/reweight.h
@@ -0,0 +1,146 @@
+// reweight.h
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: allauzen@google.com (Cyril Allauzen)
+//
+// \file
+// Function to reweight an FST.
+
+#ifndef FST_LIB_REWEIGHT_H__
+#define FST_LIB_REWEIGHT_H__
+
+#include <vector>
+using std::vector;
+
+#include <fst/mutable-fst.h>
+
+
+namespace fst {
+
+enum ReweightType { REWEIGHT_TO_INITIAL, REWEIGHT_TO_FINAL };
+
+// Reweight FST according to the potentials defined by the POTENTIAL
+// vector in the direction defined by TYPE. Weight needs to be left
+// distributive when reweighting towards the initial state and right
+// distributive when reweighting towards the final states.
+//
+// An arc of weight w, with an origin state of potential p and
+// destination state of potential q, is reweighted by p\wq when
+// reweighting towards the initial state and by pw/q when reweighting
+// towards the final states.
+template <class Arc>
+void Reweight(MutableFst<Arc> *fst,
+              const vector<typename Arc::Weight> &potential,
+              ReweightType type) {
+  typedef typename Arc::Weight Weight;
+
+  if (fst->NumStates() == 0)
+    return;
+
+  if (type == REWEIGHT_TO_FINAL && !(Weight::Properties() & kRightSemiring)) {
+    FSTERROR() << "Reweight: Reweighting to the final states requires "
+               << "Weight to be right distributive: "
+               << Weight::Type();
+    fst->SetProperties(kError, kError);
+    return;
+  }
+
+  if (type == REWEIGHT_TO_INITIAL && !(Weight::Properties() & kLeftSemiring)) {
+    FSTERROR() << "Reweight: Reweighting to the initial state requires "
+               << "Weight to be left distributive: "
+               << Weight::Type();
+    fst->SetProperties(kError, kError);
+    return;
+  }
+
+  StateIterator< MutableFst<Arc> > sit(*fst);
+  for (; !sit.Done(); sit.Next()) {
+    typename Arc::StateId state = sit.Value();
+    if (state == potential.size())
+      break;
+    typename Arc::Weight weight = potential[state];
+    if (weight != Weight::Zero()) {
+      for (MutableArcIterator< MutableFst<Arc> > ait(fst, state);
+           !ait.Done();
+           ait.Next()) {
+        Arc arc = ait.Value();
+        if (arc.nextstate >= potential.size())
+          continue;
+        typename Arc::Weight nextweight = potential[arc.nextstate];
+        if (nextweight == Weight::Zero())
+          continue;
+        if (type == REWEIGHT_TO_INITIAL)
+          arc.weight = Divide(Times(arc.weight, nextweight), weight,
+                              DIVIDE_LEFT);
+        if (type == REWEIGHT_TO_FINAL)
+          arc.weight = Divide(Times(weight, arc.weight), nextweight,
+                              DIVIDE_RIGHT);
+        ait.SetValue(arc);
+      }
+      if (type == REWEIGHT_TO_INITIAL)
+        fst->SetFinal(state, Divide(fst->Final(state), weight, DIVIDE_LEFT));
+    }
+    if (type == REWEIGHT_TO_FINAL)
+      fst->SetFinal(state, Times(weight, fst->Final(state)));
+  }
+
+  // This handles elements past the end of the potentials array.
+  for (; !sit.Done(); sit.Next()) {
+    typename Arc::StateId state = sit.Value();
+    if (type == REWEIGHT_TO_FINAL)
+      fst->SetFinal(state, Times(Weight::Zero(), fst->Final(state)));
+  }
+
+  typename Arc::Weight startweight = fst->Start() < potential.size() ?
+      potential[fst->Start()] : Weight::Zero();
+  if ((startweight != Weight::One()) && (startweight != Weight::Zero())) {
+    if (fst->Properties(kInitialAcyclic, true) & kInitialAcyclic) {
+      typename Arc::StateId state = fst->Start();
+      for (MutableArcIterator< MutableFst<Arc> > ait(fst, state);
+           !ait.Done();
+           ait.Next()) {
+        Arc arc = ait.Value();
+        if (type == REWEIGHT_TO_INITIAL)
+          arc.weight = Times(startweight, arc.weight);
+        else
+          arc.weight = Times(
+              Divide(Weight::One(), startweight, DIVIDE_RIGHT),
+              arc.weight);
+        ait.SetValue(arc);
+      }
+      if (type == REWEIGHT_TO_INITIAL)
+        fst->SetFinal(state, Times(startweight, fst->Final(state)));
+      else
+        fst->SetFinal(state, Times(Divide(Weight::One(), startweight,
+                                          DIVIDE_RIGHT),
+                                   fst->Final(state)));
+    } else {
+      typename Arc::StateId state = fst->AddState();
+      Weight w = type == REWEIGHT_TO_INITIAL ?  startweight :
+                 Divide(Weight::One(), startweight, DIVIDE_RIGHT);
+      Arc arc(0, 0, w, fst->Start());
+      fst->AddArc(state, arc);
+      fst->SetStart(state);
+    }
+  }
+
+  fst->SetProperties(ReweightProperties(
+                         fst->Properties(kFstProperties, false)),
+                     kFstProperties);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_REWEIGHT_H_