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---+ !OpenGrm !SFst Available Operations The following operations are provided for SFSTs. Care must be taken that the input FSTs meet the specified requirements (e.g. [[SFstGlossary#Canonical][canonical]], [[SFstGlossary#Backoff][backoff-complete]] or [[SFstGlossary#Normalized][normalized]]). The binary commands typically check their input requirements are satisfied or raise an error but the C++ versions may not check for efficiency (see the source code documentation for specific cases). | *Operation* | *Usage* | *Description* | *Complexity* | | <nop>Approx | <nop>Approx(ifst, &backoff_fst, phi_label, delta) | approximates a normalized stochastic FST wrt a provided [[SFstGlossary#BackoffDef][backoff-complete FST]]| same as [[http://www.openfst.org/twiki/bin/view/FST/ShortestDistanceDoc][ShortestDistance]] on the intersection of the input and output FSTs | | | sfstapprox[--phi_label=$l][--delta=$d] in.fst backoff.fst out.fst | | | | <nop>Count | | || | | sfstcount | | | | <nop>IsCanonical | <nop>IsCanonical(fst, phi_label) | checks the second property [[SFstLibrary#SFSTProperties][here]] holds for a weighted FST | Time, Space: _O(V + E)_ | | <nop>IsNormalized | <nop>IsNormalized(fst, phi_label, delta) | checks the two properties [[SFstLibrary#SFSTProperties][here]] hold for a weighted FST | Time, Space: _O(V + E)_ | | <nop>GlobalNormalize | <nop>GlobalNormalize(&fst, phi_label, delta) | globally normalizes, when possible<sup>1</sup>, a canonical weighted FST preserving total path weights (up to a global constant) | same as [[http://www.openfst.org/twiki/bin/view/FST/ShortestDistanceDoc][ShortestDistance]] | | | sfstnormalize [--method=global] [--phi_label=$l][--delta=$d] in.fst out.fst | | | | <nop>LocalNormalize | <nop>LocalNormalize(&fst) | locally normalizes, when possible, a canonical weighted FST preserving each state's out-going arc weights up to a state-specific constant | Time, Space: _O(V + E)_ | | | sfstnormalize -method=local in.fst out.fst | | | | <nop>NGramApprox | <nop>NGramApprox(ifst, &ofst, order, phi_label, delta) | approximates a normalized stochastic FST as an n-gram model (having =phi_labels= in [[NGramQuickTour#ModelFormat][OpenGrm NGram format]]) | same as [[http://www.openfst.org/twiki/bin/view/FST/ShortestDistanceDoc][ShortestDistance]] on the intersection of the input and output FSTs | | | sfstngramapprox [--order=$o][--phi_label=$l][--delta=$d] in.fst out.fst | | | | Perplexity | Perplexity(fst, phi_label, unknown_label, unknown_class_size) | computes perplexity for a stochastic FST | | | | sfstperplexity [--phi_label=$l] [-unknown_label=$u][--unknown_class_size=$s] in.fst test.far | (test sentences are in [[http://www.openfst.org/twiki/bin/view/FST/FstExtensions#FstArchive][FST archive]] format) | | | <nop>PhiNormalize | <nop>PhiNormalize(&fst, phi_label) | normalizes, when possible, a canonical weighted FST by only modifying the failure transitions | Time, Space: _O(V + E)_ | | | sfstnormalize --method=phi [-phi_label=$l][--delta=$d] in.fst out.fst | | | | <nop>RandGen| <nop>fst::RandGen(ifst, &ofst, <nop>fst::RandGenOptions<SFstArcSelector<Arc>>(...)) | randomly generates paths in a stochastic FST (correctly dealing with failure transitions) | see [[http://www.openfst.org/twiki/bin/view/FST/RandGenDoc][RandGen]] | | | sfstrandgen [--phi_label=$l] [--max_length=$l] [--npath=$n] [--seed=$s] in.fst out.fst | | | | <nop>Trim | <nop>Trim(&fst, phi_label) | removes useless states and transitions in stochastic automata (irrespective of weights) | Time, Space: _O(V + E * max-phi-order)_ | | | sfsttrim -phi_label=$l in.fst out.fst | | | --- <sup>1</sup>Possible when the sum of weight of all successful paths from the initial state is finite (and the input is [[http://www.openfst.org/twiki/bin/view/FST/FstGlossary#Trim][trim]]). %USERSIG{MichaelRiley - 2018-07-16}%
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Topic revision: r4 - 2019-07-18
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MichaelRiley
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