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+// tree/context-dep.h
+
+// Copyright 2009-2011  Microsoft Corporation
+
+// See ../../COPYING for clarification regarding multiple authors
+//
+// 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
+//
+// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
+// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
+// MERCHANTABLITY OR NON-INFRINGEMENT.
+// See the Apache 2 License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef KALDI_TREE_CONTEXT_DEP_H_
+#define KALDI_TREE_CONTEXT_DEP_H_
+
+#include "itf/context-dep-itf.h"
+#include "tree/event-map.h"
+#include "matrix/matrix-lib.h"
+#include "tree/cluster-utils.h"
+
+/*
+  This header provides the declarations for the class ContextDependency, which inherits
+  from the interface class "ContextDependencyInterface" in itf/context-dep-itf.h.
+  This is basically a wrapper around an EventMap.  The EventMap
+  (tree/event-map.h) declares most of the internals of the class, and the building routines are
+  in build-tree.h which uses build-tree-utils.h, which uses cluster-utils.h . */
+
+
+namespace kaldi {
+
+static const EventKeyType kPdfClass = -1;  // The "name" to which we assign the
+// pdf-class (generally corresponds ot position in the HMM, zero-based);
+// must not be used for any other event.  I.e. the value corresponding to
+// this key is the pdf-class (see hmm-topology.h for explanation of what this is).
+
+
+/* ContextDependency is quite a generic decision tree.
+
+   It does not actually do very much-- all the magic is in the EventMap object.
+   All this class does is to encode the phone context as a sequence of events, and
+   pass this to the EventMap object to turn into what it will interpret as a
+   vector of pdfs.
+
+   Different versions of the ContextDependency class that are written in the future may
+   have slightly different interfaces and pass more stuff in as events, to the
+   EventMap object.
+
+   In order to separate the process of training decision trees from the process
+   of actually using them, we do not put any training code into the ContextDependency class.
+ */
+class ContextDependency: public ContextDependencyInterface {
+ public:
+  virtual int32 ContextWidth() const { return N_; }
+  virtual int32 CentralPosition() const { return P_; }
+
+
+  /// returns success or failure; outputs pdf to pdf_id
+  virtual bool Compute(const std::vector<int32> &phoneseq,
+                       int32 pdf_class, int32 *pdf_id) const;
+
+  virtual int32 NumPdfs() const {
+    // this routine could be simplified to return to_pdf_->MaxResult()+1.  we're a
+    // bit more paranoid than that.
+    if (!to_pdf_) return 0;
+    EventAnswerType max_result = to_pdf_->MaxResult();
+    if (max_result < 0 ) return 0;
+    else return (int32) max_result+1;
+  }
+  virtual ContextDependencyInterface *Copy() const {
+    return new ContextDependency(N_, P_, to_pdf_->Copy());
+  }
+
+  /// Read context-dependency object from disk; throws on error
+  void Read (std::istream &is, bool binary);
+
+  // Constructor with no arguments; will normally be called
+  // prior to Read()
+  ContextDependency(): N_(0), P_(0), to_pdf_(NULL) { }
+
+  // Constructor takes ownership of pointers.
+  ContextDependency(int32 N, int32 P,
+                    EventMap *to_pdf):
+      N_(N), P_(P), to_pdf_(to_pdf) { }
+  void Write (std::ostream &os, bool binary) const;
+
+  ~ContextDependency() { if (to_pdf_ != NULL) delete to_pdf_; }
+
+  const EventMap &ToPdfMap() const { return *to_pdf_; }
+
+  /// GetPdfInfo returns a vector indexed by pdf-id, saying for each pdf which
+  /// pairs of (phone, pdf-class) it can correspond to.  (Usually just one).
+  /// c.f. hmm/hmm-topology.h for meaning of pdf-class.
+
+  void GetPdfInfo(const std::vector<int32> &phones,  // list of phones
+                  const std::vector<int32> &num_pdf_classes,  // indexed by phone,
+                  std::vector<std::vector<std::pair<int32, int32> > > *pdf_info)
+      const;
+
+ private:
+  int32 N_;  //
+  int32 P_;
+  EventMap *to_pdf_;  // owned here.
+
+  KALDI_DISALLOW_COPY_AND_ASSIGN(ContextDependency);
+};
+
+/// GenRandContextDependency is mainly of use for debugging.  Phones must be sorted and uniq
+/// on input.
+/// @param phones [in] A vector of phone id's [must be sorted and uniq].
+/// @param ensure_all_covered [in] boolean argument; if true,  GenRandContextDependency
+///        generates a context-dependency object that "works" for all phones [no gaps].
+/// @param num_pdf_classes [out] outputs a vector indexed by phone, of the number
+///          of pdf classes (e.g. states) for that phone.
+/// @return Returns the a context dependency object.
+ContextDependency *GenRandContextDependency(const std::vector<int32> &phones,
+                                            bool ensure_all_covered,
+                                            std::vector<int32> *num_pdf_classes);
+
+/// GenRandContextDependencyLarge is like GenRandContextDependency but generates a larger tree
+/// with specified N and P for use in "one-time" larger-scale tests.
+ContextDependency *GenRandContextDependencyLarge(const std::vector<int32> &phones,
+                                                 int N, int P,
+                                                 bool ensure_all_covered,
+                                                 std::vector<int32> *num_pdf_classes);
+
+// MonophoneContextDependency() returns a new ContextDependency object that
+// corresponds to a monophone system.
+// The map phone2num_pdf_classes maps from the phone id to the number of
+// pdf-classes we have for that phone (e.g. 3, so the pdf-classes would be
+// 0, 1, 2).
+
+ContextDependency*
+MonophoneContextDependency(const std::vector<int32> phones,
+                           const std::vector<int32> phone2num_pdf_classes);
+
+// MonophoneContextDependencyShared is as MonophoneContextDependency but lets
+// you define classes of phones which share pdfs (e.g. different stress-markers of a single
+// phone.)  Each element of phone_classes is a set of phones that are in that class.
+ContextDependency*
+MonophoneContextDependencyShared(const std::vector<std::vector<int32> > phone_classes,
+                                 const std::vector<int32> phone2num_pdf_classes);
+
+
+// Important note:
+// Statistics for training decision trees will be of type:
+// std::vector<std::pair<EventType, Clusterable*> >
+// We don't make this a typedef as it doesn't add clarity.
+// they will be sorted and unique on the EventType member, which
+// itself is sorted and unique on the name (see event-map.h).
+
+// See build-tree.h for functions relating to actually building the decision trees.
+
+
+
+
+}  // namespace Kaldi
+
+
+#endif