// itf/optimizable-itf.h
  
  // Copyright 2009-2011  Go Vivace Inc.;  Microsoft Corporation;  Georg Stemmer
  
  // 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_ITF_OPTIMIZABLE_ITF_H_
  #define KALDI_ITF_OPTIMIZABLE_ITF_H_
  
  #include "base/kaldi-common.h"
  #include "matrix/matrix-lib.h"
  
  namespace kaldi {
  /// @ingroup Interfaces
  /// @{
  
  /// OptimizableInterface provides
  /// a virtual class for optimizable objects.
  /// E.g. a class that computed a likelihood function and
  /// its gradient using some parameter
  /// that has to be optimized on data
  /// could inherit from it.
  template<class Real>
  class OptimizableInterface {
   public:
    /// computes gradient for a parameter params and returns it
    /// in gradient_out
    virtual void ComputeGradient(const Vector<Real> &params,
                                 Vector<Real> *gradient_out) = 0;
    /// computes the function value for a parameter params
    /// and returns it
    virtual Real ComputeValue(const Vector<Real> &params) = 0;
  
    virtual ~OptimizableInterface() {}
  };
  /// @} end of "Interfaces"
  } // end namespace kaldi
  
  #endif