/* -*- c-basic-offset: 4; indent-tabs-mode: nil -*- */ /* ==================================================================== * Copyright (c) 2008 Carnegie Mellon University. All rights * reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * This work was supported in part by funding from the Defense Advanced * Research Projects Agency and the National Science Foundation of the * United States of America, and the CMU Sphinx Speech Consortium. * * THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS'' AND * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY * NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * ==================================================================== * */ /** * @file ngram_search.h N-Gram based multi-pass search ("FBS") */ #ifndef __NGRAM_SEARCH_H__ #define __NGRAM_SEARCH_H__ /* SphinxBase headers. */ #include #include #include #include #include /* Local headers. */ #include "pocketsphinx_internal.h" #include "hmm.h" /** * Lexical tree node data type. * * Not the first HMM for words, which multiplex HMMs based on * different left contexts. This structure is used both in the * dynamic HMM tree structure and in the per-word last-phone right * context fanout. */ typedef struct chan_s { hmm_t hmm; /**< Basic HMM structure. This *must* be first in the structure because chan_t and root_chan_t are sometimes used interchangeably */ struct chan_s *next; /**< first descendant of this channel; or, in the case of the last phone of a word, the next alternative right context channel */ struct chan_s *alt; /**< sibling; i.e., next descendant of parent HMM */ int32 ciphone; /**< ciphone for this node */ union { int32 penult_phn_wid; /**< list of words whose last phone follows this one; this field indicates the first of the list; the rest must be built up in a separate array. Used only within HMM tree. -1 if none */ int32 rc_id; /**< right-context id for last phone of words */ } info; } chan_t; /** * Lexical tree node data type for the first phone (root) of each dynamic HMM tree * structure. * * Each state may have a different parent static HMM. Most fields are * similar to those in chan_t. */ typedef struct root_chan_s { hmm_t hmm; /**< Basic HMM structure. This *must* be first in the structure because chan_t and root_chan_t are sometimes used interchangeably. */ chan_t *next; /**< first descendant of this channel */ int32 penult_phn_wid; int32 this_phn_wid; /**< list of words consisting of this single phone; actually the first of the list, like penult_phn_wid; -1 if none */ int16 ciphone; /**< first ciphone of this node; all words rooted at this node begin with this ciphone */ int16 ci2phone; /**< second ciphone of this node; one root HMM for each unique right context */ } root_chan_t; /** * Back pointer table (forward pass lattice; actually a tree) */ typedef struct bptbl_s { frame_idx_t frame; /**< start or end frame */ uint8 valid; /**< For absolute pruning */ uint8 refcnt; /**< Reference count (number of successors) */ int32 wid; /**< Word index */ int32 bp; /**< Back Pointer */ int32 score; /**< Score (best among all right contexts) */ int32 s_idx; /**< Start of BScoreStack for various right contexts*/ int32 real_wid; /**< wid of this or latest predecessor real word */ int32 prev_real_wid; /**< wid of second-last real word */ int16 last_phone; /**< last phone of this word */ int16 last2_phone; /**< next-to-last phone of this word */ } bptbl_t; /** * Segmentation "iterator" for backpointer table results. */ typedef struct bptbl_seg_s { ps_seg_t base; /**< Base structure. */ int32 *bpidx; /**< Sequence of backpointer IDs. */ int16 n_bpidx; /**< Number of backpointer IDs. */ int16 cur; /**< Current position in bpidx. */ } bptbl_seg_t; /* * Candidates words for entering their last phones. Cleared and rebuilt in each * frame. * NOTE: candidates can only be multi-phone, real dictionary words. */ typedef struct lastphn_cand_s { int32 wid; int32 score; int32 bp; int32 next; /* next candidate starting at the same frame */ } lastphn_cand_t; /* * Since the same instance of a word (i.e., ) reaches its last * phone several times, we can compute its best BP and LM transition score info * just the first time and cache it for future occurrences. Structure for such * a cache. */ typedef struct { int32 sf; /* Start frame */ int32 dscr; /* Delta-score upon entering last phone */ int32 bp; /* Best BP */ } last_ltrans_t; #define CAND_SF_ALLOCSIZE 32 typedef struct { int32 bp_ef; int32 cand; } cand_sf_t; /* * Structure for reorganizing the BP table entries in the current frame according * to distinct right context ci-phones. Each entry contains the best BP entry for * a given right context. Each successor word will pick up the correct entry based * on its first ci-phone. */ typedef struct bestbp_rc_s { int32 score; int32 path; /* BP table index corresponding to this entry */ int32 lc; /* right most ci-phone of above BP entry word */ } bestbp_rc_t; #define NO_BP -1 /** * Various statistics for profiling. */ typedef struct ngram_search_stats_s { int32 n_phone_eval; int32 n_root_chan_eval; int32 n_nonroot_chan_eval; int32 n_last_chan_eval; int32 n_word_lastchan_eval; int32 n_lastphn_cand_utt; int32 n_fwdflat_chan; int32 n_fwdflat_words; int32 n_fwdflat_word_transition; int32 n_senone_active_utt; } ngram_search_stats_t; /** * N-Gram search module structure. */ struct ngram_search_s { ps_search_t base; ngram_model_t *lmset; /**< Set of language models. */ hmm_context_t *hmmctx; /**< HMM context. */ /* Flags to quickly indicate which passes are enabled. */ uint8 fwdtree; uint8 fwdflat; uint8 bestpath; /* State of procesing. */ uint8 done; /* Allocators */ listelem_alloc_t *chan_alloc; /**< For chan_t */ listelem_alloc_t *root_chan_alloc; /**< For root_chan_t */ listelem_alloc_t *latnode_alloc; /**< For latnode_t */ /** * Search structure of HMM instances. * * The word triphone sequences (HMM instances) are transformed * into tree structures, one tree per unique left triphone in the * entire dictionary (actually diphone, since its left context * varies dyamically during the search process). The entire set * of trees of channels is allocated once and for all during * initialization (since dynamic management of active CHANs is * time consuming), with one exception: the last phones of words, * that need multiple right context modelling, are not maintained * in this static structure since there are too many of them and * few are active at any time. Instead they are maintained as * linked lists of CHANs, one list per word, and each CHAN in this * set is allocated only on demand and freed if inactive. */ root_chan_t *root_chan; /**< Roots of search tree. */ int32 n_root_chan_alloc; /**< Number of root_chan allocated */ int32 n_root_chan; /**< Number of valid root_chan */ int32 n_nonroot_chan; /**< Number of valid non-root channels */ int32 max_nonroot_chan; /**< Maximum possible number of non-root channels */ root_chan_t *rhmm_1ph; /**< Root HMMs for single-phone words */ /** * Channels associated with a given word (only used for right * contexts, single-phone words in fwdtree search, and word HMMs * in fwdflat search). WARNING: For single-phone words and * fwdflat search, this actually contains pointers to root_chan_t, * which are allocated using root_chan_alloc. This is a * suboptimal state of affairs. */ chan_t **word_chan; bitvec_t *word_active; /**< array of active flags for all words. */ /** * Each node in the HMM tree structure may point to a set of words * whose last phone would follow that node in the tree structure * (but is not included in the tree structure for reasons * explained above). The channel node points to one word in this * set of words. The remaining words are linked through * homophone_set[]. * * Single-phone words are not represented in the HMM tree; they * are kept in word_chan. * * Specifically, homophone_set[w] = wid of next word in the same * set as w. */ int32 *homophone_set; int32 *single_phone_wid; /**< list of single-phone word ids */ int32 n_1ph_words; /**< Number single phone words in dict (total) */ int32 n_1ph_LMwords; /**< Number single phone dict words also in LM; these come first in single_phone_wid */ /** * Array of active channels for current and next frame. * * In any frame, only some HMM tree nodes are active. * active_chan_list[f mod 2] = list of nonroot channels in the HMM * tree active in frame f. */ chan_t ***active_chan_list; int32 n_active_chan[2]; /**< Number entries in active_chan_list */ /** * Array of active multi-phone words for current and next frame. * * Similarly to active_chan_list, active_word_list[f mod 2] = list * of word ids for which active channels exist in word_chan in * frame f. * * Statically allocated single-phone words are always active and * should not appear in this list. */ int32 **active_word_list; int32 n_active_word[2]; /**< Number entries in active_word_list */ /* * FIXME: Document all of these bits. */ lastphn_cand_t *lastphn_cand; int32 n_lastphn_cand; last_ltrans_t *last_ltrans; /* one per word */ int32 cand_sf_alloc; cand_sf_t *cand_sf; bestbp_rc_t *bestbp_rc; bptbl_t *bp_table; /* Forward pass lattice */ int32 bpidx; /* First free BPTable entry */ int32 bp_table_size; int32 *bscore_stack; /* Score stack for all possible right contexts */ int32 bss_head; /* First free BScoreStack entry */ int32 bscore_stack_size; int32 n_frame_alloc; /**< Number of frames allocated in bp_table_idx and friends. */ int32 n_frame; /**< Number of frames actually present. */ int32 *bp_table_idx; /* First BPTable entry for each frame */ int32 *word_lat_idx; /* BPTable index for any word in current frame; cleared before each frame */ /* * Flat lexicon (2nd pass) search stuff. */ ps_latnode_t **frm_wordlist; /**< List of active words in each frame. */ int32 *fwdflat_wordlist; /**< List of active word IDs for utterance. */ bitvec_t *expand_word_flag; int32 *expand_word_list; int32 n_expand_words; int32 min_ef_width; int32 max_sf_win; float32 fwdflat_fwdtree_lw_ratio; int32 best_score; /**< Best Viterbi path score. */ int32 last_phone_best_score; /**< Best Viterbi path score for last phone. */ int32 renormalized; /* * DAG (3rd pass) search stuff. */ float32 bestpath_fwdtree_lw_ratio; float32 ascale; /**< Acoustic score scale for posterior probabilities. */ ngram_search_stats_t st; /**< Various statistics for profiling. */ ptmr_t fwdtree_perf; ptmr_t fwdflat_perf; ptmr_t bestpath_perf; int32 n_tot_frame; /* A collection of beam widths. */ int32 beam; int32 dynamic_beam; int32 pbeam; int32 wbeam; int32 lpbeam; int32 lponlybeam; int32 fwdflatbeam; int32 fwdflatwbeam; int32 fillpen; int32 silpen; int32 wip; int32 nwpen; int32 pip; int32 maxwpf; int32 maxhmmpf; }; typedef struct ngram_search_s ngram_search_t; /** * Initialize the N-Gram search module. */ ps_search_t *ngram_search_init(ngram_model_t *lm, cmd_ln_t *config, acmod_t *acmod, dict_t *dict, dict2pid_t *d2p); /** * Finalize the N-Gram search module. */ void ngram_search_free(ps_search_t *ngs); /** * Record the current frame's index in the backpointer table. * * @return the current backpointer index. */ int ngram_search_mark_bptable(ngram_search_t *ngs, int frame_idx); /** * Enter a word in the backpointer table. */ void ngram_search_save_bp(ngram_search_t *ngs, int frame_idx, int32 w, int32 score, int32 path, int32 rc); /** * Allocate last phone channels for all possible right contexts for word w. */ void ngram_search_alloc_all_rc(ngram_search_t *ngs, int32 w); /** * Allocate last phone channels for all possible right contexts for word w. */ void ngram_search_free_all_rc(ngram_search_t *ngs, int32 w); /** * Find the best word exit for the current frame in the backpointer table. * * @return the backpointer index of the best word exit. */ int ngram_search_find_exit(ngram_search_t *ngs, int frame_idx, int32 *out_best_score, int32 *out_is_final); /** * Backtrace from a given backpointer index to obtain a word hypothesis. * * @return a read-only string with the best hypothesis. */ char const *ngram_search_bp_hyp(ngram_search_t *ngs, int bpidx); /** * Compute language and acoustic scores for backpointer table entries. */ void ngram_compute_seg_scores(ngram_search_t *ngs, float32 lwf); /** * Construct a word lattice from the current hypothesis. */ ps_lattice_t *ngram_search_lattice(ps_search_t *search); /** * Get the exit score for a backpointer entry with a given right context. */ int32 ngram_search_exit_score(ngram_search_t *ngs, bptbl_t *pbe, int rcphone); /** * Sets the global language model. * * Sets the language model to use if nothing was passed in configuration */ void ngram_search_set_lm(ngram_model_t *lm); #endif /* __NGRAM_SEARCH_H__ */