#include "decoder/lattice-faster-decoder.h"

#include "lat/lattice-functions.h"

namespace kaldi {

template <typename FST, typename Token>

LatticeFasterDecoderTpl<FST, Token>::LatticeFasterDecoderTpl(

const FST &fst,

const LatticeFasterDecoderConfig &config):

fst_(&fst), delete_fst_(false), config_(config), num_toks_(0) {

config.Check();

toks_.SetSize(1000); // just so on the first frame we do something reasonable.

}

template <typename FST, typename Token>

LatticeFasterDecoderTpl<FST, Token>::LatticeFasterDecoderTpl(

const LatticeFasterDecoderConfig &config, FST *fst):

fst_(fst), delete_fst_(true), config_(config), num_toks_(0) {

config.Check();

toks_.SetSize(1000); // just so on the first frame we do something reasonable.

}

template <typename FST, typename Token>

LatticeFasterDecoderTpl<FST, Token>::~LatticeFasterDecoderTpl() {

DeleteElems(toks_.Clear());

ClearActiveTokens();

if (delete_fst_) delete fst_;

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::InitDecoding() {

// clean up from last time:

DeleteElems(toks_.Clear());

cost_offsets_.clear();

ClearActiveTokens();

warned_ = false;

num_toks_ = 0;

decoding_finalized_ = false;

final_costs_.clear();

StateId start_state = fst_->Start();

KALDI_ASSERT(start_state != fst::kNoStateId);

active_toks_.resize(1);

Token *start_tok = new Token(0.0, 0.0, NULL, NULL, NULL);

active_toks_[0].toks = start_tok;

toks_.Insert(start_state, start_tok);

num_toks_++;

ProcessNonemitting(config_.beam);

}

template <typename FST, typename Token>

bool LatticeFasterDecoderTpl<FST, Token>::Decode(DecodableInterface *decodable) {

InitDecoding();

// We use 1-based indexing for frames in this decoder (if you view it in

// terms of features), but note that the decodable object uses zero-based

// numbering, which we have to correct for when we call it.

while (!decodable->IsLastFrame(NumFramesDecoded() - 1)) {

if (NumFramesDecoded() % config_.prune_interval == 0)

PruneActiveTokens(config_.lattice_beam * config_.prune_scale);

BaseFloat cost_cutoff = ProcessEmitting(decodable);

ProcessNonemitting(cost_cutoff);

}

FinalizeDecoding();

// Returns true if we have any kind of traceback available (not necessarily

// to the end state; query ReachedFinal() for that).

return !active_toks_.empty() && active_toks_.back().toks != NULL;

}

template <typename FST, typename Token>

bool LatticeFasterDecoderTpl<FST, Token>::GetBestPath(Lattice *olat,

bool use_final_probs) const {

Lattice raw_lat;

GetRawLattice(&raw_lat, use_final_probs);

ShortestPath(raw_lat, olat);

return (olat->NumStates() != 0);

}

template <typename FST, typename Token>

bool LatticeFasterDecoderTpl<FST, Token>::GetRawLattice(

Lattice *ofst,

bool use_final_probs) const {

typedef LatticeArc Arc;

typedef Arc::StateId StateId;

typedef Arc::Weight Weight;

typedef Arc::Label Label;

// Note: you can't use the old interface (Decode()) if you want to

// get the lattice with use_final_probs = false. You'd have to do

// InitDecoding() and then AdvanceDecoding().

if (decoding_finalized_ && !use_final_probs)

KALDI_ERR << "You cannot call FinalizeDecoding() and then call "

<< "GetRawLattice() with use_final_probs == false";

unordered_map<Token*, BaseFloat> final_costs_local;

const unordered_map<Token*, BaseFloat> &final_costs =

(decoding_finalized_ ? final_costs_ : final_costs_local);

if (!decoding_finalized_ && use_final_probs)

ComputeFinalCosts(&final_costs_local, NULL, NULL);

ofst->DeleteStates();

// num-frames plus one (since frames are one-based, and we have

// an extra frame for the start-state).

int32 num_frames = active_toks_.size() - 1;

KALDI_ASSERT(num_frames > 0);

const int32 bucket_count = num_toks_/2 + 3;

unordered_map<Token*, StateId> tok_map(bucket_count);

// First create all states.

std::vector<Token*> token_list;

for (int32 f = 0; f <= num_frames; f++) {

if (active_toks_[f].toks == NULL) {

KALDI_WARN << "GetRawLattice: no tokens active on frame " << f

<< ": not producing lattice.\n";

return false;

}

TopSortTokens(active_toks_[f].toks, &token_list);

for (size_t i = 0; i < token_list.size(); i++)

if (token_list[i] != NULL)

tok_map[token_list[i]] = ofst->AddState();

}

// The next statement sets the start state of the output FST. Because we

// topologically sorted the tokens, state zero must be the start-state.

ofst->SetStart(0);

KALDI_VLOG(4) << "init:" << num_toks_/2 + 3 << " buckets:"

<< tok_map.bucket_count() << " load:" << tok_map.load_factor()

<< " max:" << tok_map.max_load_factor();

// Now create all arcs.

for (int32 f = 0; f <= num_frames; f++) {

for (Token *tok = active_toks_[f].toks; tok != NULL; tok = tok->next) {

StateId cur_state = tok_map[tok];

for (ForwardLinkT *l = tok->links;

l != NULL;

l = l->next) {

typename unordered_map<Token*, StateId>::const_iterator

iter = tok_map.find(l->next_tok);

StateId nextstate = iter->second;

KALDI_ASSERT(iter != tok_map.end());

BaseFloat cost_offset = 0.0;

if (l->ilabel != 0) { // emitting..

KALDI_ASSERT(f >= 0 && f < cost_offsets_.size());

cost_offset = cost_offsets_[f];

}

Arc arc(l->ilabel, l->olabel,

Weight(l->graph_cost, l->acoustic_cost - cost_offset),

nextstate);

ofst->AddArc(cur_state, arc);

}

if (f == num_frames) {

if (use_final_probs && !final_costs.empty()) {

typename unordered_map<Token*, BaseFloat>::const_iterator

iter = final_costs.find(tok);

if (iter != final_costs.end())

ofst->SetFinal(cur_state, LatticeWeight(iter->second, 0));

} else {

ofst->SetFinal(cur_state, LatticeWeight::One());

}

}

}

}

return (ofst->NumStates() > 0);

}

template <typename FST, typename Token>

bool LatticeFasterDecoderTpl<FST, Token>::GetLattice(CompactLattice *ofst,

bool use_final_probs) const {

Lattice raw_fst;

GetRawLattice(&raw_fst, use_final_probs);

Invert(&raw_fst); // make it so word labels are on the input.

// (in phase where we get backward-costs).

fst::ILabelCompare<LatticeArc> ilabel_comp;

ArcSort(&raw_fst, ilabel_comp); // sort on ilabel; makes

// lattice-determinization more efficient.

fst::DeterminizeLatticePrunedOptions lat_opts;

lat_opts.max_mem = config_.det_opts.max_mem;

DeterminizeLatticePruned(raw_fst, config_.lattice_beam, ofst, lat_opts);

raw_fst.DeleteStates(); // Free memory-- raw_fst no longer needed.

Connect(ofst); // Remove unreachable states... there might be

// a small number of these, in some cases.

// Note: if something went wrong and the raw lattice was empty,

// we should still get to this point in the code without warnings or failures.

return (ofst->NumStates() != 0);

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::PossiblyResizeHash(size_t num_toks) {

size_t new_sz = static_cast<size_t>(static_cast<BaseFloat>(num_toks)

* config_.hash_ratio);

if (new_sz > toks_.Size()) {

toks_.SetSize(new_sz);

}

}

template <typename FST, typename Token>

inline typename LatticeFasterDecoderTpl<FST, Token>::Elem*

LatticeFasterDecoderTpl<FST, Token>::FindOrAddToken(

StateId state, int32 frame_plus_one, BaseFloat tot_cost,

Token *backpointer, bool *changed) {

// Returns the Token pointer. Sets "changed" (if non-NULL) to true

// if the token was newly created or the cost changed.

KALDI_ASSERT(frame_plus_one < active_toks_.size());

Token *&toks = active_toks_[frame_plus_one].toks;

Elem *e_found = toks_.Insert(state, NULL);

if (e_found->val == NULL) { // no such token presently.

const BaseFloat extra_cost = 0.0;

// tokens on the currently final frame have zero extra_cost

// as any of them could end up

// on the winning path.

Token *new_tok = new Token (tot_cost, extra_cost, NULL, toks, backpointer);

// NULL: no forward links yet

toks = new_tok;

num_toks_++;

e_found->val = new_tok;

if (changed) *changed = true;

return e_found;

} else {

Token *tok = e_found->val; // There is an existing Token for this state.

if (tok->tot_cost > tot_cost) { // replace old token

tok->tot_cost = tot_cost;

// SetBackpointer() just does tok->backpointer = backpointer in

// the case where Token == BackpointerToken, else nothing.

tok->SetBackpointer(backpointer);

// we don't allocate a new token, the old stays linked in active_toks_

// we only replace the tot_cost

// in the current frame, there are no forward links (and no extra_cost)

// only in ProcessNonemitting we have to delete forward links

// in case we visit a state for the second time

// those forward links, that lead to this replaced token before:

// they remain and will hopefully be pruned later (PruneForwardLinks...)

if (changed) *changed = true;

} else {

if (changed) *changed = false;

}

return e_found;

}

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::PruneForwardLinks(

int32 frame_plus_one, bool *extra_costs_changed,

bool *links_pruned, BaseFloat delta) {

// delta is the amount by which the extra_costs must change

// If delta is larger, we'll tend to go back less far

// toward the beginning of the file.

// extra_costs_changed is set to true if extra_cost was changed for any token

// links_pruned is set to true if any link in any token was pruned

*extra_costs_changed = false;

*links_pruned = false;

KALDI_ASSERT(frame_plus_one >= 0 && frame_plus_one < active_toks_.size());

if (active_toks_[frame_plus_one].toks == NULL) { // empty list; should not happen.

if (!warned_) {

KALDI_WARN << "No tokens alive [doing pruning].. warning first "

"time only for each utterance\n";

warned_ = true;

}

}

// We have to iterate until there is no more change, because the links

// are not guaranteed to be in topological order.

bool changed = true; // difference new minus old extra cost >= delta ?

while (changed) {

changed = false;

for (Token *tok = active_toks_[frame_plus_one].toks;

tok != NULL; tok = tok->next) {

ForwardLinkT *link, *prev_link = NULL;

// will recompute tok_extra_cost for tok.

BaseFloat tok_extra_cost = std::numeric_limits<BaseFloat>::infinity();

// tok_extra_cost is the best (min) of link_extra_cost of outgoing links

for (link = tok->links; link != NULL; ) {

// See if we need to excise this link...

Token *next_tok = link->next_tok;

BaseFloat link_extra_cost = next_tok->extra_cost +

((tok->tot_cost + link->acoustic_cost + link->graph_cost)

- next_tok->tot_cost); // difference in brackets is >= 0

// link_exta_cost is the difference in score between the best paths

// through link source state and through link destination state

KALDI_ASSERT(link_extra_cost == link_extra_cost); // check for NaN

if (link_extra_cost > config_.lattice_beam) { // excise link

ForwardLinkT *next_link = link->next;

if (prev_link != NULL) prev_link->next = next_link;

else tok->links = next_link;

delete link;

link = next_link; // advance link but leave prev_link the same.

*links_pruned = true;

} else { // keep the link and update the tok_extra_cost if needed.

if (link_extra_cost < 0.0) { // this is just a precaution.

if (link_extra_cost < -0.01)

KALDI_WARN << "Negative extra_cost: " << link_extra_cost;

link_extra_cost = 0.0;

}

if (link_extra_cost < tok_extra_cost)

tok_extra_cost = link_extra_cost;

prev_link = link; // move to next link

link = link->next;

}

} // for all outgoing links

if (fabs(tok_extra_cost - tok->extra_cost) > delta)

changed = true; // difference new minus old is bigger than delta

tok->extra_cost = tok_extra_cost;

// will be +infinity or <= lattice_beam_.

// infinity indicates, that no forward link survived pruning

} // for all Token on active_toks_[frame]

if (changed) *extra_costs_changed = true;

// Note: it's theoretically possible that aggressive compiler

// optimizations could cause an infinite loop here for small delta and

// high-dynamic-range scores.

} // while changed

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::PruneForwardLinksFinal() {

KALDI_ASSERT(!active_toks_.empty());

int32 frame_plus_one = active_toks_.size() - 1;

if (active_toks_[frame_plus_one].toks == NULL) // empty list; should not happen.

KALDI_WARN << "No tokens alive at end of file";

typedef typename unordered_map<Token*, BaseFloat>::const_iterator IterType;

ComputeFinalCosts(&final_costs_, &final_relative_cost_, &final_best_cost_);

decoding_finalized_ = true;

// We call DeleteElems() as a nicety, not because it's really necessary;

// otherwise there would be a time, after calling PruneTokensForFrame() on the

// final frame, when toks_.GetList() or toks_.Clear() would contain pointers

// to nonexistent tokens.

DeleteElems(toks_.Clear());

// Now go through tokens on this frame, pruning forward links... may have to

// iterate a few times until there is no more change, because the list is not

// in topological order. This is a modified version of the code in

// PruneForwardLinks, but here we also take account of the final-probs.

bool changed = true;

BaseFloat delta = 1.0e-05;

while (changed) {

changed = false;

for (Token *tok = active_toks_[frame_plus_one].toks;

tok != NULL; tok = tok->next) {

ForwardLinkT *link, *prev_link = NULL;

// will recompute tok_extra_cost. It has a term in it that corresponds

// to the "final-prob", so instead of initializing tok_extra_cost to infinity

// below we set it to the difference between the (score+final_prob) of this token,

// and the best such (score+final_prob).

BaseFloat final_cost;

if (final_costs_.empty()) {

final_cost = 0.0;

} else {

IterType iter = final_costs_.find(tok);

if (iter != final_costs_.end())

final_cost = iter->second;

else

final_cost = std::numeric_limits<BaseFloat>::infinity();

}

BaseFloat tok_extra_cost = tok->tot_cost + final_cost - final_best_cost_;

// tok_extra_cost will be a "min" over either directly being final, or

// being indirectly final through other links, and the loop below may

// decrease its value:

for (link = tok->links; link != NULL; ) {

// See if we need to excise this link...

Token *next_tok = link->next_tok;

BaseFloat link_extra_cost = next_tok->extra_cost +

((tok->tot_cost + link->acoustic_cost + link->graph_cost)

- next_tok->tot_cost);

if (link_extra_cost > config_.lattice_beam) { // excise link

ForwardLinkT *next_link = link->next;

if (prev_link != NULL) prev_link->next = next_link;

else tok->links = next_link;

delete link;

link = next_link; // advance link but leave prev_link the same.

} else { // keep the link and update the tok_extra_cost if needed.

if (link_extra_cost < 0.0) { // this is just a precaution.

if (link_extra_cost < -0.01)

KALDI_WARN << "Negative extra_cost: " << link_extra_cost;

link_extra_cost = 0.0;

}

if (link_extra_cost < tok_extra_cost)

tok_extra_cost = link_extra_cost;

prev_link = link;

link = link->next;

}

}

// prune away tokens worse than lattice_beam above best path. This step

// was not necessary in the non-final case because then, this case

// showed up as having no forward links. Here, the tok_extra_cost has

// an extra component relating to the final-prob.

if (tok_extra_cost > config_.lattice_beam)

tok_extra_cost = std::numeric_limits<BaseFloat>::infinity();

// to be pruned in PruneTokensForFrame

if (!ApproxEqual(tok->extra_cost, tok_extra_cost, delta))

changed = true;

tok->extra_cost = tok_extra_cost; // will be +infinity or <= lattice_beam_.

}

} // while changed

}

template <typename FST, typename Token>

BaseFloat LatticeFasterDecoderTpl<FST, Token>::FinalRelativeCost() const {

if (!decoding_finalized_) {

BaseFloat relative_cost;

ComputeFinalCosts(NULL, &relative_cost, NULL);

return relative_cost;

} else {

// we're not allowed to call that function if FinalizeDecoding() has

// been called; return a cached value.

return final_relative_cost_;

}

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::PruneTokensForFrame(int32 frame_plus_one) {

KALDI_ASSERT(frame_plus_one >= 0 && frame_plus_one < active_toks_.size());

Token *&toks = active_toks_[frame_plus_one].toks;

if (toks == NULL)

KALDI_WARN << "No tokens alive [doing pruning]";

Token *tok, *next_tok, *prev_tok = NULL;

for (tok = toks; tok != NULL; tok = next_tok) {

next_tok = tok->next;

if (tok->extra_cost == std::numeric_limits<BaseFloat>::infinity()) {

// token is unreachable from end of graph; (no forward links survived)

// excise tok from list and delete tok.

if (prev_tok != NULL) prev_tok->next = tok->next;

else toks = tok->next;

delete tok;

num_toks_--;

} else { // fetch next Token

prev_tok = tok;

}

}

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::PruneActiveTokens(BaseFloat delta) {

int32 cur_frame_plus_one = NumFramesDecoded();

int32 num_toks_begin = num_toks_;

// The index "f" below represents a "frame plus one", i.e. you'd have to subtract

// one to get the corresponding index for the decodable object.

for (int32 f = cur_frame_plus_one - 1; f >= 0; f--) {

// Reason why we need to prune forward links in this situation:

// (1) we have never pruned them (new TokenList)

// (2) we have not yet pruned the forward links to the next f,

// after any of those tokens have changed their extra_cost.

if (active_toks_[f].must_prune_forward_links) {

bool extra_costs_changed = false, links_pruned = false;

PruneForwardLinks(f, &extra_costs_changed, &links_pruned, delta);

if (extra_costs_changed && f > 0) // any token has changed extra_cost

active_toks_[f-1].must_prune_forward_links = true;

if (links_pruned) // any link was pruned

active_toks_[f].must_prune_tokens = true;

active_toks_[f].must_prune_forward_links = false; // job done

}

if (f+1 < cur_frame_plus_one && // except for last f (no forward links)

active_toks_[f+1].must_prune_tokens) {

PruneTokensForFrame(f+1);

active_toks_[f+1].must_prune_tokens = false;

}

}

KALDI_VLOG(4) << "PruneActiveTokens: pruned tokens from " << num_toks_begin

<< " to " << num_toks_;

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::ComputeFinalCosts(

unordered_map<Token*, BaseFloat> *final_costs,

BaseFloat *final_relative_cost,

BaseFloat *final_best_cost) const {

KALDI_ASSERT(!decoding_finalized_);

if (final_costs != NULL)

final_costs->clear();

const Elem *final_toks = toks_.GetList();

BaseFloat infinity = std::numeric_limits<BaseFloat>::infinity();

BaseFloat best_cost = infinity,

best_cost_with_final = infinity;

while (final_toks != NULL) {

StateId state = final_toks->key;

Token *tok = final_toks->val;

const Elem *next = final_toks->tail;

BaseFloat final_cost = fst_->Final(state).Value();

BaseFloat cost = tok->tot_cost,

cost_with_final = cost + final_cost;

best_cost = std::min(cost, best_cost);

best_cost_with_final = std::min(cost_with_final, best_cost_with_final);

if (final_costs != NULL && final_cost != infinity)

(*final_costs)[tok] = final_cost;

final_toks = next;

}

if (final_relative_cost != NULL) {

if (best_cost == infinity && best_cost_with_final == infinity) {

// Likely this will only happen if there are no tokens surviving.

// This seems the least bad way to handle it.

*final_relative_cost = infinity;

} else {

*final_relative_cost = best_cost_with_final - best_cost;

}

}

if (final_best_cost != NULL) {

if (best_cost_with_final != infinity) { // final-state exists.

*final_best_cost = best_cost_with_final;

} else { // no final-state exists.

*final_best_cost = best_cost;

}

}

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::AdvanceDecoding(DecodableInterface *decodable,

int32 max_num_frames) {

if (std::is_same<FST, fst::Fst<fst::StdArc> >::value) {

// if the type 'FST' is the FST base-class, then see if the FST type of fst_

// is actually VectorFst or ConstFst. If so, call the AdvanceDecoding()

// function after casting *this to the more specific type.

if (fst_->Type() == "const") {

LatticeFasterDecoderTpl<fst::ConstFst<fst::StdArc>, Token> *this_cast =

reinterpret_cast<LatticeFasterDecoderTpl<fst::ConstFst<fst::StdArc>, Token>* >(this);

this_cast->AdvanceDecoding(decodable, max_num_frames);

return;

} else if (fst_->Type() == "vector") {

LatticeFasterDecoderTpl<fst::VectorFst<fst::StdArc>, Token> *this_cast =

reinterpret_cast<LatticeFasterDecoderTpl<fst::VectorFst<fst::StdArc>, Token>* >(this);

this_cast->AdvanceDecoding(decodable, max_num_frames);

return;

}

}

KALDI_ASSERT(!active_toks_.empty() && !decoding_finalized_ &&

"You must call InitDecoding() before AdvanceDecoding");

int32 num_frames_ready = decodable->NumFramesReady();

// num_frames_ready must be >= num_frames_decoded, or else

// the number of frames ready must have decreased (which doesn't

// make sense) or the decodable object changed between calls

// (which isn't allowed).

KALDI_ASSERT(num_frames_ready >= NumFramesDecoded());

int32 target_frames_decoded = num_frames_ready;

if (max_num_frames >= 0)

target_frames_decoded = std::min(target_frames_decoded,

NumFramesDecoded() + max_num_frames);

while (NumFramesDecoded() < target_frames_decoded) {

if (NumFramesDecoded() % config_.prune_interval == 0) {

PruneActiveTokens(config_.lattice_beam * config_.prune_scale);

}

BaseFloat cost_cutoff = ProcessEmitting(decodable);

ProcessNonemitting(cost_cutoff);

}

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::FinalizeDecoding() {

int32 final_frame_plus_one = NumFramesDecoded();

int32 num_toks_begin = num_toks_;

// PruneForwardLinksFinal() prunes final frame (with final-probs), and

// sets decoding_finalized_.

PruneForwardLinksFinal();

for (int32 f = final_frame_plus_one - 1; f >= 0; f--) {

bool b1, b2; // values not used.

BaseFloat dontcare = 0.0; // delta of zero means we must always update

PruneForwardLinks(f, &b1, &b2, dontcare);

PruneTokensForFrame(f + 1);

}

PruneTokensForFrame(0);

KALDI_VLOG(4) << "pruned tokens from " << num_toks_begin

<< " to " << num_toks_;

}

template <typename FST, typename Token>

BaseFloat LatticeFasterDecoderTpl<FST, Token>::GetCutoff(Elem *list_head, size_t *tok_count,

BaseFloat *adaptive_beam, Elem **best_elem) {

BaseFloat best_weight = std::numeric_limits<BaseFloat>::infinity();

// positive == high cost == bad.

size_t count = 0;

if (config_.max_active == std::numeric_limits<int32>::max() &&

config_.min_active == 0) {

for (Elem *e = list_head; e != NULL; e = e->tail, count++) {

BaseFloat w = static_cast<BaseFloat>(e->val->tot_cost);

if (w < best_weight) {

best_weight = w;

if (best_elem) *best_elem = e;

}

}

if (tok_count != NULL) *tok_count = count;

if (adaptive_beam != NULL) *adaptive_beam = config_.beam;

return best_weight + config_.beam;

} else {

tmp_array_.clear();

for (Elem *e = list_head; e != NULL; e = e->tail, count++) {

BaseFloat w = e->val->tot_cost;

tmp_array_.push_back(w);

if (w < best_weight) {

best_weight = w;

if (best_elem) *best_elem = e;

}

}

if (tok_count != NULL) *tok_count = count;

BaseFloat beam_cutoff = best_weight + config_.beam,

min_active_cutoff = std::numeric_limits<BaseFloat>::infinity(),

max_active_cutoff = std::numeric_limits<BaseFloat>::infinity();

KALDI_VLOG(6) << "Number of tokens active on frame " << NumFramesDecoded()

<< " is " << tmp_array_.size();

if (tmp_array_.size() > static_cast<size_t>(config_.max_active)) {

std::nth_element(tmp_array_.begin(),

tmp_array_.begin() + config_.max_active,

tmp_array_.end());

max_active_cutoff = tmp_array_[config_.max_active];

}

if (max_active_cutoff < beam_cutoff) { // max_active is tighter than beam.

if (adaptive_beam)

*adaptive_beam = max_active_cutoff - best_weight + config_.beam_delta;

return max_active_cutoff;

}

if (tmp_array_.size() > static_cast<size_t>(config_.min_active)) {

if (config_.min_active == 0) min_active_cutoff = best_weight;

else {

std::nth_element(tmp_array_.begin(),

tmp_array_.begin() + config_.min_active,

tmp_array_.size() > static_cast<size_t>(config_.max_active) ?

tmp_array_.begin() + config_.max_active :

tmp_array_.end());

min_active_cutoff = tmp_array_[config_.min_active];

}

}

if (min_active_cutoff > beam_cutoff) { // min_active is looser than beam.

if (adaptive_beam)

*adaptive_beam = min_active_cutoff - best_weight + config_.beam_delta;

return min_active_cutoff;

} else {

*adaptive_beam = config_.beam;

return beam_cutoff;

}

}

}

template <typename FST, typename Token>

BaseFloat LatticeFasterDecoderTpl<FST, Token>::ProcessEmitting(

DecodableInterface *decodable) {

KALDI_ASSERT(active_toks_.size() > 0);

int32 frame = active_toks_.size() - 1; // frame is the frame-index

// (zero-based) used to get likelihoods

// from the decodable object.

active_toks_.resize(active_toks_.size() + 1);

Elem *final_toks = toks_.Clear(); // analogous to swapping prev_toks_ / cur_toks_

// in simple-decoder.h. Removes the Elems from

// being indexed in the hash in toks_.

Elem *best_elem = NULL;

BaseFloat adaptive_beam;

size_t tok_cnt;

BaseFloat cur_cutoff = GetCutoff(final_toks, &tok_cnt, &adaptive_beam, &best_elem);

KALDI_VLOG(6) << "Adaptive beam on frame " << NumFramesDecoded() << " is "

<< adaptive_beam;

PossiblyResizeHash(tok_cnt); // This makes sure the hash is always big enough.

BaseFloat next_cutoff = std::numeric_limits<BaseFloat>::infinity();

// pruning "online" before having seen all tokens

BaseFloat cost_offset = 0.0; // Used to keep probabilities in a good

// dynamic range.

// First process the best token to get a hopefully

// reasonably tight bound on the next cutoff. The only

// products of the next block are "next_cutoff" and "cost_offset".

if (best_elem) {

StateId state = best_elem->key;

Token *tok = best_elem->val;

cost_offset = - tok->tot_cost;

for (fst::ArcIterator<FST> aiter(*fst_, state);

!aiter.Done();

aiter.Next()) {

const Arc &arc = aiter.Value();

if (arc.ilabel != 0) { // propagate..

BaseFloat new_weight = arc.weight.Value() + cost_offset -

decodable->LogLikelihood(frame, arc.ilabel) + tok->tot_cost;

if (new_weight + adaptive_beam < next_cutoff)

next_cutoff = new_weight + adaptive_beam;

}

}

}

// Store the offset on the acoustic likelihoods that we're applying.

// Could just do cost_offsets_.push_back(cost_offset), but we

// do it this way as it's more robust to future code changes.

cost_offsets_.resize(frame + 1, 0.0);

cost_offsets_[frame] = cost_offset;

// the tokens are now owned here, in final_toks, and the hash is empty.

// 'owned' is a complex thing here; the point is we need to call DeleteElem

// on each elem 'e' to let toks_ know we're done with them.

for (Elem *e = final_toks, *e_tail; e != NULL; e = e_tail) {

// loop this way because we delete "e" as we go.

StateId state = e->key;

Token *tok = e->val;

if (tok->tot_cost <= cur_cutoff) {

for (fst::ArcIterator<FST> aiter(*fst_, state);

!aiter.Done();

aiter.Next()) {

const Arc &arc = aiter.Value();

if (arc.ilabel != 0) { // propagate..

BaseFloat ac_cost = cost_offset -

decodable->LogLikelihood(frame, arc.ilabel),

graph_cost = arc.weight.Value(),

cur_cost = tok->tot_cost,

tot_cost = cur_cost + ac_cost + graph_cost;

if (tot_cost > next_cutoff) continue;

else if (tot_cost + adaptive_beam < next_cutoff)

next_cutoff = tot_cost + adaptive_beam; // prune by best current token

// Note: the frame indexes into active_toks_ are one-based,

// hence the + 1.

Elem *e_next = FindOrAddToken(arc.nextstate,

frame + 1, tot_cost, tok, NULL);

// NULL: no change indicator needed

// Add ForwardLink from tok to next_tok (put on head of list tok->links)

tok->links = new ForwardLinkT(e_next->val, arc.ilabel, arc.olabel,

graph_cost, ac_cost, tok->links);

}

} // for all arcs

}

e_tail = e->tail;

toks_.Delete(e); // delete Elem

}

return next_cutoff;

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::DeleteForwardLinks(Token *tok) {

ForwardLinkT *l = tok->links, *m;

while (l != NULL) {

m = l->next;

delete l;

l = m;

}

tok->links = NULL;

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::ProcessNonemitting(BaseFloat cutoff) {

KALDI_ASSERT(!active_toks_.empty());

int32 frame = static_cast<int32>(active_toks_.size()) - 2;

// Note: "frame" is the time-index we just processed, or -1 if

// we are processing the nonemitting transitions before the

// first frame (called from InitDecoding()).

// Processes nonemitting arcs for one frame. Propagates within toks_.

// Note-- this queue structure is not very optimal as

// it may cause us to process states unnecessarily (e.g. more than once),

// but in the baseline code, turning this vector into a set to fix this

// problem did not improve overall speed.

KALDI_ASSERT(queue_.empty());

if (toks_.GetList() == NULL) {

if (!warned_) {

KALDI_WARN << "Error, no surviving tokens: frame is " << frame;

warned_ = true;

}

}

for (const Elem *e = toks_.GetList(); e != NULL; e = e->tail) {

StateId state = e->key;

if (fst_->NumInputEpsilons(state) != 0)

queue_.push_back(e);

}

while (!queue_.empty()) {

const Elem *e = queue_.back();

queue_.pop_back();

StateId state = e->key;

Token *tok = e->val; // would segfault if e is a NULL pointer but this can't happen.

BaseFloat cur_cost = tok->tot_cost;

if (cur_cost > cutoff) // Don't bother processing successors.

continue;

// If "tok" has any existing forward links, delete them,

// because we're about to regenerate them. This is a kind

// of non-optimality (remember, this is the simple decoder),

// but since most states are emitting it's not a huge issue.

DeleteForwardLinks(tok); // necessary when re-visiting

tok->links = NULL;

for (fst::ArcIterator<FST> aiter(*fst_, state);

!aiter.Done();

aiter.Next()) {

const Arc &arc = aiter.Value();

if (arc.ilabel == 0) { // propagate nonemitting only...

BaseFloat graph_cost = arc.weight.Value(),

tot_cost = cur_cost + graph_cost;

if (tot_cost < cutoff) {

bool changed;

Elem *e_new = FindOrAddToken(arc.nextstate, frame + 1, tot_cost,

tok, &changed);

tok->links = new ForwardLinkT(e_new->val, 0, arc.olabel,

graph_cost, 0, tok->links);

// "changed" tells us whether the new token has a different

// cost from before, or is new [if so, add into queue].

if (changed && fst_->NumInputEpsilons(arc.nextstate) != 0)

queue_.push_back(e_new);

}

}

} // for all arcs

} // while queue not empty

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::DeleteElems(Elem *list) {

for (Elem *e = list, *e_tail; e != NULL; e = e_tail) {

e_tail = e->tail;

toks_.Delete(e);

}

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::ClearActiveTokens() { // a cleanup routine, at utt end/begin

for (size_t i = 0; i < active_toks_.size(); i++) {

// Delete all tokens alive on this frame, and any forward

// links they may have.

for (Token *tok = active_toks_[i].toks; tok != NULL; ) {

DeleteForwardLinks(tok);

Token *next_tok = tok->next;

delete tok;

num_toks_--;

tok = next_tok;

}

}

active_toks_.clear();

KALDI_ASSERT(num_toks_ == 0);

}

template <typename FST, typename Token>

void LatticeFasterDecoderTpl<FST, Token>::TopSortTokens(

Token *tok_list, std::vector<Token*> *topsorted_list) {

unordered_map<Token*, int32> token2pos;

typedef typename unordered_map<Token*, int32>::iterator IterType;

int32 num_toks = 0;

for (Token *tok = tok_list; tok != NULL; tok = tok->next)

num_toks++;

int32 cur_pos = 0;

// We assign the tokens numbers num_toks - 1, ... , 2, 1, 0.

// This is likely to be in closer to topological order than

// if we had given them ascending order, because of the way

// new tokens are put at the front of the list.

for (Token *tok = tok_list; tok != NULL; tok = tok->next)

token2pos[tok] = num_toks - ++cur_pos;

unordered_set<Token*> reprocess;

for (IterType iter = token2pos.begin(); iter != token2pos.end(); ++iter) {

Token *tok = iter->first;

int32 pos = iter->second;

for (ForwardLinkT *link = tok->links; link != NULL; link = link->next) {

if (link->ilabel == 0) {

// We only need to consider epsilon links, since non-epsilon links

// transition between frames and this function only needs to sort a list

// of tokens from a single frame.

IterType following_iter = token2pos.find(link->next_tok);

if (following_iter != token2pos.end()) { // another token on this frame,

// so must consider it.

int32 next_pos = following_iter->second;

if (next_pos < pos) { // reassign the position of the next Token.

following_iter->second = cur_pos++;

reprocess.insert(link->next_tok);

}

}

}

}

// In case we had previously assigned this token to be reprocessed, we can

// erase it from that set because it's "happy now" (we just processed it).

reprocess.erase(tok);

}

size_t max_loop = 1000000, loop_count; // max_loop is to detect epsilon cycles.

for (loop_count = 0;

!reprocess.empty() && loop_count < max_loop; ++loop_count) {

std::vector<Token*> reprocess_vec;

for (typename unordered_set<Token*>::iterator iter = reprocess.begin();

iter != reprocess.end(); ++iter)

reprocess_vec.push_back(*iter);

reprocess.clear();

for (typename std::vector<Token*>::iterator iter = reprocess_vec.begin();

iter != reprocess_vec.end(); ++iter) {

Token *tok = *iter;

int32 pos = token2pos[tok];

// Repeat the processing we did above (for comments, see above).

for (ForwardLinkT *link = tok->links; link != NULL; link = link->next) {

if (link->ilabel == 0) {

IterType following_iter = token2pos.find(link->next_tok);

if (following_iter != token2pos.end()) {

int32 next_pos = following_iter->second;

if (next_pos < pos) {

following_iter->second = cur_pos++;

reprocess.insert(link->next_tok);

}

}

}

}

}

}

KALDI_ASSERT(loop_count < max_loop && "Epsilon loops exist in your decoding "

"graph (this is not allowed!)");