Map

Description

This operation transforms each arc and final state in the input FST. The transformation is specified by a function object called a mapper.

For instance, RmWeightMapper replaces the weight of every arc and final state by 1.

A list of available mappers and instructions on how to create them are given here.

Usage

template <class Arc, class Mapper> Map(MutableFst<Arc> *fst, Mapper *mapper);	[bad link?]
template <class Arc, class Mapper> Map(MutableFst<Arc> *fst, Mapper mapper);
template <class Arc, class Mapper> Map(const Fst<Arc> &ifst, MutableFst<Arc> *ofst, Mapper *mapper);
template <class Arc, class Mapper> Map(const Fst<Arc> &ifst, MutableFst<Arc> *ofst, Mapper mapper);
template <class Arc, class Mapper> MapFst<Arc>:: MapFst(const Fst<A> &fst, Mapper *mapper);
template <class Arc, class Mapper> MapFst<Arc>:: MapFst(const Fst<A> &fst, const Mapper &mapper);
fstmap [--opts] in.fst out.fst -delta (Comparison/quantization delta) type: double default: 0.0009765625 -map_type (Map operation, one of: "identity", "invert", "plus (--weight)", "quantize (--delta)", "rmweight", "superfinal", "times (--weight)" ) type: string default: "identity" -weight (Weight parameter) type: string default: ""

Example

A:

Map(&A, RmWeightMapper()):

Map(&A, RmWeightMapper<StdArc>());
Map(A, &B, RmWeightMapper<StdArc>());
MapFst B(A, RmWeightMapper<StdArc>());

fstmap --map_type=rmweight a.fst b.fst

Complexity

Map:

• Time: O(c*(V + E))
• Space: O(m)

where V = # of states, E = # of arcs in input FST, c = cost of processing one arc by the mapper and m = total memory usage for the mapper.

MapFst:

• Time: O(c*(v + e))
• Space: O(m)

where v = # of visited states, e = # of visited arcs in input FST, c = cost of processing one arc by the mapper and m = total memory usage for the mapper. Constant time and space to visit an input state or arc is assumed and exclusive of caching.

For instance in the case of RmWeightMapper, we have c = O(1) and m = O(1).

-- CyrilAllauzen - 04 Mar 2009