forward-backward algorithm

E880218

The forward-backward algorithm is a dynamic programming method for computing posterior state probabilities in hidden Markov models, widely used in tasks like sequence labeling and speech recognition.

All labels observed (4)

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Statements (47)

Predicate Object
instanceOf algorithm ⓘ
probabilistic graphical model algorithm ⓘ
appliesTo continuous-output hidden Markov models ⓘ
discrete hidden Markov models ⓘ
discrete-time sequences ⓘ
assumes conditional independence of observations given states ⓘ
first-order Markov chain over hidden states ⓘ
backwardVariableName beta ⓘ
basedOn Bayes rule ⓘ
linked to: Bayes’ theorem

Markov property ⓘ
canBeImplementedWith log-space computations ⓘ
scaling factors ⓘ
computes marginal state probabilities ⓘ
posterior state probabilities ⓘ
smoothed state probabilities ⓘ
field computational linguistics ⓘ
machine learning ⓘ
statistical signal processing ⓘ
forwardVariableName alpha ⓘ
goal avoid numerical underflow in probability products ⓘ
hasComponent backward pass ⓘ
forward pass ⓘ
introducedInContextOf hidden Markov models ⓘ
isSpecialCaseOf belief propagation ⓘ
sum-product algorithm ⓘ
operatesOn hidden state sequence ⓘ
observation sequence ⓘ
produces gamma probabilities ⓘ
xi probabilities ⓘ
relatedTo Baum-Welch algorithm ⓘ
Viterbi algorithm ⓘ
spaceComplexity O(T·N) ⓘ
timeComplexity O(T·N²) ⓘ
timeComplexityInWords linear in sequence length and quadratic in number of states ⓘ
usedFor biosequence analysis ⓘ
expectation step in Baum-Welch ⓘ
handwriting recognition ⓘ
named entity recognition ⓘ
part-of-speech tagging ⓘ
posterior decoding ⓘ
sequence labeling ⓘ
smoothing in time series ⓘ
speech recognition ⓘ
usedIn hidden Markov model ⓘ
linked to: Hidden Markov Model
uses emission probabilities ⓘ
initial state distribution ⓘ
transition probabilities ⓘ

How these facts were elicited

Referenced by (5)

Full triples — surface form annotated when it differs from this entity's canonical label.

Viterbi algorithm → comparedTo → forward-backward algorithm ⓘ
Hidden Markov Model → hasAlgorithm → Backward algorithm ⓘ
linked to: forward-backward algorithm
Hidden Markov Model → hasAlgorithm → Forward-Backward algorithm ⓘ
linked to: forward-backward algorithm
Baum–Welch algorithm → E-stepUses → forward–backward algorithm ⓘ
linked to: forward-backward algorithm
Baum–Welch algorithm → relatedTo → forward–backward algorithm ⓘ
linked to: forward-backward algorithm