rustfst 0.13.1

Library for constructing, combining, optimizing, and searching weighted finite-state transducers (FSTs).
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152

use crate::algorithms::encode::EncodeType;
use crate::algorithms::encode::EncodeType::*;
use crate::algorithms::*;
use crate::fst_properties::FstProperties;
use crate::fst_traits::{AllocableFst, MutableFst};
use crate::semirings::{SemiringProperties, WeaklyDivisibleSemiring, WeightQuantize};
use crate::Semiring;
use anyhow::Result;

pub fn optimize<
    W: Semiring + WeaklyDivisibleSemiring + WeightQuantize,
    F: MutableFst<W> + AllocableFst<W>,
>(
    fst: &mut F,
) -> Result<()>
where
    W::ReverseWeight: WeightQuantize,
{
    if fst.properties().contains(FstProperties::ACCEPTOR) {
        optimize_acceptor(fst)
    } else {
        optimize_transducer(fst)
    }
}

fn determinize<
    W: Semiring + WeaklyDivisibleSemiring + WeightQuantize,
    F: MutableFst<W> + AllocableFst<W>,
>(
    fst: &mut F,
) -> Result<()> {
    *fst = determinize::determinize(fst)?;
    Ok(())
}

fn encode_deter_mini_decode<
    W: Semiring + WeaklyDivisibleSemiring + WeightQuantize,
    F: MutableFst<W> + AllocableFst<W>,
>(
    fst: &mut F,
    encoder: EncodeType,
) -> Result<()>
where
    W::ReverseWeight: WeightQuantize,
{
    let table = encode::encode(fst, encoder)?;
    determinize(fst)?;
    minimize(fst)?;
    encode::decode(fst, table)
}

fn optimize_transducer<
    W: Semiring + WeaklyDivisibleSemiring + WeightQuantize,
    F: MutableFst<W> + AllocableFst<W>,
>(
    fst: &mut F,
) -> Result<()>
where
    W::ReverseWeight: WeightQuantize,
{
    if !fst.properties().contains(FstProperties::NO_EPSILONS) {
        rm_epsilon::rm_epsilon(fst)?;
    }

    tr_sum(fst);

    if !W::properties().contains(SemiringProperties::IDEMPOTENT) {
        if !fst.properties().contains(FstProperties::I_DETERMINISTIC) {
            if fst.properties().contains(FstProperties::ACYCLIC) {
                encode_deter_mini_decode(fst, EncodeLabels)?;
            }
        } else {
            minimize(fst)?;
        }
    } else if !fst.properties().contains(FstProperties::I_DETERMINISTIC) {
        if !fst.properties().intersects(
            FstProperties::ACYCLIC | FstProperties::UNWEIGHTED | FstProperties::UNWEIGHTED_CYCLES,
        ) {
            encode_deter_mini_decode(fst, EncodeWeightsAndLabels)?;
            tr_sum(fst);
        } else {
            encode_deter_mini_decode(fst, EncodeLabels)?;
        }
    } else {
        minimize(fst)?;
    }

    Ok(())
}

fn optimize_acceptor<
    W: Semiring + WeaklyDivisibleSemiring + WeightQuantize,
    F: MutableFst<W> + AllocableFst<W>,
>(
    fst: &mut F,
) -> Result<()>
where
    W::ReverseWeight: WeightQuantize,
{
    if !fst.properties().contains(FstProperties::NO_EPSILONS) {
        rm_epsilon::rm_epsilon(fst)?;
    }
    tr_sum(fst);
    if !W::properties().contains(SemiringProperties::IDEMPOTENT) {
        if !fst.properties().contains(FstProperties::I_DETERMINISTIC) {
            if fst.properties().contains(FstProperties::ACYCLIC) {
                determinize(fst)?;
                minimize(fst)?;
            }
        } else {
            minimize(fst)?;
        }
    } else if !fst.properties().contains(FstProperties::I_DETERMINISTIC) {
        if !fst.properties().intersects(
            FstProperties::ACYCLIC | FstProperties::UNWEIGHTED | FstProperties::UNWEIGHTED_CYCLES,
        ) {
            encode_deter_mini_decode(fst, EncodeWeights)?;
            tr_sum(fst)
        } else {
            determinize(fst)?;
            minimize(fst)?;
        }
    } else {
        minimize(fst)?;
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::fst_traits::Fst;
    use crate::prelude::{TropicalWeight, VectorFst};
    use crate::SymbolTable;
    use proptest::prelude::any;
    use proptest::proptest;
    use std::sync::Arc;

    proptest! {
        #[test]
        fn test_proptest_optimize_keeps_symts(mut fst in any::<VectorFst::<TropicalWeight>>()) {
            let symt = Arc::new(SymbolTable::new());
            fst.set_input_symbols(Arc::clone(&symt));
            fst.set_output_symbols(Arc::clone(&symt));

            optimize(&mut fst).unwrap();

            assert!(fst.input_symbols().is_some());
            assert!(fst.output_symbols().is_some());
        }
    }
}