Add m-esr52 at 52.6.0

1 files changed, 962 insertions, 0 deletions

diff --git a/media/pocketsphinx/src/ngram_search_fwdflat.c b/media/pocketsphinx/src/ngram_search_fwdflat.c
new file mode 100644
index 000000000..02becdc85
--- /dev/null
+++ b/media/pocketsphinx/src/ngram_search_fwdflat.c
@@ -0,0 +1,962 @@
+/* -*- 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_fwdflat.c Flat lexicon search.
+ */
+
+/* System headers. */
+#include <string.h>
+#include <assert.h>
+
+/* SphinxBase headers. */
+#include <sphinxbase/ckd_alloc.h>
+#include <sphinxbase/listelem_alloc.h>
+#include <sphinxbase/err.h>
+
+/* Local headers. */
+#include "ngram_search.h"
+#include "ps_lattice_internal.h"
+
+/* Turn this on to dump channels for debugging */
+#define __CHAN_DUMP__		0
+#if __CHAN_DUMP__
+#define chan_v_eval(chan) hmm_dump_vit_eval(&(chan)->hmm, stderr)
+#else
+#define chan_v_eval(chan) hmm_vit_eval(&(chan)->hmm)
+#endif
+
+static void
+ngram_fwdflat_expand_all(ngram_search_t *ngs)
+{
+    int n_words, i;
+
+    /* For all "real words" (not fillers or <s>/</s>) in the dictionary,
+     *
+     * 1) Add the ones which are in the LM to the fwdflat wordlist
+     * 2) And to the expansion list (since we are expanding all)
+     */
+    ngs->n_expand_words = 0;
+    n_words = ps_search_n_words(ngs);
+    bitvec_clear_all(ngs->expand_word_flag, ps_search_n_words(ngs));
+    for (i = 0; i < n_words; ++i) {
+        if (!ngram_model_set_known_wid(ngs->lmset,
+                                       dict_basewid(ps_search_dict(ngs),i)))
+            continue;
+        ngs->fwdflat_wordlist[ngs->n_expand_words] = i;
+        ngs->expand_word_list[ngs->n_expand_words] = i;
+        bitvec_set(ngs->expand_word_flag, i);
+        ngs->n_expand_words++;
+    }
+    E_INFO("Utterance vocabulary contains %d words\n", ngs->n_expand_words);
+    ngs->expand_word_list[ngs->n_expand_words] = -1;
+    ngs->fwdflat_wordlist[ngs->n_expand_words] = -1;
+}
+
+static void
+ngram_fwdflat_allocate_1ph(ngram_search_t *ngs)
+{
+    dict_t *dict = ps_search_dict(ngs);
+    int n_words = ps_search_n_words(ngs);
+    int i, w;
+
+    /* Allocate single-phone words, since they won't have
+     * been allocated for us by fwdtree initialization. */
+    ngs->n_1ph_words = 0;
+    for (w = 0; w < n_words; w++) {
+        if (dict_is_single_phone(dict, w))
+            ++ngs->n_1ph_words;
+    }
+    ngs->single_phone_wid = ckd_calloc(ngs->n_1ph_words,
+                                       sizeof(*ngs->single_phone_wid));
+    ngs->rhmm_1ph = ckd_calloc(ngs->n_1ph_words, sizeof(*ngs->rhmm_1ph));
+    i = 0;
+    for (w = 0; w < n_words; w++) {
+        if (!dict_is_single_phone(dict, w))
+            continue;
+
+        /* DICT2PID location */
+        ngs->rhmm_1ph[i].ciphone = dict_first_phone(dict, w);
+        ngs->rhmm_1ph[i].ci2phone = bin_mdef_silphone(ps_search_acmod(ngs)->mdef);
+        hmm_init(ngs->hmmctx, &ngs->rhmm_1ph[i].hmm, TRUE,
+                 /* ssid */ bin_mdef_pid2ssid(ps_search_acmod(ngs)->mdef,
+                                              ngs->rhmm_1ph[i].ciphone),
+                 /* tmatid */ bin_mdef_pid2tmatid(ps_search_acmod(ngs)->mdef,
+    						  ngs->rhmm_1ph[i].ciphone));
+        ngs->rhmm_1ph[i].next = NULL;
+        ngs->word_chan[w] = (chan_t *) &(ngs->rhmm_1ph[i]);
+        ngs->single_phone_wid[i] = w;
+        i++;
+    }
+}
+
+static void
+ngram_fwdflat_free_1ph(ngram_search_t *ngs)
+{
+    int i, w;
+    int n_words = ps_search_n_words(ngs);
+
+    for (i = w = 0; w < n_words; ++w) {
+        if (!dict_is_single_phone(ps_search_dict(ngs), w))
+            continue;
+        hmm_deinit(&ngs->rhmm_1ph[i].hmm);
+        ++i;
+    }
+    ckd_free(ngs->rhmm_1ph);
+    ngs->rhmm_1ph = NULL;
+    ckd_free(ngs->single_phone_wid);
+}
+
+void
+ngram_fwdflat_init(ngram_search_t *ngs)
+{
+    int n_words;
+
+    n_words = ps_search_n_words(ngs);
+    ngs->fwdflat_wordlist = ckd_calloc(n_words + 1, sizeof(*ngs->fwdflat_wordlist));
+    ngs->expand_word_flag = bitvec_alloc(n_words);
+    ngs->expand_word_list = ckd_calloc(n_words + 1, sizeof(*ngs->expand_word_list));
+    ngs->frm_wordlist = ckd_calloc(ngs->n_frame_alloc, sizeof(*ngs->frm_wordlist));
+    ngs->min_ef_width = cmd_ln_int32_r(ps_search_config(ngs), "-fwdflatefwid");
+    ngs->max_sf_win = cmd_ln_int32_r(ps_search_config(ngs), "-fwdflatsfwin");
+    E_INFO("fwdflat: min_ef_width = %d, max_sf_win = %d\n",
+           ngs->min_ef_width, ngs->max_sf_win);
+
+    /* No tree-search; pre-build the expansion list, including all LM words. */
+    if (!ngs->fwdtree) {
+        /* Build full expansion list from LM words. */
+        ngram_fwdflat_expand_all(ngs);
+        /* Allocate single phone words. */
+        ngram_fwdflat_allocate_1ph(ngs);
+    }
+}
+
+void
+ngram_fwdflat_deinit(ngram_search_t *ngs)
+{
+    double n_speech = (double)ngs->n_tot_frame
+            / cmd_ln_int32_r(ps_search_config(ngs), "-frate");
+
+    E_INFO("TOTAL fwdflat %.2f CPU %.3f xRT\n",
+           ngs->fwdflat_perf.t_tot_cpu,
+           ngs->fwdflat_perf.t_tot_cpu / n_speech);
+    E_INFO("TOTAL fwdflat %.2f wall %.3f xRT\n",
+           ngs->fwdflat_perf.t_tot_elapsed,
+           ngs->fwdflat_perf.t_tot_elapsed / n_speech);
+
+    /* Free single-phone words if we allocated them. */
+    if (!ngs->fwdtree) {
+        ngram_fwdflat_free_1ph(ngs);
+    }
+    ckd_free(ngs->fwdflat_wordlist);
+    bitvec_free(ngs->expand_word_flag);
+    ckd_free(ngs->expand_word_list);
+    ckd_free(ngs->frm_wordlist);
+}
+
+int
+ngram_fwdflat_reinit(ngram_search_t *ngs)
+{
+    /* Reallocate things that depend on the number of words. */
+    int n_words;
+
+    ckd_free(ngs->fwdflat_wordlist);
+    ckd_free(ngs->expand_word_list);
+    bitvec_free(ngs->expand_word_flag);
+    n_words = ps_search_n_words(ngs);
+    ngs->fwdflat_wordlist = ckd_calloc(n_words + 1, sizeof(*ngs->fwdflat_wordlist));
+    ngs->expand_word_flag = bitvec_alloc(n_words);
+    ngs->expand_word_list = ckd_calloc(n_words + 1, sizeof(*ngs->expand_word_list));
+    
+    /* No tree-search; take care of the expansion list and single phone words. */
+    if (!ngs->fwdtree) {
+        /* Free single-phone words. */
+        ngram_fwdflat_free_1ph(ngs);
+        /* Reallocate word_chan. */
+        ckd_free(ngs->word_chan);
+        ngs->word_chan = ckd_calloc(dict_size(ps_search_dict(ngs)),
+                                    sizeof(*ngs->word_chan));
+        /* Rebuild full expansion list from LM words. */
+        ngram_fwdflat_expand_all(ngs);
+        /* Allocate single phone words. */
+        ngram_fwdflat_allocate_1ph(ngs);
+    }
+    /* Otherwise there is nothing to do since the wordlist is
+     * generated anew every utterance. */
+    return 0;
+}
+
+/**
+ * Find all active words in backpointer table and sort by frame.
+ */
+static void
+build_fwdflat_wordlist(ngram_search_t *ngs)
+{
+    int32 i, f, sf, ef, wid, nwd;
+    bptbl_t *bp;
+    ps_latnode_t *node, *prevnode, *nextnode;
+
+    /* No tree-search, use statically allocated wordlist. */
+    if (!ngs->fwdtree)
+        return;
+
+    memset(ngs->frm_wordlist, 0, ngs->n_frame_alloc * sizeof(*ngs->frm_wordlist));
+
+    /* Scan the backpointer table for all active words and record
+     * their exit frames. */
+    for (i = 0, bp = ngs->bp_table; i < ngs->bpidx; i++, bp++) {
+        sf = (bp->bp < 0) ? 0 : ngs->bp_table[bp->bp].frame + 1;
+        ef = bp->frame;
+        wid = bp->wid;
+
+        /* Anything that can be transitioned to in the LM can go in
+         * the word list. */
+        if (!ngram_model_set_known_wid(ngs->lmset,
+                                       dict_basewid(ps_search_dict(ngs), wid)))
+            continue;
+
+        /* Look for it in the wordlist. */
+        for (node = ngs->frm_wordlist[sf]; node && (node->wid != wid);
+             node = node->next);
+
+        /* Update last end frame. */
+        if (node)
+            node->lef = ef;
+        else {
+            /* New node; link to head of list */
+            node = listelem_malloc(ngs->latnode_alloc);
+            node->wid = wid;
+            node->fef = node->lef = ef;
+
+            node->next = ngs->frm_wordlist[sf];
+            ngs->frm_wordlist[sf] = node;
+        }
+    }
+
+    /* Eliminate "unlikely" words, for which there are too few end points */
+    for (f = 0; f < ngs->n_frame; f++) {
+        prevnode = NULL;
+        for (node = ngs->frm_wordlist[f]; node; node = nextnode) {
+            nextnode = node->next;
+            /* Word has too few endpoints */
+            if ((node->lef - node->fef < ngs->min_ef_width) ||
+                /* Word is </s> and doesn't actually end in last frame */
+                ((node->wid == ps_search_finish_wid(ngs)) && (node->lef < ngs->n_frame - 1))) {
+                if (!prevnode)
+                    ngs->frm_wordlist[f] = nextnode;
+                else
+                    prevnode->next = nextnode;
+                listelem_free(ngs->latnode_alloc, node);
+            }
+            else
+                prevnode = node;
+        }
+    }
+
+    /* Form overall wordlist for 2nd pass */
+    nwd = 0;
+    bitvec_clear_all(ngs->word_active, ps_search_n_words(ngs));
+    for (f = 0; f < ngs->n_frame; f++) {
+        for (node = ngs->frm_wordlist[f]; node; node = node->next) {
+            if (!bitvec_is_set(ngs->word_active, node->wid)) {
+                bitvec_set(ngs->word_active, node->wid);
+                ngs->fwdflat_wordlist[nwd++] = node->wid;
+            }
+        }
+    }
+    ngs->fwdflat_wordlist[nwd] = -1;
+    E_INFO("Utterance vocabulary contains %d words\n", nwd);
+}
+
+/**
+ * Build HMM network for one utterance of fwdflat search.
+ */
+static void
+build_fwdflat_chan(ngram_search_t *ngs)
+{
+    int32 i, wid, p;
+    root_chan_t *rhmm;
+    chan_t *hmm, *prevhmm;
+    dict_t *dict;
+    dict2pid_t *d2p;
+
+    dict = ps_search_dict(ngs);
+    d2p = ps_search_dict2pid(ngs);
+
+    /* Build word HMMs for each word in the lattice. */
+    for (i = 0; ngs->fwdflat_wordlist[i] >= 0; i++) {
+        wid = ngs->fwdflat_wordlist[i];
+
+        /* Single-phone words are permanently allocated */
+        if (dict_is_single_phone(dict, wid))
+            continue;
+
+        assert(ngs->word_chan[wid] == NULL);
+
+        /* Multiplex root HMM for first phone (one root per word, flat
+         * lexicon).  diphone is irrelevant here, for the time being,
+         * at least. */
+        rhmm = listelem_malloc(ngs->root_chan_alloc);
+        rhmm->ci2phone = dict_second_phone(dict, wid);
+        rhmm->ciphone = dict_first_phone(dict, wid);
+        rhmm->next = NULL;
+        hmm_init(ngs->hmmctx, &rhmm->hmm, TRUE,
+                 bin_mdef_pid2ssid(ps_search_acmod(ngs)->mdef, rhmm->ciphone),
+                 bin_mdef_pid2tmatid(ps_search_acmod(ngs)->mdef, rhmm->ciphone));
+
+        /* HMMs for word-internal phones */
+        prevhmm = NULL;
+        for (p = 1; p < dict_pronlen(dict, wid) - 1; p++) {
+            hmm = listelem_malloc(ngs->chan_alloc);
+            hmm->ciphone = dict_pron(dict, wid, p);
+            hmm->info.rc_id = (p == dict_pronlen(dict, wid) - 1) ? 0 : -1;
+            hmm->next = NULL;
+            hmm_init(ngs->hmmctx, &hmm->hmm, FALSE,
+                     dict2pid_internal(d2p,wid,p), 
+		     bin_mdef_pid2tmatid(ps_search_acmod(ngs)->mdef, hmm->ciphone));
+
+            if (prevhmm)
+                prevhmm->next = hmm;
+            else
+                rhmm->next = hmm;
+
+            prevhmm = hmm;
+        }
+
+        /* Right-context phones */
+        ngram_search_alloc_all_rc(ngs, wid);
+
+        /* Link in just allocated right-context phones */
+        if (prevhmm)
+            prevhmm->next = ngs->word_chan[wid];
+        else
+            rhmm->next = ngs->word_chan[wid];
+        ngs->word_chan[wid] = (chan_t *) rhmm;
+    }
+
+}
+
+void
+ngram_fwdflat_start(ngram_search_t *ngs)
+{
+    root_chan_t *rhmm;
+    int i;
+
+    ptmr_reset(&ngs->fwdflat_perf);
+    ptmr_start(&ngs->fwdflat_perf);
+    build_fwdflat_wordlist(ngs);
+    build_fwdflat_chan(ngs);
+
+    ngs->bpidx = 0;
+    ngs->bss_head = 0;
+
+    for (i = 0; i < ps_search_n_words(ngs); i++)
+        ngs->word_lat_idx[i] = NO_BP;
+
+    /* Reset the permanently allocated single-phone words, since they
+     * may have junk left over in them from previous searches. */
+    for (i = 0; i < ngs->n_1ph_words; i++) {
+        int32 w = ngs->single_phone_wid[i];
+        rhmm = (root_chan_t *) ngs->word_chan[w];
+        hmm_clear(&rhmm->hmm);
+    }
+
+    /* Start search with <s>; word_chan[<s>] is permanently allocated */
+    rhmm = (root_chan_t *) ngs->word_chan[ps_search_start_wid(ngs)];
+    hmm_enter(&rhmm->hmm, 0, NO_BP, 0);
+    ngs->active_word_list[0][0] = ps_search_start_wid(ngs);
+    ngs->n_active_word[0] = 1;
+
+    ngs->best_score = 0;
+    ngs->renormalized = FALSE;
+
+    for (i = 0; i < ps_search_n_words(ngs); i++)
+        ngs->last_ltrans[i].sf = -1;
+
+    if (!ngs->fwdtree)
+        ngs->n_frame = 0;
+
+    ngs->st.n_fwdflat_chan = 0;
+    ngs->st.n_fwdflat_words = 0;
+    ngs->st.n_fwdflat_word_transition = 0;
+    ngs->st.n_senone_active_utt = 0;
+}
+
+static void
+compute_fwdflat_sen_active(ngram_search_t *ngs, int frame_idx)
+{
+    int32 i, nw, w;
+    int32 *awl;
+    root_chan_t *rhmm;
+    chan_t *hmm;
+
+    acmod_clear_active(ps_search_acmod(ngs));
+
+    nw = ngs->n_active_word[frame_idx & 0x1];
+    awl = ngs->active_word_list[frame_idx & 0x1];
+
+    for (i = 0; i < nw; i++) {
+        w = *(awl++);
+        rhmm = (root_chan_t *)ngs->word_chan[w];
+        if (hmm_frame(&rhmm->hmm) == frame_idx) {
+            acmod_activate_hmm(ps_search_acmod(ngs), &rhmm->hmm);
+        }
+
+        for (hmm = rhmm->next; hmm; hmm = hmm->next) {
+            if (hmm_frame(&hmm->hmm) == frame_idx) {
+                acmod_activate_hmm(ps_search_acmod(ngs), &hmm->hmm);
+            }
+        }
+    }
+}
+
+static void
+fwdflat_eval_chan(ngram_search_t *ngs, int frame_idx)
+{
+    int32 i, w, nw, bestscore;
+    int32 *awl;
+    root_chan_t *rhmm;
+    chan_t *hmm;
+
+    nw = ngs->n_active_word[frame_idx & 0x1];
+    awl = ngs->active_word_list[frame_idx & 0x1];
+    bestscore = WORST_SCORE;
+
+    ngs->st.n_fwdflat_words += nw;
+
+    /* Scan all active words. */
+    for (i = 0; i < nw; i++) {
+        w = *(awl++);
+        rhmm = (root_chan_t *) ngs->word_chan[w];
+        if (hmm_frame(&rhmm->hmm) == frame_idx) {
+            int32 score = chan_v_eval(rhmm);
+            if ((score BETTER_THAN bestscore) && (w != ps_search_finish_wid(ngs)))
+                bestscore = score;
+            ngs->st.n_fwdflat_chan++;
+        }
+
+        for (hmm = rhmm->next; hmm; hmm = hmm->next) {
+            if (hmm_frame(&hmm->hmm) == frame_idx) {
+                int32 score = chan_v_eval(hmm);
+                if (score BETTER_THAN bestscore)
+                    bestscore = score;
+                ngs->st.n_fwdflat_chan++;
+            }
+        }
+    }
+
+    ngs->best_score = bestscore;
+}
+
+static void
+fwdflat_prune_chan(ngram_search_t *ngs, int frame_idx)
+{
+    int32 i, nw, cf, nf, w, pip, newscore, thresh, wordthresh;
+    int32 *awl;
+    root_chan_t *rhmm;
+    chan_t *hmm, *nexthmm;
+
+    cf = frame_idx;
+    nf = cf + 1;
+    nw = ngs->n_active_word[cf & 0x1];
+    awl = ngs->active_word_list[cf & 0x1];
+    bitvec_clear_all(ngs->word_active, ps_search_n_words(ngs));
+
+    thresh = ngs->best_score + ngs->fwdflatbeam;
+    wordthresh = ngs->best_score + ngs->fwdflatwbeam;
+    pip = ngs->pip;
+    E_DEBUG(3,("frame %d thresh %d wordthresh %d\n", frame_idx, thresh, wordthresh));
+
+    /* Scan all active words. */
+    for (i = 0; i < nw; i++) {
+        w = *(awl++);
+        rhmm = (root_chan_t *) ngs->word_chan[w];
+        /* Propagate active root channels */
+        if (hmm_frame(&rhmm->hmm) == cf
+            && hmm_bestscore(&rhmm->hmm) BETTER_THAN thresh) {
+            hmm_frame(&rhmm->hmm) = nf;
+            bitvec_set(ngs->word_active, w);
+
+            /* Transitions out of root channel */
+            newscore = hmm_out_score(&rhmm->hmm);
+            if (rhmm->next) {
+                assert(!dict_is_single_phone(ps_search_dict(ngs), w));
+
+                newscore += pip;
+                if (newscore BETTER_THAN thresh) {
+                    hmm = rhmm->next;
+                    /* Enter all right context phones */
+                    if (hmm->info.rc_id >= 0) {
+                        for (; hmm; hmm = hmm->next) {
+                            if ((hmm_frame(&hmm->hmm) < cf)
+                                || (newscore BETTER_THAN hmm_in_score(&hmm->hmm))) {
+                                hmm_enter(&hmm->hmm, newscore,
+                                          hmm_out_history(&rhmm->hmm), nf);
+                            }
+                        }
+                    }
+                    /* Just a normal word internal phone */
+                    else {
+                        if ((hmm_frame(&hmm->hmm) < cf)
+                            || (newscore BETTER_THAN hmm_in_score(&hmm->hmm))) {
+                                hmm_enter(&hmm->hmm, newscore,
+                                          hmm_out_history(&rhmm->hmm), nf);
+                        }
+                    }
+                }
+            }
+            else {
+                assert(dict_is_single_phone(ps_search_dict(ngs), w));
+
+                /* Word exit for single-phone words (where did their
+                 * whmms come from?) (either from
+                 * ngram_search_fwdtree, or from
+                 * ngram_fwdflat_allocate_1ph(), that's where) */
+                if (newscore BETTER_THAN wordthresh) {
+                    ngram_search_save_bp(ngs, cf, w, newscore,
+                                         hmm_out_history(&rhmm->hmm), 0);
+                }
+            }
+        }
+
+        /* Transitions out of non-root channels. */
+        for (hmm = rhmm->next; hmm; hmm = hmm->next) {
+            if (hmm_frame(&hmm->hmm) >= cf) {
+                /* Propagate forward HMMs inside the beam. */
+                if (hmm_bestscore(&hmm->hmm) BETTER_THAN thresh) {
+                    hmm_frame(&hmm->hmm) = nf;
+                    bitvec_set(ngs->word_active, w);
+
+                    newscore = hmm_out_score(&hmm->hmm);
+                    /* Word-internal phones */
+                    if (hmm->info.rc_id < 0) {
+                        newscore += pip;
+                        if (newscore BETTER_THAN thresh) {
+                            nexthmm = hmm->next;
+                            /* Enter all right-context phones. */
+                            if (nexthmm->info.rc_id >= 0) {
+                                 for (; nexthmm; nexthmm = nexthmm->next) {
+                                    if ((hmm_frame(&nexthmm->hmm) < cf)
+                                        || (newscore BETTER_THAN
+                                            hmm_in_score(&nexthmm->hmm))) {
+                                        hmm_enter(&nexthmm->hmm,
+                                                  newscore,
+                                                  hmm_out_history(&hmm->hmm),
+                                                  nf);
+                                    }
+                                }
+                            }
+                            /* Enter single word-internal phone. */
+                            else {
+                                if ((hmm_frame(&nexthmm->hmm) < cf)
+                                    || (newscore BETTER_THAN
+                                        hmm_in_score(&nexthmm->hmm))) {
+                                    hmm_enter(&nexthmm->hmm, newscore,
+                                              hmm_out_history(&hmm->hmm), nf);
+                                }
+                            }
+                        }
+                    }
+                    /* Right-context phones - apply word beam and exit. */
+                    else {
+                        if (newscore BETTER_THAN wordthresh) {
+                            ngram_search_save_bp(ngs, cf, w, newscore,
+                                                 hmm_out_history(&hmm->hmm),
+                                                 hmm->info.rc_id);
+                        }
+                    }
+                }
+                /* Zero out inactive HMMs. */
+                else if (hmm_frame(&hmm->hmm) != nf) {
+                    hmm_clear_scores(&hmm->hmm);
+                }
+            }
+        }
+    }
+}
+
+static void
+get_expand_wordlist(ngram_search_t *ngs, int32 frm, int32 win)
+{
+    int32 f, sf, ef;
+    ps_latnode_t *node;
+
+    if (!ngs->fwdtree) {
+        ngs->st.n_fwdflat_word_transition += ngs->n_expand_words;
+        return;
+    }
+
+    sf = frm - win;
+    if (sf < 0)
+        sf = 0;
+    ef = frm + win;
+    if (ef > ngs->n_frame)
+        ef = ngs->n_frame;
+
+    bitvec_clear_all(ngs->expand_word_flag, ps_search_n_words(ngs));
+    ngs->n_expand_words = 0;
+
+    for (f = sf; f < ef; f++) {
+        for (node = ngs->frm_wordlist[f]; node; node = node->next) {
+            if (!bitvec_is_set(ngs->expand_word_flag, node->wid)) {
+                ngs->expand_word_list[ngs->n_expand_words++] = node->wid;
+                bitvec_set(ngs->expand_word_flag, node->wid);
+            }
+        }
+    }
+    ngs->expand_word_list[ngs->n_expand_words] = -1;
+    ngs->st.n_fwdflat_word_transition += ngs->n_expand_words;
+}
+
+static void
+fwdflat_word_transition(ngram_search_t *ngs, int frame_idx)
+{
+    int32 cf, nf, b, thresh, pip, i, nw, w, newscore;
+    int32 best_silrc_score = 0, best_silrc_bp = 0;      /* FIXME: good defaults? */
+    bptbl_t *bp;
+    int32 *rcss;
+    root_chan_t *rhmm;
+    int32 *awl;
+    float32 lwf;
+    dict_t *dict = ps_search_dict(ngs);
+    dict2pid_t *d2p = ps_search_dict2pid(ngs);
+
+    cf = frame_idx;
+    nf = cf + 1;
+    thresh = ngs->best_score + ngs->fwdflatbeam;
+    pip = ngs->pip;
+    best_silrc_score = WORST_SCORE;
+    lwf = ngs->fwdflat_fwdtree_lw_ratio;
+
+    /* Search for all words starting within a window of this frame.
+     * These are the successors for words exiting now. */
+    get_expand_wordlist(ngs, cf, ngs->max_sf_win);
+
+    /* Scan words exited in current frame */
+    for (b = ngs->bp_table_idx[cf]; b < ngs->bpidx; b++) {
+        xwdssid_t *rssid;
+        int32 silscore;
+
+        bp = ngs->bp_table + b;
+        ngs->word_lat_idx[bp->wid] = NO_BP;
+
+        if (bp->wid == ps_search_finish_wid(ngs))
+            continue;
+
+        /* DICT2PID location */
+        /* Get the mapping from right context phone ID to index in the
+         * right context table and the bscore_stack. */
+        rcss = ngs->bscore_stack + bp->s_idx;
+        if (bp->last2_phone == -1)
+            rssid = NULL;
+        else
+            rssid = dict2pid_rssid(d2p, bp->last_phone, bp->last2_phone);
+
+        /* Transition to all successor words. */
+        for (i = 0; ngs->expand_word_list[i] >= 0; i++) {
+            int32 n_used;
+
+            w = ngs->expand_word_list[i];
+
+            /* Get the exit score we recorded in save_bwd_ptr(), or
+             * something approximating it. */
+            if (rssid)
+                newscore = rcss[rssid->cimap[dict_first_phone(dict, w)]];
+            else
+                newscore = bp->score;
+            if (newscore == WORST_SCORE)
+                continue;
+            /* FIXME: Floating point... */
+            newscore += lwf
+                * (ngram_tg_score(ngs->lmset,
+                                  dict_basewid(dict, w),
+                                  bp->real_wid,
+                                  bp->prev_real_wid,
+                                  &n_used) >> SENSCR_SHIFT);
+            newscore += pip;
+
+            /* Enter the next word */
+            if (newscore BETTER_THAN thresh) {
+                rhmm = (root_chan_t *) ngs->word_chan[w];
+                if ((hmm_frame(&rhmm->hmm) < cf)
+                    || (newscore BETTER_THAN hmm_in_score(&rhmm->hmm))) {
+                    hmm_enter(&rhmm->hmm, newscore, b, nf);
+                    /* DICT2PID: This is where mpx ssids get introduced. */
+                    /* Look up the ssid to use when entering this mpx triphone. */
+                    hmm_mpx_ssid(&rhmm->hmm, 0) =
+                        dict2pid_ldiph_lc(d2p, rhmm->ciphone, rhmm->ci2phone,
+                                          dict_last_phone(dict, bp->wid));
+                    assert(IS_S3SSID(hmm_mpx_ssid(&rhmm->hmm, 0)));
+                    E_DEBUG(6,("ssid %d(%d,%d) = %d\n",
+                               rhmm->ciphone, dict_last_phone(dict, bp->wid), rhmm->ci2phone,
+                               hmm_mpx_ssid(&rhmm->hmm, 0)));
+                    bitvec_set(ngs->word_active, w);
+                }
+            }
+        }
+
+        /* Get the best exit into silence. */
+        if (rssid)
+            silscore = rcss[rssid->cimap[ps_search_acmod(ngs)->mdef->sil]];
+        else
+            silscore = bp->score;
+        if (silscore BETTER_THAN best_silrc_score) {
+            best_silrc_score = silscore;
+            best_silrc_bp = b;
+        }
+    }
+
+    /* Transition to <sil> */
+    newscore = best_silrc_score + ngs->silpen + pip;
+    if ((newscore BETTER_THAN thresh) && (newscore BETTER_THAN WORST_SCORE)) {
+        w = ps_search_silence_wid(ngs);
+        rhmm = (root_chan_t *) ngs->word_chan[w];
+        if ((hmm_frame(&rhmm->hmm) < cf)
+            || (newscore BETTER_THAN hmm_in_score(&rhmm->hmm))) {
+            hmm_enter(&rhmm->hmm, newscore,
+                      best_silrc_bp, nf);
+            bitvec_set(ngs->word_active, w);
+        }
+    }
+    /* Transition to noise words */
+    newscore = best_silrc_score + ngs->fillpen + pip;
+    if ((newscore BETTER_THAN thresh) && (newscore BETTER_THAN WORST_SCORE)) {
+        for (w = ps_search_silence_wid(ngs) + 1; w < ps_search_n_words(ngs); w++) {
+            rhmm = (root_chan_t *) ngs->word_chan[w];
+            /* Noise words that aren't a single phone will have NULL here. */
+            if (rhmm == NULL)
+                continue;
+            if ((hmm_frame(&rhmm->hmm) < cf)
+                || (newscore BETTER_THAN hmm_in_score(&rhmm->hmm))) {
+                hmm_enter(&rhmm->hmm, newscore,
+                          best_silrc_bp, nf);
+                bitvec_set(ngs->word_active, w);
+            }
+        }
+    }
+
+    /* Reset initial channels of words that have become inactive even after word trans. */
+    nw = ngs->n_active_word[cf & 0x1];
+    awl = ngs->active_word_list[cf & 0x1];
+    for (i = 0; i < nw; i++) {
+        w = *(awl++);
+        rhmm = (root_chan_t *) ngs->word_chan[w];
+        if (hmm_frame(&rhmm->hmm) == cf) {
+            hmm_clear_scores(&rhmm->hmm);
+        }
+    }
+}
+
+static void
+fwdflat_renormalize_scores(ngram_search_t *ngs, int frame_idx, int32 norm)
+{
+    root_chan_t *rhmm;
+    chan_t *hmm;
+    int32 i, nw, cf, w, *awl;
+
+    cf = frame_idx;
+
+    /* Renormalize individual word channels */
+    nw = ngs->n_active_word[cf & 0x1];
+    awl = ngs->active_word_list[cf & 0x1];
+    for (i = 0; i < nw; i++) {
+        w = *(awl++);
+        rhmm = (root_chan_t *) ngs->word_chan[w];
+        if (hmm_frame(&rhmm->hmm) == cf) {
+            hmm_normalize(&rhmm->hmm, norm);
+        }
+        for (hmm = rhmm->next; hmm; hmm = hmm->next) {
+            if (hmm_frame(&hmm->hmm) == cf) {
+                hmm_normalize(&hmm->hmm, norm);
+            }
+        }
+    }
+
+    ngs->renormalized = TRUE;
+}
+
+int
+ngram_fwdflat_search(ngram_search_t *ngs, int frame_idx)
+{
+    int16 const *senscr;
+    int32 nf, i, j;
+    int32 *nawl;
+
+    /* Activate our HMMs for the current frame if need be. */
+    if (!ps_search_acmod(ngs)->compallsen)
+        compute_fwdflat_sen_active(ngs, frame_idx);
+
+    /* Compute GMM scores for the current frame. */
+    senscr = acmod_score(ps_search_acmod(ngs), &frame_idx);
+    ngs->st.n_senone_active_utt += ps_search_acmod(ngs)->n_senone_active;
+
+    /* Mark backpointer table for current frame. */
+    ngram_search_mark_bptable(ngs, frame_idx);
+
+    /* If the best score is equal to or worse than WORST_SCORE,
+     * recognition has failed, don't bother to keep trying. */
+    if (ngs->best_score == WORST_SCORE || ngs->best_score WORSE_THAN WORST_SCORE)
+        return 0;
+    /* Renormalize if necessary */
+    if (ngs->best_score + (2 * ngs->beam) WORSE_THAN WORST_SCORE) {
+        E_INFO("Renormalizing Scores at frame %d, best score %d\n",
+               frame_idx, ngs->best_score);
+        fwdflat_renormalize_scores(ngs, frame_idx, ngs->best_score);
+    }
+
+    ngs->best_score = WORST_SCORE;
+    hmm_context_set_senscore(ngs->hmmctx, senscr);
+
+    /* Evaluate HMMs */
+    fwdflat_eval_chan(ngs, frame_idx);
+    /* Prune HMMs and do phone transitions. */
+    fwdflat_prune_chan(ngs, frame_idx);
+    /* Do word transitions. */
+    fwdflat_word_transition(ngs, frame_idx);
+
+    /* Create next active word list, skip fillers */
+    nf = frame_idx + 1;
+    nawl = ngs->active_word_list[nf & 0x1];
+    for (i = 0, j = 0; ngs->fwdflat_wordlist[i] >= 0; i++) {
+        int32 wid = ngs->fwdflat_wordlist[i];
+        if (bitvec_is_set(ngs->word_active, wid) && wid < ps_search_start_wid(ngs)) {
+            *(nawl++) = wid;
+            j++;
+        }
+    }
+    /* Add fillers */
+    for (i = ps_search_start_wid(ngs); i < ps_search_n_words(ngs); i++) {
+        if (bitvec_is_set(ngs->word_active, i)) {
+            *(nawl++) = i;
+            j++;
+        }
+    }
+    if (!ngs->fwdtree)
+        ++ngs->n_frame;
+    ngs->n_active_word[nf & 0x1] = j;
+
+    /* Return the number of frames processed. */
+    return 1;
+}
+
+/**
+ * Destroy wordlist from the current utterance.
+ */
+static void
+destroy_fwdflat_wordlist(ngram_search_t *ngs)
+{
+    ps_latnode_t *node, *tnode;
+    int32 f;
+
+    if (!ngs->fwdtree)
+        return;
+
+    for (f = 0; f < ngs->n_frame; f++) {
+        for (node = ngs->frm_wordlist[f]; node; node = tnode) {
+            tnode = node->next;
+            listelem_free(ngs->latnode_alloc, node);
+        }
+    }
+}
+
+/**
+ * Free HMM network for one utterance of fwdflat search.
+ */
+static void
+destroy_fwdflat_chan(ngram_search_t *ngs)
+{
+    int32 i, wid;
+
+    for (i = 0; ngs->fwdflat_wordlist[i] >= 0; i++) {
+        root_chan_t *rhmm;
+        chan_t *thmm;
+        wid = ngs->fwdflat_wordlist[i];
+        if (dict_is_single_phone(ps_search_dict(ngs),wid))
+            continue;
+        assert(ngs->word_chan[wid] != NULL);
+
+        /* The first HMM in ngs->word_chan[wid] was allocated with
+         * ngs->root_chan_alloc, but this will attempt to free it
+         * using ngs->chan_alloc, which will not work.  Therefore we
+         * free it manually and move the list forward before handing
+         * it off. */
+        rhmm = (root_chan_t *)ngs->word_chan[wid];
+        thmm = rhmm->next;
+        listelem_free(ngs->root_chan_alloc, rhmm);
+        ngs->word_chan[wid] = thmm;
+        ngram_search_free_all_rc(ngs, wid);
+    }
+}
+
+void
+ngram_fwdflat_finish(ngram_search_t *ngs)
+{
+    int32 cf;
+
+    destroy_fwdflat_chan(ngs);
+    destroy_fwdflat_wordlist(ngs);
+    bitvec_clear_all(ngs->word_active, ps_search_n_words(ngs));
+
+    /* This is the number of frames processed. */
+    cf = ps_search_acmod(ngs)->output_frame;
+    /* Add a mark in the backpointer table for one past the final frame. */
+    ngram_search_mark_bptable(ngs, cf);
+
+    ptmr_stop(&ngs->fwdflat_perf);
+    /* Print out some statistics. */
+    if (cf > 0) {
+        double n_speech = (double)(cf + 1)
+            / cmd_ln_int32_r(ps_search_config(ngs), "-frate");
+        E_INFO("%8d words recognized (%d/fr)\n",
+               ngs->bpidx, (ngs->bpidx + (cf >> 1)) / (cf + 1));
+        E_INFO("%8d senones evaluated (%d/fr)\n", ngs->st.n_senone_active_utt,
+               (ngs->st.n_senone_active_utt + (cf >> 1)) / (cf + 1));
+        E_INFO("%8d channels searched (%d/fr)\n",
+               ngs->st.n_fwdflat_chan, ngs->st.n_fwdflat_chan / (cf + 1));
+        E_INFO("%8d words searched (%d/fr)\n",
+               ngs->st.n_fwdflat_words, ngs->st.n_fwdflat_words / (cf + 1));
+        E_INFO("%8d word transitions (%d/fr)\n",
+               ngs->st.n_fwdflat_word_transition,
+               ngs->st.n_fwdflat_word_transition / (cf + 1));
+        E_INFO("fwdflat %.2f CPU %.3f xRT\n",
+               ngs->fwdflat_perf.t_cpu,
+               ngs->fwdflat_perf.t_cpu / n_speech);
+        E_INFO("fwdflat %.2f wall %.3f xRT\n",
+               ngs->fwdflat_perf.t_elapsed,
+               ngs->fwdflat_perf.t_elapsed / n_speech);
+    }
+}