src/include/fst/power-weight.h

// power-weight.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
// Cartesian power weight semiring operation definitions.

#ifndef FST_LIB_POWER_WEIGHT_H__
#define FST_LIB_POWER_WEIGHT_H__

#include <fst/tuple-weight.h>
#include <fst/weight.h>


namespace fst {

// Cartesian power semiring: W ^ n
// Forms:
//  - a left semimodule when W is a left semiring,
//  - a right semimodule when W is a right semiring,
//  - a bisemimodule when W is a semiring,
//    the free semimodule of rank n over W
// The Times operation is overloaded to provide the
// left and right scalar products.
template <class W, unsigned int n>
class PowerWeight : public TupleWeight<W, n> {
 public:
  using TupleWeight<W, n>::Zero;
  using TupleWeight<W, n>::One;
  using TupleWeight<W, n>::NoWeight;
  using TupleWeight<W, n>::Quantize;
  using TupleWeight<W, n>::Reverse;

  typedef PowerWeight<typename W::ReverseWeight, n> ReverseWeight;

  PowerWeight() {}

  PowerWeight(const TupleWeight<W, n> &w) : TupleWeight<W, n>(w) {}

  template <class Iterator>
  PowerWeight(Iterator begin, Iterator end) : TupleWeight<W, n>(begin, end) {}

  static const PowerWeight<W, n> &Zero() {
    static const PowerWeight<W, n> zero(TupleWeight<W, n>::Zero());
    return zero;
  }

  static const PowerWeight<W, n> &One() {
    static const PowerWeight<W, n> one(TupleWeight<W, n>::One());
    return one;
  }

  static const PowerWeight<W, n> &NoWeight() {
    static const PowerWeight<W, n> no_weight(TupleWeight<W, n>::NoWeight());
    return no_weight;
  }

  static const string &Type() {
    static string type;
    if (type.empty()) {
      string power;
      Int64ToStr(n, &power);
      type = W::Type() + "_^" + power;
    }
    return type;
  }

  static uint64 Properties() {
    uint64 props = W::Properties();
    return props & (kLeftSemiring | kRightSemiring |
                    kCommutative | kIdempotent);
  }

  PowerWeight<W, n> Quantize(float delta = kDelta) const {
    return TupleWeight<W, n>::Quantize(delta);
  }

  ReverseWeight Reverse() const {
    return TupleWeight<W, n>::Reverse();
  }
};


// Semiring plus operation
template <class W, unsigned int n>
inline PowerWeight<W, n> Plus(const PowerWeight<W, n> &w1,
                              const PowerWeight<W, n> &w2) {
  PowerWeight<W, n> w;
  for (size_t i = 0; i < n; ++i)
    w.SetValue(i, Plus(w1.Value(i), w2.Value(i)));
  return w;
}

// Semiring times operation
template <class W, unsigned int n>
inline PowerWeight<W, n> Times(const PowerWeight<W, n> &w1,
                               const PowerWeight<W, n> &w2) {
  PowerWeight<W, n> w;
  for (size_t i = 0; i < n; ++i)
    w.SetValue(i, Times(w1.Value(i), w2.Value(i)));
  return w;
}

// Semiring divide operation
template <class W, unsigned int n>
inline PowerWeight<W, n> Divide(const PowerWeight<W, n> &w1,
                                const PowerWeight<W, n> &w2,
                                DivideType type = DIVIDE_ANY) {
  PowerWeight<W, n> w;
  for (size_t i = 0; i < n; ++i)
    w.SetValue(i, Divide(w1.Value(i), w2.Value(i), type));
  return w;
}

// Semimodule left scalar product
template <class W, unsigned int n>
inline PowerWeight<W, n> Times(const W &s, const PowerWeight<W, n> &w) {
  PowerWeight<W, n> sw;
  for (size_t i = 0; i < n; ++i)
    sw.SetValue(i, Times(s, w.Value(i)));
  return w;
}

// Semimodule right scalar product
template <class W, unsigned int n>
inline PowerWeight<W, n> Times(const PowerWeight<W, n> &w, const W &s) {
  PowerWeight<W, n> ws;
  for (size_t i = 0; i < n; ++i)
    ws.SetValue(i, Times(w.Value(i), s));
  return w;
}

// Semimodule dot product
template <class W, unsigned int n>
inline W DotProduct(const PowerWeight<W, n> &w1,
                    const PowerWeight<W, n> &w2) {
  W w = W::Zero();
  for (size_t i = 0; i < n; ++i)
    w = Plus(w, Times(w1.Value(i), w2.Value(i)));
  return w;
}


}  // namespace fst

#endif  // FST_LIB_POWER_WEIGHT_H__