power-weight.h
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// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
//
// Cartesian power weight semiring operation definitions.
#ifndef FST_POWER_WEIGHT_H_
#define FST_POWER_WEIGHT_H_
#include <string>
#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, size_t n>
class PowerWeight : public TupleWeight<W, n> {
public:
using ReverseWeight = PowerWeight<typename W::ReverseWeight, n>;
PowerWeight() {}
explicit PowerWeight(const TupleWeight<W, n> &weight)
: TupleWeight<W, n>(weight) {}
template <class Iterator>
PowerWeight(Iterator begin, Iterator end) : TupleWeight<W, n>(begin, end) {}
// Initialize component `index` to `weight`; initialize all other components
// to `default_weight`
PowerWeight(size_t index, const W &weight,
const W &default_weight = W::Zero())
: TupleWeight<W, n>(index, weight, default_weight) {}
static const PowerWeight &Zero() {
static const PowerWeight zero(TupleWeight<W, n>::Zero());
return zero;
}
static const PowerWeight &One() {
static const PowerWeight one(TupleWeight<W, n>::One());
return one;
}
static const PowerWeight &NoWeight() {
static const PowerWeight no_weight(TupleWeight<W, n>::NoWeight());
return no_weight;
}
static const string &Type() {
static const string *const type =
new string(W::Type() + "_^" + std::to_string(n));
return *type;
}
static constexpr uint64 Properties() {
return W::Properties() &
(kLeftSemiring | kRightSemiring | kCommutative | kIdempotent);
}
PowerWeight Quantize(float delta = kDelta) const {
return PowerWeight(TupleWeight<W, n>::Quantize(delta));
}
ReverseWeight Reverse() const {
return ReverseWeight(TupleWeight<W, n>::Reverse());
}
};
// Semiring plus operation.
template <class W, size_t n>
inline PowerWeight<W, n> Plus(const PowerWeight<W, n> &w1,
const PowerWeight<W, n> &w2) {
PowerWeight<W, n> result;
for (size_t i = 0; i < n; ++i) {
result.SetValue(i, Plus(w1.Value(i), w2.Value(i)));
}
return result;
}
// Semiring times operation.
template <class W, size_t n>
inline PowerWeight<W, n> Times(const PowerWeight<W, n> &w1,
const PowerWeight<W, n> &w2) {
PowerWeight<W, n> result;
for (size_t i = 0; i < n; ++i) {
result.SetValue(i, Times(w1.Value(i), w2.Value(i)));
}
return result;
}
// Semiring divide operation.
template <class W, size_t n>
inline PowerWeight<W, n> Divide(const PowerWeight<W, n> &w1,
const PowerWeight<W, n> &w2,
DivideType type = DIVIDE_ANY) {
PowerWeight<W, n> result;
for (size_t i = 0; i < n; ++i) {
result.SetValue(i, Divide(w1.Value(i), w2.Value(i), type));
}
return result;
}
// Semimodule left scalar product.
template <class W, size_t n>
inline PowerWeight<W, n> Times(const W &scalar,
const PowerWeight<W, n> &weight) {
PowerWeight<W, n> result;
for (size_t i = 0; i < n; ++i) {
result.SetValue(i, Times(scalar, weight.Value(i)));
}
return result;
}
// Semimodule right scalar product.
template <class W, size_t n>
inline PowerWeight<W, n> Times(const PowerWeight<W, n> &weight,
const W &scalar) {
PowerWeight<W, n> result;
for (size_t i = 0; i < n; ++i) {
result.SetValue(i, Times(weight.Value(i), scalar));
}
return result;
}
// Semimodule dot product.
template <class W, size_t n>
inline W DotProduct(const PowerWeight<W, n> &w1, const PowerWeight<W, n> &w2) {
W result(W::Zero());
for (size_t i = 0; i < n; ++i) {
result = Plus(result, Times(w1.Value(i), w2.Value(i)));
}
return result;
}
// This function object generates weights over the Cartesian power of rank
// n over the underlying weight. This is intended primarily for testing.
template <class W, size_t n>
class WeightGenerate<PowerWeight<W, n>> {
public:
using Weight = PowerWeight<W, n>;
using Generate = WeightGenerate<W>;
explicit WeightGenerate(bool allow_zero = true) : generate_(allow_zero) {}
Weight operator()() const {
Weight result;
for (size_t i = 0; i < n; ++i) result.SetValue(i, generate_());
return result;
}
private:
Generate generate_;
};
} // namespace fst
#endif // FST_POWER_WEIGHT_H_