Add m-esr52 at 52.6.0

1 files changed, 1550 insertions, 0 deletions

diff --git a/media/pocketsphinx/src/fsg_search.c b/media/pocketsphinx/src/fsg_search.c
new file mode 100644
index 000000000..f24a0fb83
--- /dev/null
+++ b/media/pocketsphinx/src/fsg_search.c
@@ -0,0 +1,1550 @@
+/* -*- c-basic-offset: 4; indent-tabs-mode: nil -*- */
+/* ====================================================================
+ * Copyright (c) 1999-2004 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 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.
+ *
+ * ====================================================================
+ *
+ */
+
+/*
+ * fsg_search.c -- Search structures for FSM decoding.
+ * 
+ * **********************************************
+ * CMU ARPA Speech Project
+ *
+ * Copyright (c) 2004 Carnegie Mellon University.
+ * ALL RIGHTS RESERVED.
+ * **********************************************
+ * 
+ * HISTORY
+ *
+ * 18-Feb-2004	M K Ravishankar (rkm@cs.cmu.edu) at Carnegie Mellon
+ * 		Started.
+ */
+
+/* System headers. */
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+/* SphinxBase headers. */
+#include <sphinxbase/err.h>
+#include <sphinxbase/ckd_alloc.h>
+#include <sphinxbase/strfuncs.h>
+#include <sphinxbase/cmd_ln.h>
+
+/* Local headers. */
+#include "pocketsphinx_internal.h"
+#include "ps_lattice_internal.h"
+#include "fsg_search_internal.h"
+#include "fsg_history.h"
+#include "fsg_lextree.h"
+#include "dict.h"
+
+/* Turn this on for detailed debugging dump */
+#define __FSG_DBG__		0
+#define __FSG_DBG_CHAN__	0
+
+static ps_seg_t *fsg_search_seg_iter(ps_search_t *search, int32 *out_score);
+static ps_lattice_t *fsg_search_lattice(ps_search_t *search);
+static int fsg_search_prob(ps_search_t *search);
+
+static ps_searchfuncs_t fsg_funcs = {
+    /* name: */   "fsg",
+    /* start: */  fsg_search_start,
+    /* step: */   fsg_search_step,
+    /* finish: */ fsg_search_finish,
+    /* reinit: */ fsg_search_reinit,
+    /* free: */   fsg_search_free,
+    /* lattice: */  fsg_search_lattice,
+    /* hyp: */      fsg_search_hyp,
+    /* prob: */     fsg_search_prob,
+    /* seg_iter: */ fsg_search_seg_iter,
+};
+
+static int
+fsg_search_add_silences(fsg_search_t *fsgs, fsg_model_t *fsg)
+{
+    dict_t *dict;
+    int32 wid;
+    int n_sil;
+
+    dict = ps_search_dict(fsgs);
+    /*
+     * NOTE: Unlike N-Gram search, we do not use explicit start and
+     * end symbols.  This is because the start and end nodes are
+     * defined in the grammar.  We do add silence/filler self-loops to
+     * all states in order to allow for silence between words and at
+     * the beginning and end of utterances.
+     *
+     * This has some implications for word graph generation, namely,
+     * that there can (and usually will) be multiple start and end
+     * states in the word graph.  We therefore do add explicit start
+     * and end nodes to the graph.
+     */
+    /* Add silence self-loops to all states. */
+    fsg_model_add_silence(fsg, "<sil>", -1,
+                          cmd_ln_float32_r(ps_search_config(fsgs), "-silprob"));
+    n_sil = 0;
+    /* Add self-loops for all other fillers. */
+    for (wid = dict_filler_start(dict); wid < dict_filler_end(dict); ++wid) {
+        char const *word = dict_wordstr(dict, wid);
+        if (wid == dict_startwid(dict) || wid == dict_finishwid(dict))
+            continue;
+        fsg_model_add_silence(fsg, word, -1,
+                              cmd_ln_float32_r(ps_search_config(fsgs), "-fillprob"));
+        ++n_sil;
+    }
+
+    return n_sil;
+}
+
+/* Scans the dictionary and check if all words are present. */
+static int
+fsg_search_check_dict(fsg_search_t *fsgs, fsg_model_t *fsg)
+{
+    dict_t *dict;
+    int i;
+
+    dict = ps_search_dict(fsgs);
+    for (i = 0; i < fsg_model_n_word(fsg); ++i) {
+        char const *word;
+        int32 wid;
+
+        word = fsg_model_word_str(fsg, i);
+        wid = dict_wordid(dict, word);
+        if (wid == BAD_S3WID) {
+            E_WARN("The word '%s' is missing in the dictionary. Trying to create new phoneme \n", word);
+            if (!dict->ngram_g2p_model) {
+                E_ERROR("NO dict->ngram_g2p_model. Aborting..");
+                return FALSE;
+            }
+
+            int new_wid = dict_add_g2p_word(dict, word);
+            if (new_wid > 0){
+                /* Now we also have to add it to dict2pid. */
+                dict2pid_add_word(ps_search_dict2pid(fsgs), new_wid);
+            } else {
+                E_ERROR("Exiting... \n");
+                return FALSE;
+            }
+        }
+    }
+
+    return TRUE;
+}
+
+static int
+fsg_search_add_altpron(fsg_search_t *fsgs, fsg_model_t *fsg)
+{
+    dict_t *dict;
+    int n_alt, n_word;
+    int i;
+
+    dict = ps_search_dict(fsgs);
+    /* Scan FSG's vocabulary for words that have alternate pronunciations. */
+    n_alt = 0;
+    n_word = fsg_model_n_word(fsg);
+    for (i = 0; i < n_word; ++i) {
+        char const *word;
+        int32 wid;
+
+        word = fsg_model_word_str(fsg, i);
+        wid = dict_wordid(dict, word);
+        if (wid != BAD_S3WID) {
+            while ((wid = dict_nextalt(dict, wid)) != BAD_S3WID) {
+	        n_alt += fsg_model_add_alt(fsg, word, dict_wordstr(dict, wid));
+    	    }
+    	}
+    }
+
+    E_INFO("Added %d alternate word transitions\n", n_alt);
+    return n_alt;
+}
+
+ps_search_t *
+fsg_search_init(fsg_model_t *fsg,
+                cmd_ln_t *config,
+                acmod_t *acmod,
+                dict_t *dict,
+                dict2pid_t *d2p)
+{
+    fsg_search_t *fsgs = ckd_calloc(1, sizeof(*fsgs));
+    ps_search_init(ps_search_base(fsgs), &fsg_funcs, config, acmod, dict, d2p);
+
+    fsgs->fsg = fsg_model_retain(fsg);
+    /* Initialize HMM context. */
+    fsgs->hmmctx = hmm_context_init(bin_mdef_n_emit_state(acmod->mdef),
+                                    acmod->tmat->tp, NULL, acmod->mdef->sseq);
+    if (fsgs->hmmctx == NULL) {
+        ps_search_free(ps_search_base(fsgs));
+        return NULL;
+    }
+
+    /* Intialize the search history object */
+    fsgs->history = fsg_history_init(NULL, dict);
+    fsgs->frame = -1;
+
+    /* Get search pruning parameters */
+    fsgs->beam_factor = 1.0f;
+    fsgs->beam = fsgs->beam_orig
+        = (int32) logmath_log(acmod->lmath, cmd_ln_float64_r(config, "-beam"))
+        >> SENSCR_SHIFT;
+    fsgs->pbeam = fsgs->pbeam_orig
+        = (int32) logmath_log(acmod->lmath, cmd_ln_float64_r(config, "-pbeam"))
+        >> SENSCR_SHIFT;
+    fsgs->wbeam = fsgs->wbeam_orig
+        = (int32) logmath_log(acmod->lmath, cmd_ln_float64_r(config, "-wbeam"))
+        >> SENSCR_SHIFT;
+
+    /* LM related weights/penalties */
+    fsgs->lw = cmd_ln_float32_r(config, "-lw");
+    fsgs->pip = (int32) (logmath_log(acmod->lmath, cmd_ln_float32_r(config, "-pip"))
+                           * fsgs->lw)
+        >> SENSCR_SHIFT;
+    fsgs->wip = (int32) (logmath_log(acmod->lmath, cmd_ln_float32_r(config, "-wip"))
+                           * fsgs->lw)
+        >> SENSCR_SHIFT;
+
+    /* Acoustic score scale for posterior probabilities. */
+    fsgs->ascale = 1.0 / cmd_ln_float32_r(config, "-ascale");
+
+    E_INFO("FSG(beam: %d, pbeam: %d, wbeam: %d; wip: %d, pip: %d)\n",
+           fsgs->beam_orig, fsgs->pbeam_orig, fsgs->wbeam_orig,
+           fsgs->wip, fsgs->pip);
+
+    if (!fsg_search_check_dict(fsgs, fsg)) {
+        fsg_search_free(ps_search_base(fsgs));
+        return NULL;
+    }
+
+    if (cmd_ln_boolean_r(config, "-fsgusefiller") &&
+        !fsg_model_has_sil(fsg))
+        fsg_search_add_silences(fsgs, fsg);
+
+    if (cmd_ln_boolean_r(config, "-fsgusealtpron") &&
+        !fsg_model_has_alt(fsg))
+        fsg_search_add_altpron(fsgs, fsg);
+
+    if (fsg_search_reinit(ps_search_base(fsgs),
+                          ps_search_dict(fsgs),
+                          ps_search_dict2pid(fsgs)) < 0)
+    {
+        ps_search_free(ps_search_base(fsgs));
+        return NULL;
+    }
+        
+    return ps_search_base(fsgs);
+}
+
+void
+fsg_search_free(ps_search_t *search)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+
+    ps_search_deinit(search);
+    fsg_lextree_free(fsgs->lextree);
+    if (fsgs->history) {
+        fsg_history_reset(fsgs->history);
+        fsg_history_set_fsg(fsgs->history, NULL, NULL);
+        fsg_history_free(fsgs->history);
+    }
+    hmm_context_free(fsgs->hmmctx);
+    fsg_model_free(fsgs->fsg);
+    ckd_free(fsgs);
+}
+
+int
+fsg_search_reinit(ps_search_t *search, dict_t *dict, dict2pid_t *d2p)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+
+    /* Free the old lextree */
+    if (fsgs->lextree)
+        fsg_lextree_free(fsgs->lextree);
+
+    /* Free old dict2pid, dict */
+    ps_search_base_reinit(search, dict, d2p);
+    
+    /* Update the number of words (not used by this module though). */
+    search->n_words = dict_size(dict);
+
+    /* Allocate new lextree for the given FSG */
+    fsgs->lextree = fsg_lextree_init(fsgs->fsg, dict, d2p,
+                                     ps_search_acmod(fsgs)->mdef,
+                                     fsgs->hmmctx, fsgs->wip, fsgs->pip);
+
+    /* Inform the history module of the new fsg */
+    fsg_history_set_fsg(fsgs->history, fsgs->fsg, dict);
+
+    return 0;
+}
+
+
+static void
+fsg_search_sen_active(fsg_search_t *fsgs)
+{
+    gnode_t *gn;
+    fsg_pnode_t *pnode;
+    hmm_t *hmm;
+
+    acmod_clear_active(ps_search_acmod(fsgs));
+
+    for (gn = fsgs->pnode_active; gn; gn = gnode_next(gn)) {
+        pnode = (fsg_pnode_t *) gnode_ptr(gn);
+        hmm = fsg_pnode_hmmptr(pnode);
+        assert(hmm_frame(hmm) == fsgs->frame);
+        acmod_activate_hmm(ps_search_acmod(fsgs), hmm);
+    }
+}
+
+
+/*
+ * Evaluate all the active HMMs.
+ * (Executed once per frame.)
+ */
+static void
+fsg_search_hmm_eval(fsg_search_t *fsgs)
+{
+    gnode_t *gn;
+    fsg_pnode_t *pnode;
+    hmm_t *hmm;
+    int32 bestscore;
+    int32 n, maxhmmpf;
+
+    bestscore = WORST_SCORE;
+
+    if (!fsgs->pnode_active) {
+        E_ERROR("Frame %d: No active HMM!!\n", fsgs->frame);
+        return;
+    }
+
+    for (n = 0, gn = fsgs->pnode_active; gn; gn = gnode_next(gn), n++) {
+        int32 score;
+
+        pnode = (fsg_pnode_t *) gnode_ptr(gn);
+        hmm = fsg_pnode_hmmptr(pnode);
+        assert(hmm_frame(hmm) == fsgs->frame);
+
+#if __FSG_DBG__
+        E_INFO("pnode(%08x) active @frm %5d\n", (int32) pnode,
+               fsgs->frame);
+        hmm_dump(hmm, stdout);
+#endif
+        score = hmm_vit_eval(hmm);
+#if __FSG_DBG_CHAN__
+        E_INFO("pnode(%08x) after eval @frm %5d\n",
+               (int32) pnode, fsgs->frame);
+        hmm_dump(hmm, stdout);
+#endif
+
+        if (score BETTER_THAN bestscore)
+            bestscore = score;
+    }
+
+#if __FSG_DBG__
+    E_INFO("[%5d] %6d HMM; bestscr: %11d\n", fsgs->frame, n, bestscore);
+#endif
+    fsgs->n_hmm_eval += n;
+
+    /* Adjust beams if #active HMMs larger than absolute threshold */
+    maxhmmpf = cmd_ln_int32_r(ps_search_config(fsgs), "-maxhmmpf");
+    if (maxhmmpf != -1 && n > maxhmmpf) {
+        /*
+         * Too many HMMs active; reduce the beam factor applied to the default
+         * beams, but not if the factor is already at a floor (0.1).
+         */
+        if (fsgs->beam_factor > 0.1) {        /* Hack!!  Hardwired constant 0.1 */
+            fsgs->beam_factor *= 0.9f;        /* Hack!!  Hardwired constant 0.9 */
+            fsgs->beam =
+                (int32) (fsgs->beam_orig * fsgs->beam_factor);
+            fsgs->pbeam =
+                (int32) (fsgs->pbeam_orig * fsgs->beam_factor);
+            fsgs->wbeam =
+                (int32) (fsgs->wbeam_orig * fsgs->beam_factor);
+        }
+    }
+    else {
+        fsgs->beam_factor = 1.0f;
+        fsgs->beam = fsgs->beam_orig;
+        fsgs->pbeam = fsgs->pbeam_orig;
+        fsgs->wbeam = fsgs->wbeam_orig;
+    }
+
+    if (n > fsg_lextree_n_pnode(fsgs->lextree))
+        E_FATAL("PANIC! Frame %d: #HMM evaluated(%d) > #PNodes(%d)\n",
+                fsgs->frame, n, fsg_lextree_n_pnode(fsgs->lextree));
+
+    fsgs->bestscore = bestscore;
+}
+
+
+static void
+fsg_search_pnode_trans(fsg_search_t *fsgs, fsg_pnode_t * pnode)
+{
+    fsg_pnode_t *child;
+    hmm_t *hmm;
+    int32 newscore, thresh, nf;
+
+    assert(pnode);
+    assert(!fsg_pnode_leaf(pnode));
+
+    nf = fsgs->frame + 1;
+    thresh = fsgs->bestscore + fsgs->beam;
+
+    hmm = fsg_pnode_hmmptr(pnode);
+
+    for (child = fsg_pnode_succ(pnode);
+         child; child = fsg_pnode_sibling(child)) {
+        newscore = hmm_out_score(hmm) + child->logs2prob;
+
+        if ((newscore BETTER_THAN thresh)
+            && (newscore BETTER_THAN hmm_in_score(&child->hmm))) {
+            /* Incoming score > pruning threshold and > target's existing score */
+            if (hmm_frame(&child->hmm) < nf) {
+                /* Child node not yet activated; do so */
+                fsgs->pnode_active_next =
+                    glist_add_ptr(fsgs->pnode_active_next,
+                                  (void *) child);
+            }
+
+            hmm_enter(&child->hmm, newscore, hmm_out_history(hmm), nf);
+        }
+    }
+}
+
+
+static void
+fsg_search_pnode_exit(fsg_search_t *fsgs, fsg_pnode_t * pnode)
+{
+    hmm_t *hmm;
+    fsg_link_t *fl;
+    int32 wid;
+    fsg_pnode_ctxt_t ctxt;
+
+    assert(pnode);
+    assert(fsg_pnode_leaf(pnode));
+
+    hmm = fsg_pnode_hmmptr(pnode);
+    fl = fsg_pnode_fsglink(pnode);
+    assert(fl);
+
+    wid = fsg_link_wid(fl);
+    assert(wid >= 0);
+
+#if __FSG_DBG__
+    E_INFO("[%5d] Exit(%08x) %10d(score) %5d(pred)\n",
+           fsgs->frame, (int32) pnode,
+           hmm_out_score(hmm), hmm_out_history(hmm));
+#endif
+
+    /*
+     * Check if this is filler or single phone word; these do not model right
+     * context (i.e., the exit score applies to all right contexts).
+     */
+    if (fsg_model_is_filler(fsgs->fsg, wid)
+        /* FIXME: This might be slow due to repeated calls to dict_to_id(). */
+        || (dict_is_single_phone(ps_search_dict(fsgs),
+                                   dict_wordid(ps_search_dict(fsgs),
+                                               fsg_model_word_str(fsgs->fsg, wid))))) {
+        /* Create a dummy context structure that applies to all right contexts */
+        fsg_pnode_add_all_ctxt(&ctxt);
+
+        /* Create history table entry for this word exit */
+        fsg_history_entry_add(fsgs->history,
+                              fl,
+                              fsgs->frame,
+                              hmm_out_score(hmm),
+                              hmm_out_history(hmm),
+                              pnode->ci_ext, ctxt);
+
+    }
+    else {
+        /* Create history table entry for this word exit */
+        fsg_history_entry_add(fsgs->history,
+                              fl,
+                              fsgs->frame,
+                              hmm_out_score(hmm),
+                              hmm_out_history(hmm),
+                              pnode->ci_ext, pnode->ctxt);
+    }
+}
+
+
+/*
+ * (Beam) prune the just evaluated HMMs, determine which ones remain
+ * active, which ones transition to successors, which ones exit and
+ * terminate in their respective destination FSM states.
+ * (Executed once per frame.)
+ */
+static void
+fsg_search_hmm_prune_prop(fsg_search_t *fsgs)
+{
+    gnode_t *gn;
+    fsg_pnode_t *pnode;
+    hmm_t *hmm;
+    int32 thresh, word_thresh, phone_thresh;
+
+    assert(fsgs->pnode_active_next == NULL);
+
+    thresh = fsgs->bestscore + fsgs->beam;
+    phone_thresh = fsgs->bestscore + fsgs->pbeam;
+    word_thresh = fsgs->bestscore + fsgs->wbeam;
+
+    for (gn = fsgs->pnode_active; gn; gn = gnode_next(gn)) {
+        pnode = (fsg_pnode_t *) gnode_ptr(gn);
+        hmm = fsg_pnode_hmmptr(pnode);
+
+        if (hmm_bestscore(hmm) >= thresh) {
+            /* Keep this HMM active in the next frame */
+            if (hmm_frame(hmm) == fsgs->frame) {
+                hmm_frame(hmm) = fsgs->frame + 1;
+                fsgs->pnode_active_next =
+                    glist_add_ptr(fsgs->pnode_active_next,
+                                  (void *) pnode);
+            }
+            else {
+                assert(hmm_frame(hmm) == fsgs->frame + 1);
+            }
+
+            if (!fsg_pnode_leaf(pnode)) {
+                if (hmm_out_score(hmm) >= phone_thresh) {
+                    /* Transition out of this phone into its children */
+                    fsg_search_pnode_trans(fsgs, pnode);
+                }
+            }
+            else {
+                if (hmm_out_score(hmm) >= word_thresh) {
+                    /* Transition out of leaf node into destination FSG state */
+                    fsg_search_pnode_exit(fsgs, pnode);
+                }
+            }
+        }
+    }
+}
+
+
+/*
+ * Propagate newly created history entries through null transitions.
+ */
+static void
+fsg_search_null_prop(fsg_search_t *fsgs)
+{
+    int32 bpidx, n_entries, thresh, newscore;
+    fsg_hist_entry_t *hist_entry;
+    fsg_link_t *l;
+    int32 s;
+    fsg_model_t *fsg;
+
+    fsg = fsgs->fsg;
+    thresh = fsgs->bestscore + fsgs->wbeam; /* Which beam really?? */
+
+    n_entries = fsg_history_n_entries(fsgs->history);
+
+    for (bpidx = fsgs->bpidx_start; bpidx < n_entries; bpidx++) {
+        fsg_arciter_t *itor;
+        hist_entry = fsg_history_entry_get(fsgs->history, bpidx);
+
+        l = fsg_hist_entry_fsglink(hist_entry);
+
+        /* Destination FSG state for history entry */
+        s = l ? fsg_link_to_state(l) : fsg_model_start_state(fsg);
+
+        /*
+         * Check null transitions from d to all other states.  (Only need to
+         * propagate one step, since FSG contains transitive closure of null
+         * transitions.)
+         */
+        /* Add all links from from_state to dst */
+        for (itor = fsg_model_arcs(fsg, s); itor;
+             itor = fsg_arciter_next(itor)) {
+            fsg_link_t *l = fsg_arciter_get(itor);
+
+            /* FIXME: Need to deal with tag transitions somehow. */
+            if (fsg_link_wid(l) != -1)
+                continue;
+            newscore =
+                fsg_hist_entry_score(hist_entry) +
+                (fsg_link_logs2prob(l) >> SENSCR_SHIFT);
+
+            if (newscore >= thresh) {
+                fsg_history_entry_add(fsgs->history, l,
+                                      fsg_hist_entry_frame(hist_entry),
+                                      newscore,
+                                      bpidx,
+                                      fsg_hist_entry_lc(hist_entry),
+                                      fsg_hist_entry_rc(hist_entry));
+            }
+        }
+    }
+}
+
+
+/*
+ * Perform cross-word transitions; propagate each history entry created in this
+ * frame to lextree roots attached to the target FSG state for that entry.
+ */
+static void
+fsg_search_word_trans(fsg_search_t *fsgs)
+{
+    int32 bpidx, n_entries;
+    fsg_hist_entry_t *hist_entry;
+    fsg_link_t *l;
+    int32 score, newscore, thresh, nf, d;
+    fsg_pnode_t *root;
+    int32 lc, rc;
+
+    n_entries = fsg_history_n_entries(fsgs->history);
+
+    thresh = fsgs->bestscore + fsgs->beam;
+    nf = fsgs->frame + 1;
+
+    for (bpidx = fsgs->bpidx_start; bpidx < n_entries; bpidx++) {
+        hist_entry = fsg_history_entry_get(fsgs->history, bpidx);
+        assert(hist_entry);
+        score = fsg_hist_entry_score(hist_entry);
+        assert(fsgs->frame == fsg_hist_entry_frame(hist_entry));
+
+        l = fsg_hist_entry_fsglink(hist_entry);
+
+        /* Destination state for hist_entry */
+        d = l ? fsg_link_to_state(l) : fsg_model_start_state(fsgs->
+                                                                fsg);
+
+        lc = fsg_hist_entry_lc(hist_entry);
+
+        /* Transition to all root nodes attached to state d */
+        for (root = fsg_lextree_root(fsgs->lextree, d);
+             root; root = root->sibling) {
+            rc = root->ci_ext;
+
+            if ((root->ctxt.bv[lc >> 5] & (1 << (lc & 0x001f))) &&
+                (hist_entry->rc.bv[rc >> 5] & (1 << (rc & 0x001f)))) {
+                /*
+                 * Last CIphone of history entry is in left-context list supported by
+                 * target root node, and
+                 * first CIphone of target root node is in right context list supported
+                 * by history entry;
+                 * So the transition can go ahead (if new score is good enough).
+                 */
+                newscore = score + root->logs2prob;
+
+                if ((newscore BETTER_THAN thresh)
+                    && (newscore BETTER_THAN hmm_in_score(&root->hmm))) {
+                    if (hmm_frame(&root->hmm) < nf) {
+                        /* Newly activated node; add to active list */
+                        fsgs->pnode_active_next =
+                            glist_add_ptr(fsgs->pnode_active_next,
+                                          (void *) root);
+#if __FSG_DBG__
+                        E_INFO
+                            ("[%5d] WordTrans bpidx[%d] -> pnode[%08x] (activated)\n",
+                             fsgs->frame, bpidx, (int32) root);
+#endif
+                    }
+                    else {
+#if __FSG_DBG__
+                        E_INFO
+                            ("[%5d] WordTrans bpidx[%d] -> pnode[%08x]\n",
+                             fsgs->frame, bpidx, (int32) root);
+#endif
+                    }
+
+                    hmm_enter(&root->hmm, newscore, bpidx, nf);
+                }
+            }
+        }
+    }
+}
+
+
+int
+fsg_search_step(ps_search_t *search, int frame_idx)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+    int16 const *senscr;
+    acmod_t *acmod = search->acmod;
+    gnode_t *gn;
+    fsg_pnode_t *pnode;
+    hmm_t *hmm;
+
+    /* Activate our HMMs for the current frame if need be. */
+    if (!acmod->compallsen)
+        fsg_search_sen_active(fsgs);
+    /* Compute GMM scores for the current frame. */
+    senscr = acmod_score(acmod, &frame_idx);
+    fsgs->n_sen_eval += acmod->n_senone_active;
+    hmm_context_set_senscore(fsgs->hmmctx, senscr);
+
+    /* Mark backpointer table for current frame. */
+    fsgs->bpidx_start = fsg_history_n_entries(fsgs->history);
+
+    /* Evaluate all active pnodes (HMMs) */
+    fsg_search_hmm_eval(fsgs);
+
+    /*
+     * Prune and propagate the HMMs evaluated; create history entries for
+     * word exits.  The words exits are tentative, and may be pruned; make
+     * the survivors permanent via fsg_history_end_frame().
+     */
+    fsg_search_hmm_prune_prop(fsgs);
+    fsg_history_end_frame(fsgs->history);
+
+    /*
+     * Propagate new history entries through any null transitions, creating
+     * new history entries, and then make the survivors permanent.
+     */
+    fsg_search_null_prop(fsgs);
+    fsg_history_end_frame(fsgs->history);
+
+    /*
+     * Perform cross-word transitions; propagate each history entry across its
+     * terminating state to the root nodes of the lextree attached to the state.
+     */
+    fsg_search_word_trans(fsgs);
+
+    /*
+     * We've now come full circle, HMM and FSG states have been updated for
+     * the next frame.
+     * Update the active lists, deactivate any currently active HMMs that
+     * did not survive into the next frame
+     */
+    for (gn = fsgs->pnode_active; gn; gn = gnode_next(gn)) {
+        pnode = (fsg_pnode_t *) gnode_ptr(gn);
+        hmm = fsg_pnode_hmmptr(pnode);
+
+        if (hmm_frame(hmm) == fsgs->frame) {
+            /* This HMM NOT activated for the next frame; reset it */
+            fsg_psubtree_pnode_deactivate(pnode);
+        }
+        else {
+            assert(hmm_frame(hmm) == (fsgs->frame + 1));
+        }
+    }
+
+    /* Free the currently active list */
+    glist_free(fsgs->pnode_active);
+
+    /* Make the next-frame active list the current one */
+    fsgs->pnode_active = fsgs->pnode_active_next;
+    fsgs->pnode_active_next = NULL;
+
+    /* End of this frame; ready for the next */
+    ++fsgs->frame;
+
+    return 1;
+}
+
+
+/*
+ * Set all HMMs to inactive, clear active lists, initialize FSM start
+ * state to be the only active node.
+ * (Executed at the start of each utterance.)
+ */
+int
+fsg_search_start(ps_search_t *search)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+    int32 silcipid;
+    fsg_pnode_ctxt_t ctxt;
+
+    /* Reset dynamic adjustment factor for beams */
+    fsgs->beam_factor = 1.0f;
+    fsgs->beam = fsgs->beam_orig;
+    fsgs->pbeam = fsgs->pbeam_orig;
+    fsgs->wbeam = fsgs->wbeam_orig;
+
+    silcipid = bin_mdef_ciphone_id(ps_search_acmod(fsgs)->mdef, "SIL");
+
+    /* Initialize EVERYTHING to be inactive */
+    assert(fsgs->pnode_active == NULL);
+    assert(fsgs->pnode_active_next == NULL);
+
+    fsg_history_reset(fsgs->history);
+    fsg_history_utt_start(fsgs->history);
+    fsgs->final = FALSE;
+
+    /* Dummy context structure that allows all right contexts to use this entry */
+    fsg_pnode_add_all_ctxt(&ctxt);
+
+    /* Create dummy history entry leading to start state */
+    fsgs->frame = -1;
+    fsgs->bestscore = 0;
+    fsg_history_entry_add(fsgs->history,
+                          NULL, -1, 0, -1, silcipid, ctxt);
+    fsgs->bpidx_start = 0;
+
+    /* Propagate dummy history entry through NULL transitions from start state */
+    fsg_search_null_prop(fsgs);
+
+    /* Perform word transitions from this dummy history entry */
+    fsg_search_word_trans(fsgs);
+
+    /* Make the next-frame active list the current one */
+    fsgs->pnode_active = fsgs->pnode_active_next;
+    fsgs->pnode_active_next = NULL;
+
+    ++fsgs->frame;
+
+    fsgs->n_hmm_eval = 0;
+    fsgs->n_sen_eval = 0;
+
+    return 0;
+}
+
+/*
+ * Cleanup at the end of each utterance.
+ */
+int
+fsg_search_finish(ps_search_t *search)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+    gnode_t *gn;
+    fsg_pnode_t *pnode;
+    int32 n_hist;
+
+    /* Deactivate all nodes in the current and next-frame active lists */
+    for (gn = fsgs->pnode_active; gn; gn = gnode_next(gn)) {
+        pnode = (fsg_pnode_t *) gnode_ptr(gn);
+        fsg_psubtree_pnode_deactivate(pnode);
+    }
+    for (gn = fsgs->pnode_active_next; gn; gn = gnode_next(gn)) {
+        pnode = (fsg_pnode_t *) gnode_ptr(gn);
+        fsg_psubtree_pnode_deactivate(pnode);
+    }
+
+    glist_free(fsgs->pnode_active);
+    fsgs->pnode_active = NULL;
+    glist_free(fsgs->pnode_active_next);
+    fsgs->pnode_active_next = NULL;
+
+    fsgs->final = TRUE;
+
+    n_hist = fsg_history_n_entries(fsgs->history);
+    E_INFO
+        ("%d frames, %d HMMs (%d/fr), %d senones (%d/fr), %d history entries (%d/fr)\n\n",
+         fsgs->frame, fsgs->n_hmm_eval,
+         (fsgs->frame > 0) ? fsgs->n_hmm_eval / fsgs->frame : 0,
+         fsgs->n_sen_eval,
+         (fsgs->frame > 0) ? fsgs->n_sen_eval / fsgs->frame : 0,
+         n_hist, (fsgs->frame > 0) ? n_hist / fsgs->frame : 0);
+
+    return 0;
+}
+
+static int
+fsg_search_find_exit(fsg_search_t *fsgs, int frame_idx, int final, int32 *out_score, int32* out_is_final)
+{
+    fsg_hist_entry_t *hist_entry = NULL;
+    fsg_model_t *fsg;
+    int bpidx, frm, last_frm, besthist;
+    int32 bestscore;
+
+    if (out_is_final)
+	*out_is_final = FALSE;
+
+    if (frame_idx == -1)
+        frame_idx = fsgs->frame - 1;
+    last_frm = frm = frame_idx;
+
+    /* Scan backwards to find a word exit in frame_idx. */
+    bpidx = fsg_history_n_entries(fsgs->history) - 1;
+    while (bpidx > 0) {
+        hist_entry = fsg_history_entry_get(fsgs->history, bpidx);
+        if (fsg_hist_entry_frame(hist_entry) <= frame_idx) {
+            frm = last_frm = fsg_hist_entry_frame(hist_entry);
+            break;
+        }
+        bpidx--;
+    }
+
+    /* No hypothesis (yet). */
+    if (bpidx <= 0)
+        return bpidx;
+
+    /* Now find best word exit in this frame. */
+    bestscore = INT_MIN;
+    besthist = -1;
+    fsg = fsgs->fsg;
+    while (frm == last_frm) {
+        fsg_link_t *fl;
+        int32 score;
+
+        fl = fsg_hist_entry_fsglink(hist_entry);
+        score = fsg_hist_entry_score(hist_entry);
+        
+        if (fl == NULL)
+	    break;
+
+	/* Prefer final hypothesis */
+	if (score == bestscore && fsg_link_to_state(fl) == fsg_model_final_state(fsg)) {
+    	    besthist = bpidx;
+	} else if (score BETTER_THAN bestscore) {
+            /* Only enforce the final state constraint if this is a final hypothesis. */
+            if ((!final)
+                || fsg_link_to_state(fl) == fsg_model_final_state(fsg)) {
+                bestscore = score;
+                besthist = bpidx;
+            }
+        }
+        
+        --bpidx;
+        if (bpidx < 0)
+            break;
+        hist_entry = fsg_history_entry_get(fsgs->history, bpidx);
+        frm = fsg_hist_entry_frame(hist_entry);
+    }
+
+    /* Final state not reached. */
+    if (besthist == -1) {
+        E_ERROR("Final result does not match the grammar in frame %d\n", frame_idx);
+        return -1;
+    }
+
+    /* This here's the one we want. */
+    if (out_score)
+        *out_score = bestscore;
+    if (out_is_final) {
+	fsg_link_t *fl;
+	hist_entry = fsg_history_entry_get(fsgs->history, besthist);
+	fl = fsg_hist_entry_fsglink(hist_entry);
+	*out_is_final = (fsg_link_to_state(fl) == fsg_model_final_state(fsg));
+    }
+    return besthist;
+}
+
+/* FIXME: Mostly duplicated with ngram_search_bestpath(). */
+static ps_latlink_t *
+fsg_search_bestpath(ps_search_t *search, int32 *out_score, int backward)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+
+    if (search->last_link == NULL) {
+        search->last_link = ps_lattice_bestpath(search->dag, NULL,
+                                                1.0, fsgs->ascale);
+        if (search->last_link == NULL)
+            return NULL;
+        /* Also calculate betas so we can fill in the posterior
+         * probability field in the segmentation. */
+        if (search->post == 0)
+            search->post = ps_lattice_posterior(search->dag, NULL, fsgs->ascale);
+    }
+    if (out_score)
+        *out_score = search->last_link->path_scr + search->dag->final_node_ascr;
+    return search->last_link;
+}
+
+char const *
+fsg_search_hyp(ps_search_t *search, int32 *out_score, int32 *out_is_final)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+    dict_t *dict = ps_search_dict(search);
+    char *c;
+    size_t len;
+    int bp, bpidx;
+
+    /* Get last backpointer table index. */
+    bpidx = fsg_search_find_exit(fsgs, fsgs->frame, fsgs->final, out_score, out_is_final);
+    /* No hypothesis (yet). */
+    if (bpidx <= 0) {
+        return NULL;
+    }
+
+    /* If bestpath is enabled and the utterance is complete, then run it. */
+    if (fsgs->bestpath && fsgs->final) {
+        ps_lattice_t *dag;
+        ps_latlink_t *link;
+
+        if ((dag = fsg_search_lattice(search)) == NULL) {
+    	    E_WARN("Failed to obtain the lattice while bestpath enabled\n");
+            return NULL;
+        }
+        if ((link = fsg_search_bestpath(search, out_score, FALSE)) == NULL) {
+    	    E_WARN("Failed to find the bestpath in a lattice\n");
+            return NULL;
+        }
+        return ps_lattice_hyp(dag, link);
+    }
+
+    bp = bpidx;
+    len = 0;
+    while (bp > 0) {
+        fsg_hist_entry_t *hist_entry = fsg_history_entry_get(fsgs->history, bp);
+        fsg_link_t *fl = fsg_hist_entry_fsglink(hist_entry);
+        char const *baseword;
+        int32 wid;
+
+        bp = fsg_hist_entry_pred(hist_entry);
+        wid = fsg_link_wid(fl);
+        if (wid < 0 || fsg_model_is_filler(fsgs->fsg, wid))
+            continue;
+        baseword = dict_basestr(dict,
+                                dict_wordid(dict,
+                                            fsg_model_word_str(fsgs->fsg, wid)));
+        len += strlen(baseword) + 1;
+    }
+    
+    ckd_free(search->hyp_str);
+    if (len == 0) {
+	search->hyp_str = NULL;
+	return search->hyp_str;
+    }
+    search->hyp_str = ckd_calloc(1, len);
+
+    bp = bpidx;
+    c = search->hyp_str + len - 1;
+    while (bp > 0) {
+        fsg_hist_entry_t *hist_entry = fsg_history_entry_get(fsgs->history, bp);
+        fsg_link_t *fl = fsg_hist_entry_fsglink(hist_entry);
+        char const *baseword;
+        int32 wid;
+
+        bp = fsg_hist_entry_pred(hist_entry);
+        wid = fsg_link_wid(fl);
+        if (wid < 0 || fsg_model_is_filler(fsgs->fsg, wid))
+            continue;
+        baseword = dict_basestr(dict,
+                                dict_wordid(dict,
+                                            fsg_model_word_str(fsgs->fsg, wid)));
+        len = strlen(baseword);
+        c -= len;
+        memcpy(c, baseword, len);
+        if (c > search->hyp_str) {
+            --c;
+            *c = ' ';
+        }
+    }
+
+    return search->hyp_str;
+}
+
+static void
+fsg_seg_bp2itor(ps_seg_t *seg, fsg_hist_entry_t *hist_entry)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)seg->search;
+    fsg_hist_entry_t *ph = NULL;
+    int32 bp;
+
+    if ((bp = fsg_hist_entry_pred(hist_entry)) >= 0)
+        ph = fsg_history_entry_get(fsgs->history, bp);
+    seg->word = fsg_model_word_str(fsgs->fsg, hist_entry->fsglink->wid);
+    seg->ef = fsg_hist_entry_frame(hist_entry);
+    seg->sf = ph ? fsg_hist_entry_frame(ph) + 1 : 0;
+    /* This is kind of silly but it happens for null transitions. */
+    if (seg->sf > seg->ef) seg->sf = seg->ef;
+    seg->prob = 0; /* Bogus value... */
+    /* "Language model" score = transition probability. */
+    seg->lback = 1;
+    seg->lscr = fsg_link_logs2prob(hist_entry->fsglink) >> SENSCR_SHIFT;
+    if (ph) {
+        /* FIXME: Not sure exactly how cross-word triphones are handled. */
+        seg->ascr = hist_entry->score - ph->score - seg->lscr;
+    }
+    else
+        seg->ascr = hist_entry->score - seg->lscr;
+}
+
+
+static void
+fsg_seg_free(ps_seg_t *seg)
+{
+    fsg_seg_t *itor = (fsg_seg_t *)seg;
+    ckd_free(itor->hist);
+    ckd_free(itor);
+}
+
+static ps_seg_t *
+fsg_seg_next(ps_seg_t *seg)
+{
+    fsg_seg_t *itor = (fsg_seg_t *)seg;
+
+    if (++itor->cur == itor->n_hist) {
+        fsg_seg_free(seg);
+        return NULL;
+    }
+
+    fsg_seg_bp2itor(seg, itor->hist[itor->cur]);
+    return seg;
+}
+
+static ps_segfuncs_t fsg_segfuncs = {
+    /* seg_next */ fsg_seg_next,
+    /* seg_free */ fsg_seg_free
+};
+
+static ps_seg_t *
+fsg_search_seg_iter(ps_search_t *search, int32 *out_score)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+    fsg_seg_t *itor;
+    int bp, bpidx, cur;
+
+    bpidx = fsg_search_find_exit(fsgs, fsgs->frame, fsgs->final, out_score, NULL);
+    /* No hypothesis (yet). */
+    if (bpidx <= 0)
+        return NULL;
+
+    /* If bestpath is enabled and the utterance is complete, then run it. */
+    if (fsgs->bestpath && fsgs->final) {
+        ps_lattice_t *dag;
+        ps_latlink_t *link;
+
+        if ((dag = fsg_search_lattice(search)) == NULL)
+            return NULL;
+        if ((link = fsg_search_bestpath(search, out_score, TRUE)) == NULL)
+            return NULL;
+        return ps_lattice_seg_iter(dag, link, 1.0);
+    }
+
+    /* Calling this an "iterator" is a bit of a misnomer since we have
+     * to get the entire backtrace in order to produce it.  On the
+     * other hand, all we actually need is the bptbl IDs, and we can
+     * allocate a fixed-size array of them. */
+    itor = ckd_calloc(1, sizeof(*itor));
+    itor->base.vt = &fsg_segfuncs;
+    itor->base.search = search;
+    itor->base.lwf = 1.0;
+    itor->n_hist = 0;
+    bp = bpidx;
+    while (bp > 0) {
+        fsg_hist_entry_t *hist_entry = fsg_history_entry_get(fsgs->history, bp);
+        bp = fsg_hist_entry_pred(hist_entry);
+        ++itor->n_hist;
+    }
+    if (itor->n_hist == 0) {
+        ckd_free(itor);
+        return NULL;
+    }
+    itor->hist = ckd_calloc(itor->n_hist, sizeof(*itor->hist));
+    cur = itor->n_hist - 1;
+    bp = bpidx;
+    while (bp > 0) {
+        fsg_hist_entry_t *hist_entry = fsg_history_entry_get(fsgs->history, bp);
+        itor->hist[cur] = hist_entry;
+        bp = fsg_hist_entry_pred(hist_entry);
+        --cur;
+    }
+
+    /* Fill in relevant fields for first element. */
+    fsg_seg_bp2itor((ps_seg_t *)itor, itor->hist[0]);
+    
+    return (ps_seg_t *)itor;
+}
+
+static int
+fsg_search_prob(ps_search_t *search)
+{
+    fsg_search_t *fsgs = (fsg_search_t *)search;
+
+    /* If bestpath is enabled and the utterance is complete, then run it. */
+    if (fsgs->bestpath && fsgs->final) {
+        ps_lattice_t *dag;
+        ps_latlink_t *link;
+
+        if ((dag = fsg_search_lattice(search)) == NULL)
+            return 0;
+        if ((link = fsg_search_bestpath(search, NULL, TRUE)) == NULL)
+            return 0;
+        return search->post;
+    }
+    else {
+        /* FIXME: Give some kind of good estimate here, eventually. */
+        return 0;
+    }
+}
+
+static ps_latnode_t *
+find_node(ps_lattice_t *dag, fsg_model_t *fsg, int sf, int32 wid, int32 node_id)
+{
+    ps_latnode_t *node;
+
+    for (node = dag->nodes; node; node = node->next)
+        if ((node->sf == sf) && (node->wid == wid) && (node->node_id == node_id))
+            break;
+    return node;
+}
+
+static ps_latnode_t *
+new_node(ps_lattice_t *dag, fsg_model_t *fsg, int sf, int ef, int32 wid, int32 node_id, int32 ascr)
+{
+    ps_latnode_t *node;
+
+    node = find_node(dag, fsg, sf, wid, node_id);
+
+    if (node) {
+        /* Update end frames. */
+        if (node->lef == -1 || node->lef < ef)
+            node->lef = ef;
+        if (node->fef == -1 || node->fef > ef)
+            node->fef = ef;
+        /* Update best link score. */
+        if (ascr BETTER_THAN node->info.best_exit)
+            node->info.best_exit = ascr;
+    }
+    else {
+        /* New node; link to head of list */
+        node = listelem_malloc(dag->latnode_alloc);
+        node->wid = wid;
+        node->sf = sf;
+        node->fef = node->lef = ef;
+        node->reachable = FALSE;
+        node->entries = NULL;
+        node->exits = NULL;
+        node->info.best_exit = ascr;
+        node->node_id = node_id;
+
+        node->next = dag->nodes;
+        dag->nodes = node;
+        ++dag->n_nodes;
+    }
+
+    return node;
+}
+
+static ps_latnode_t *
+find_start_node(fsg_search_t *fsgs, ps_lattice_t *dag)
+{
+    ps_latnode_t *node;
+    glist_t start = NULL;
+    int nstart = 0;
+
+    /* Look for all nodes starting in frame zero with some exits. */
+    for (node = dag->nodes; node; node = node->next) {
+        if (node->sf == 0 && node->exits) {
+            E_INFO("Start node %s.%d:%d:%d\n",
+                   fsg_model_word_str(fsgs->fsg, node->wid),
+                   node->sf, node->fef, node->lef);
+            start = glist_add_ptr(start, node);
+            ++nstart;
+        }
+    }
+
+    /* If there was more than one start node candidate, then we need
+     * to create an artificial start node with epsilon transitions to
+     * all of them. */
+    if (nstart == 1) {
+        node = gnode_ptr(start);
+    }
+    else {
+        gnode_t *st;
+        int wid;
+
+        wid = fsg_model_word_add(fsgs->fsg, "<s>");
+        if (fsgs->fsg->silwords)
+            bitvec_set(fsgs->fsg->silwords, wid);
+        node = new_node(dag, fsgs->fsg, 0, 0, wid, -1, 0);
+        for (st = start; st; st = gnode_next(st))
+            ps_lattice_link(dag, node, gnode_ptr(st), 0, 0);
+    }
+    glist_free(start);
+    return node;
+}
+
+static ps_latnode_t *
+find_end_node(fsg_search_t *fsgs, ps_lattice_t *dag)
+{
+    ps_latnode_t *node;
+    glist_t end = NULL;
+    int nend = 0;
+
+    /* Look for all nodes ending in last frame with some entries. */
+    for (node = dag->nodes; node; node = node->next) {
+        if (node->lef == dag->n_frames - 1 && node->entries) {
+            E_INFO("End node %s.%d:%d:%d (%d)\n",
+                   fsg_model_word_str(fsgs->fsg, node->wid),
+                   node->sf, node->fef, node->lef, node->info.best_exit);
+            end = glist_add_ptr(end, node);
+            ++nend;
+        }
+    }
+
+    if (nend == 1) {
+        node = gnode_ptr(end);
+    }
+    else if (nend == 0) {
+        ps_latnode_t *last = NULL;
+        int ef = 0;
+
+        /* If there were no end node candidates, then just use the
+         * node with the last exit frame. */
+        for (node = dag->nodes; node; node = node->next) {
+            if (node->lef > ef && node->entries) {
+                last = node;
+                ef = node->lef;
+            }
+        }
+        node = last;
+        if (node)
+            E_INFO("End node %s.%d:%d:%d (%d)\n",
+                   fsg_model_word_str(fsgs->fsg, node->wid),
+                   node->sf, node->fef, node->lef, node->info.best_exit);
+    }    
+    else {
+        /* If there was more than one end node candidate, then we need
+         * to create an artificial end node with epsilon transitions
+         * out of all of them. */
+        gnode_t *st;
+        int wid;
+        wid = fsg_model_word_add(fsgs->fsg, "</s>");
+        if (fsgs->fsg->silwords)
+            bitvec_set(fsgs->fsg->silwords, wid);
+        node = new_node(dag, fsgs->fsg, fsgs->frame, fsgs->frame, wid, -1, 0);
+        /* Use the "best" (in reality it will be the only) exit link
+         * score from this final node as the link score. */
+        for (st = end; st; st = gnode_next(st)) {
+            ps_latnode_t *src = gnode_ptr(st);
+            ps_lattice_link(dag, src, node, src->info.best_exit, fsgs->frame);
+        }
+    }
+    glist_free(end);
+    return node;
+}
+
+static void
+mark_reachable(ps_lattice_t *dag, ps_latnode_t *end)
+{
+    glist_t q;
+
+    /* It doesn't matter which order we do this in. */
+    end->reachable = TRUE;
+    q = glist_add_ptr(NULL, end);
+    while (q) {
+        ps_latnode_t *node = gnode_ptr(q);
+        latlink_list_t *x;
+
+        /* Pop the front of the list. */
+        q = gnode_free(q, NULL);
+        /* Expand all its predecessors that haven't been seen yet. */
+        for (x = node->entries; x; x = x->next) {
+            ps_latnode_t *next = x->link->from;
+            if (!next->reachable) {
+                next->reachable = TRUE;
+                q = glist_add_ptr(q, next);
+            }
+        }
+    }
+}
+
+/**
+ * Generate a lattice from FSG search results.
+ *
+ * One might think that this is simply a matter of adding acoustic
+ * scores to the FSG's edges.  However, one would be wrong.  The
+ * crucial difference here is that the word lattice is acyclic, and it
+ * also contains timing information.
+ */
+static ps_lattice_t *
+fsg_search_lattice(ps_search_t *search)
+{
+    fsg_search_t *fsgs;
+    fsg_model_t *fsg;
+    ps_latnode_t *node;
+    ps_lattice_t *dag;
+    int32 i, n;
+
+    fsgs = (fsg_search_t *)search;
+
+    /* Check to see if a lattice has previously been created over the
+     * same number of frames, and reuse it if so. */
+    if (search->dag && search->dag->n_frames == fsgs->frame)
+        return search->dag;
+
+    /* Nope, create a new one. */
+    ps_lattice_free(search->dag);
+    search->dag = NULL;
+    dag = ps_lattice_init_search(search, fsgs->frame);
+    fsg = fsgs->fsg;
+
+    /*
+     * Each history table entry represents a link in the word graph.
+     * The set of nodes is determined by the number of unique
+     * (word,start-frame) pairs in the history table.  So we will
+     * first find all those nodes.
+     */
+    n = fsg_history_n_entries(fsgs->history);
+    for (i = 0; i < n; ++i) {
+        fsg_hist_entry_t *fh = fsg_history_entry_get(fsgs->history, i);
+        int32 ascr;
+        int sf;
+
+        /* Skip null transitions. */
+        if (fh->fsglink == NULL || fh->fsglink->wid == -1)
+            continue;
+
+        /* Find the start node of this link. */
+        if (fh->pred) {
+            fsg_hist_entry_t *pfh = fsg_history_entry_get(fsgs->history, fh->pred);
+            /* FIXME: We include the transition score in the lattice
+             * link score.  This is because of the practical
+             * difficulty of obtaining it separately in bestpath or
+             * forward-backward search, and because it is essentially
+             * a unigram probability, so there is no need to treat it
+             * separately from the acoustic score.  However, it's not
+             * clear that this will actually yield correct results.*/
+            ascr = fh->score - pfh->score;
+            sf = pfh->frame + 1;
+        }
+        else {
+            ascr = fh->score;
+            sf = 0;
+        }
+
+        /*
+         * Note that although scores are tied to links rather than
+         * nodes, it's possible that there are no links out of the
+         * destination node, and thus we need to preserve its score in
+         * case it turns out to be utterance-final.
+         */
+        new_node(dag, fsg, sf, fh->frame, fh->fsglink->wid, fsg_link_to_state(fh->fsglink), ascr);
+    }
+
+    /*
+     * Now, we will create links only to nodes that actually exist.
+     */
+    n = fsg_history_n_entries(fsgs->history);
+    for (i = 0; i < n; ++i) {
+        fsg_hist_entry_t *fh = fsg_history_entry_get(fsgs->history, i);
+        fsg_arciter_t *itor;
+        ps_latnode_t *src, *dest;
+        int32 ascr;
+        int sf;
+
+        /* Skip null transitions. */
+        if (fh->fsglink == NULL || fh->fsglink->wid == -1)
+            continue;
+
+        /* Find the start node of this link and calculate its link score. */
+        if (fh->pred) {
+            fsg_hist_entry_t *pfh = fsg_history_entry_get(fsgs->history, fh->pred);
+            sf = pfh->frame + 1;
+            ascr = fh->score - pfh->score;
+        }
+        else {
+            ascr = fh->score;
+            sf = 0;
+        }
+        src = find_node(dag, fsg, sf, fh->fsglink->wid, fsg_link_to_state(fh->fsglink));
+        sf = fh->frame + 1;
+
+        for (itor = fsg_model_arcs(fsg, fsg_link_to_state(fh->fsglink));
+             itor; itor = fsg_arciter_next(itor)) {
+            fsg_link_t *link = fsg_arciter_get(itor);
+            
+            /* FIXME: Need to figure out what to do about tag transitions. */
+            if (link->wid >= 0) {
+                /*
+                 * For each non-epsilon link following this one, look for a
+                 * matching node in the lattice and link to it.
+                 */
+                if ((dest = find_node(dag, fsg, sf, link->wid, fsg_link_to_state(link))) != NULL)
+            	    ps_lattice_link(dag, src, dest, ascr, fh->frame);
+            }
+            else {
+                /*
+                 * Transitive closure on nulls has already been done, so we
+                 * just need to look one link forward from them.
+                 */
+                fsg_arciter_t *itor2;
+                
+                /* Add all non-null links out of j. */
+                for (itor2 = fsg_model_arcs(fsg, fsg_link_to_state(link));
+                     itor2; itor2 = fsg_arciter_next(itor2)) {
+                    fsg_link_t *link = fsg_arciter_get(itor2);
+
+                    if (link->wid == -1)
+                        continue;
+                    
+                    if ((dest = find_node(dag, fsg, sf, link->wid, fsg_link_to_state(link))) != NULL) {
+                        ps_lattice_link(dag, src, dest, ascr, fh->frame);
+                    }
+                }
+            }
+        }
+    }
+
+
+    /* Figure out which nodes are the start and end nodes. */
+    if ((dag->start = find_start_node(fsgs, dag)) == NULL) {
+	E_WARN("Failed to find the start node\n");
+        goto error_out;
+    }
+    if ((dag->end = find_end_node(fsgs, dag)) == NULL) {
+	E_WARN("Failed to find the end node\n");
+        goto error_out;
+    }
+
+
+    E_INFO("lattice start node %s.%d end node %s.%d\n",
+           fsg_model_word_str(fsg, dag->start->wid), dag->start->sf,
+           fsg_model_word_str(fsg, dag->end->wid), dag->end->sf);
+    /* FIXME: Need to calculate final_node_ascr here. */
+
+    /*
+     * Convert word IDs from FSG to dictionary.
+     */
+    for (node = dag->nodes; node; node = node->next) {
+        node->wid = dict_wordid(dag->search->dict,
+                                fsg_model_word_str(fsg, node->wid));
+        node->basewid = dict_basewid(dag->search->dict, node->wid);
+    }
+
+    /*
+     * Now we are done, because the links in the graph are uniquely
+     * defined by the history table.  However we should remove any
+     * nodes which are not reachable from the end node of the FSG.
+     * Everything is reachable from the start node by definition.
+     */
+    mark_reachable(dag, dag->end);
+
+    ps_lattice_delete_unreachable(dag);
+    {
+        int32 silpen, fillpen;
+
+        silpen = (int32)(logmath_log(fsg->lmath,
+                                     cmd_ln_float32_r(ps_search_config(fsgs), "-silprob"))
+                         * fsg->lw)
+            >> SENSCR_SHIFT;
+        fillpen = (int32)(logmath_log(fsg->lmath,
+                                      cmd_ln_float32_r(ps_search_config(fsgs), "-fillprob"))
+                          * fsg->lw)
+            >> SENSCR_SHIFT;
+	
+	ps_lattice_penalize_fillers(dag, silpen, fillpen);
+    }
+    search->dag = dag;
+
+    return dag;
+
+
+error_out:
+    ps_lattice_free(dag);
+    return NULL;
+
+}
+