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language_model.cpp
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Jimmy O'Regan
Jim O'Regan
parent
5d8ede8c89
commit
a58a4e0f7b
@ -171,8 +171,10 @@ void LanguageModel::InitForWord(const WERD_CHOICE *prev_word,
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}
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}
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// Helper scans the collection of predecessors for competing siblings that
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// have the same letter with the opposite case, setting competing_vse.
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/**
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* Helper scans the collection of predecessors for competing siblings that
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* have the same letter with the opposite case, setting competing_vse.
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*/
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static void ScanParentsForCaseMix(const UNICHARSET& unicharset,
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LanguageModelState* parent_node) {
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if (parent_node == NULL) return;
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@ -200,8 +202,10 @@ static void ScanParentsForCaseMix(const UNICHARSET& unicharset,
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}
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}
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// Helper returns true if the given choice has a better case variant before
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// it in the choice_list that is not distinguishable by size.
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/**
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* Helper returns true if the given choice has a better case variant before
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* it in the choice_list that is not distinguishable by size.
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*/
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static bool HasBetterCaseVariant(const UNICHARSET& unicharset,
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const BLOB_CHOICE* choice,
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BLOB_CHOICE_LIST* choices) {
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@ -222,27 +226,32 @@ static bool HasBetterCaseVariant(const UNICHARSET& unicharset,
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return false; // Should never happen, but just in case.
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}
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// UpdateState has the job of combining the ViterbiStateEntry lists on each
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// of the choices on parent_list with each of the blob choices in curr_list,
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// making a new ViterbiStateEntry for each sensible path.
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// This could be a huge set of combinations, creating a lot of work only to
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// be truncated by some beam limit, but only certain kinds of paths will
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// continue at the next step:
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// paths that are liked by the language model: either a DAWG or the n-gram
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// model, where active.
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// paths that represent some kind of top choice. The old permuter permuted
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// the top raw classifier score, the top upper case word and the top lower-
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// case word. UpdateState now concentrates its top-choice paths on top
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// lower-case, top upper-case (or caseless alpha), and top digit sequence,
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// with allowance for continuation of these paths through blobs where such
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// a character does not appear in the choices list.
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// GetNextParentVSE enforces some of these models to minimize the number of
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// calls to AddViterbiStateEntry, even prior to looking at the language model.
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// Thus an n-blob sequence of [l1I] will produce 3n calls to
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// AddViterbiStateEntry instead of 3^n.
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// Of course it isn't quite that simple as Title Case is handled by allowing
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// lower case to continue an upper case initial, but it has to be detected
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// in the combiner so it knows which upper case letters are initial alphas.
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/**
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* UpdateState has the job of combining the ViterbiStateEntry lists on each
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* of the choices on parent_list with each of the blob choices in curr_list,
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* making a new ViterbiStateEntry for each sensible path.
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*
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* This could be a huge set of combinations, creating a lot of work only to
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* be truncated by some beam limit, but only certain kinds of paths will
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* continue at the next step:
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* - paths that are liked by the language model: either a DAWG or the n-gram
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* model, where active.
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* - paths that represent some kind of top choice. The old permuter permuted
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* the top raw classifier score, the top upper case word and the top lower-
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* case word. UpdateState now concentrates its top-choice paths on top
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* lower-case, top upper-case (or caseless alpha), and top digit sequence,
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* with allowance for continuation of these paths through blobs where such
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* a character does not appear in the choices list.
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*
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* GetNextParentVSE enforces some of these models to minimize the number of
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* calls to AddViterbiStateEntry, even prior to looking at the language model.
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* Thus an n-blob sequence of [l1I] will produce 3n calls to
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* AddViterbiStateEntry instead of 3^n.
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*
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* Of course it isn't quite that simple as Title Case is handled by allowing
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* lower case to continue an upper case initial, but it has to be detected
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* in the combiner so it knows which upper case letters are initial alphas.
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*/
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bool LanguageModel::UpdateState(
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bool just_classified,
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int curr_col, int curr_row,
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@ -367,10 +376,12 @@ bool LanguageModel::UpdateState(
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return new_changed;
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}
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// Finds the first lower and upper case letter and first digit in curr_list.
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// For non-upper/lower languages, alpha counts as upper.
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// Uses the first character in the list in place of empty results.
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// Returns true if both alpha and digits are found.
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/**
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* Finds the first lower and upper case letter and first digit in curr_list.
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* For non-upper/lower languages, alpha counts as upper.
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* Uses the first character in the list in place of empty results.
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* Returns true if both alpha and digits are found.
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*/
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bool LanguageModel::GetTopLowerUpperDigit(BLOB_CHOICE_LIST *curr_list,
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BLOB_CHOICE **first_lower,
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BLOB_CHOICE **first_upper,
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@ -402,13 +413,15 @@ bool LanguageModel::GetTopLowerUpperDigit(BLOB_CHOICE_LIST *curr_list,
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return mixed;
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}
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// Forces there to be at least one entry in the overall set of the
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// viterbi_state_entries of each element of parent_node that has the
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// top_choice_flag set for lower, upper and digit using the same rules as
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// GetTopLowerUpperDigit, setting the flag on the first found suitable
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// candidate, whether or not the flag is set on some other parent.
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// Returns 1 if both alpha and digits are found among the parents, -1 if no
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// parents are found at all (a legitimate case), and 0 otherwise.
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/**
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* Forces there to be at least one entry in the overall set of the
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* viterbi_state_entries of each element of parent_node that has the
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* top_choice_flag set for lower, upper and digit using the same rules as
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* GetTopLowerUpperDigit, setting the flag on the first found suitable
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* candidate, whether or not the flag is set on some other parent.
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* Returns 1 if both alpha and digits are found among the parents, -1 if no
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* parents are found at all (a legitimate case), and 0 otherwise.
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*/
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int LanguageModel::SetTopParentLowerUpperDigit(
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LanguageModelState *parent_node) const {
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if (parent_node == NULL) return -1;
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@ -481,9 +494,11 @@ int LanguageModel::SetTopParentLowerUpperDigit(
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return mixed ? 1 : 0;
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}
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// Finds the next ViterbiStateEntry with which the given unichar_id can
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// combine sensibly, taking into account any mixed alnum/mixed case
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// situation, and whether this combination has been inspected before.
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/**
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* Finds the next ViterbiStateEntry with which the given unichar_id can
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* combine sensibly, taking into account any mixed alnum/mixed case
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* situation, and whether this combination has been inspected before.
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*/
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ViterbiStateEntry* LanguageModel::GetNextParentVSE(
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bool just_classified, bool mixed_alnum, const BLOB_CHOICE* bc,
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LanguageModelFlagsType blob_choice_flags, const UNICHARSET& unicharset,
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