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/*
 * fsg_history.h -- FSG Viterbi decode history
 * 
 * **********************************************
 * CMU ARPA Speech Project
 *
 * Copyright (c) 1999 Carnegie Mellon University.
 * ALL RIGHTS RESERVED.
 * **********************************************
 * 
 * HISTORY
 * 
 * $Log: fsg_history.h,v $
 * Revision 1.1.1.1  2006/05/23 18:45:02  dhuggins
 * re-importation
 *
 * Revision 1.1  2004/07/16 00:57:12  egouvea
 * Added Ravi's implementation of FSG support.
 *
 * Revision 1.7  2004/07/07 22:30:35  rkm
 * *** empty log message ***
 *
 * Revision 1.6  2004/07/07 13:56:33  rkm
 * Added reporting of (acoustic score - best senone score)/frame
 *
 * Revision 1.5  2004/06/25 14:49:08  rkm
 * Optimized size of history table and speed of word transitions by maintaining only best scoring word exits at each state
 *
 * Revision 1.4  2004/06/23 20:32:16  rkm
 * *** empty log message ***
 *
 * Revision 1.3  2004/05/27 15:16:08  rkm
 * *** empty log message ***
 *
 * 
 * 25-Feb-2004	M K Ravishankar (rkm@cs.cmu.edu) at Carnegie Mellon University
 * 		Started, based on S3.3 version.
 */


#ifndef __S2_FSG_HISTORY_H__
#define __S2_FSG_HISTORY_H__


/* SphinxBase headers. */
#include <sphinxbase/prim_type.h>
#include <sphinxbase/fsg_model.h>

/* Local headers. */
#include "blkarray_list.h"
#include "fsg_lextree.h"
#include "dict.h"

/*
 * The Viterbi history structure.  This is a tree, with the root at the
 * FSG start state, at frame 0, with a null predecessor.
 */

/*
 * A single Viterbi history entry
 */
typedef struct fsg_hist_entry_s {
    fsg_link_t *fsglink;		/* Link taken result in this entry */
    int32 score;			/* Total path score at the end of this
                                           transition */
    int32 pred; 			/* Predecessor entry; -1 if none */
    int16 frame;			/* Ending frame for this entry */
    int16 lc;			        /* Left context provided by this entry to
				           succeeding words */
    fsg_pnode_ctxt_t rc;		/* Possible right contexts to which this entry
                                           applies */
} fsg_hist_entry_t;

/* Access macros */
#define fsg_hist_entry_fsglink(v)	((v)->fsglink)
#define fsg_hist_entry_frame(v)		((v)->frame)
#define fsg_hist_entry_score(v)		((v)->score)
#define fsg_hist_entry_pred(v)		((v)->pred)
#define fsg_hist_entry_lc(v)		((v)->lc)
#define fsg_hist_entry_rc(v)		((v)->rc)


/*
 * The entire tree of history entries (fsg_history_t.entries).
 * Optimization: In a given frame, there may be several history entries, with
 * the same left and right phonetic context, terminating in a particular state.
 * Only the best scoring one of these needs to be saved, since everything else
 * will be pruned according to the Viterbi algorithm.  frame_entries is used
 * temporarily in each frame to determine these best scoring entries in that
 * frame.  Only the ones not pruned are transferred to entries at the end of
 * the frame.  However, null transitions are a problem since they create
 * entries that depend on entries created in the CURRENT frame.  Hence, this
 * pruning is done in two stages: first for the non-null transitions, and then
 * for the null transitions alone.  (This solution is sub-optimal, and can be
 * improved with a little more work.  SMOP.)
 * Why is frame_entries a list?  Each entry has a unique terminating state,
 * and has a unique lc CIphone.  But it has a SET of rc CIphones.
 * frame_entries[s][lc] is an ordered list of entries created in the current
 * frame, terminating in state s, and with left context lc.  The list is in
 * descending order of path score.  When a new entry with (s,lc) arrives,
 * its position in the list is determined.  Then its rc set is modified by
 * subtracting the union of the rc's of all its predecessors (i.e., better
 * scoring entries).  If the resulting rc set is empty, the entry is discarded.
 * Otherwise, it is inserted, and the rc sets of all downstream entries in the
 * list are updated by subtracting the new entry's rc.  If any of them becomes
 * empty, it is also discarded.
 * As mentioned earlier, this procedure is applied in two stages, for the
 * non-null transitions, and the null transitions, separately.
 */
typedef struct fsg_history_s {
    fsg_model_t *fsg;		/* The FSG for which this object applies */
    blkarray_list_t *entries;	/* A list of history table entries; the root
				   entry is the first element of the list */
    glist_t **frame_entries;
    int n_ciphone;
} fsg_history_t;


/*
 * One-time intialization: Allocate and return an initially empty history
 * module.
 */
fsg_history_t *fsg_history_init(fsg_model_t *fsg, dict_t *dict);

void fsg_history_utt_start(fsg_history_t *h);

void fsg_history_utt_end(fsg_history_t *h);


/*
 * Create a history entry recording the completion of the given FSG
 * transition, at the end of the given frame, with the given score, and
 * the given predecessor history entry.
 * The entry is initially temporary, and may be superseded by another
 * with a higher score.  The surviving entries must be transferred to
 * the main history table, via fsg_history_end_frame().
 */
void fsg_history_entry_add (fsg_history_t *h,
			    fsg_link_t *l,	/* FSG transition */
			    int32 frame,
			    int32 score,
			    int32 pred,
			    int32 lc,
			    fsg_pnode_ctxt_t rc);

/*
 * Transfer the surviving history entries for this frame into the permanent
 * history table.  This function can be called several times during a frame.
 * Each time, the entries surviving so far are transferred, and the temporary
 * lists cleared.  This feature is used to handle the entries due to non-null
 * transitions and null transitions separately.
 */
void fsg_history_end_frame (fsg_history_t *h);


/* Clear the hitory table */
void fsg_history_reset (fsg_history_t *h);


/* Return the number of valid entries in the given history table */
int32 fsg_history_n_entries (fsg_history_t *h);

/*
 * Return a ptr to the history entry for the given ID; NULL if there is no
 * such entry.
 */
fsg_hist_entry_t *fsg_history_entry_get(fsg_history_t *h, int32 id);


/*
 * Switch the FSG associated with the given history module.  Should be done
 * when the history list is empty.  If not empty, the list is cleared.
 */
void fsg_history_set_fsg (fsg_history_t *h, fsg_model_t *fsg, dict_t *dict);

/* Free the given Viterbi search history object */
void fsg_history_free (fsg_history_t *h);
				     
#endif
