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viterbi_main.cc
/*************************************************************************/
/* */
/* Centre for Speech Technology Research */
/* University of Edinburgh, UK */
/* Copyright (c) 1995,1996 */
/* All Rights Reserved. */
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/* Permission is hereby granted, free of charge, to use and distribute */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* permit persons to whom this work is furnished to do so, subject to */
/* the following conditions: */
/* 1. The code must retain the above copyright notice, this list of */
/* conditions and the following disclaimer. */
/* 2. Any modifications must be clearly marked as such. */
/* 3. Original authors' names are not deleted. */
/* 4. The authors' names are not used to endorse or promote products */
/* derived from this software without specific prior written */
/* permission. */
/* */
/* THE UNIVERSITY OF EDINBURGH AND THE CONTRIBUTORS TO THIS WORK */
/* DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING */
/* ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT */
/* SHALL THE UNIVERSITY OF EDINBURGH NOR THE CONTRIBUTORS BE LIABLE */
/* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES */
/* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN */
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/* ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF */
/* THIS SOFTWARE. */
/* */
/*************************************************************************/
/* Authors: Alan W Black and Simon King */
/* Date : January 1997 */
/*-----------------------------------------------------------------------*/
/* A simple use of the Viterbi decoder */
/* */
/*=======================================================================*/
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include "EST.h"
EST_read_status load_TList_of_StrVector(EST_TList<EST_StrVector> &w,
const EST_String &filename,
const int vec_len);
static void print_results(EST_Relation &wstream);
static bool do_search(EST_Relation &wstream);
static EST_VTPath *vit_npath(EST_VTPath *p,EST_VTCandidate *c,EST_Features &f);
static EST_VTCandidate *vit_candlist(EST_Item *s,EST_Features &f);
static void top_n_candidates(EST_VTCandidate* &all_c);
static void load_vocab(const EST_String &vfile);
static void add_word(EST_Relation &w, const EST_String &word, int pos);
static void load_wstream(const EST_String &filename,
const EST_String &vfile,
EST_Relation &w,
EST_Track &obs);
static void load_given(const EST_String &filename,
const int ngram_order);
static double find_gram_prob(EST_VTPath *p,int *state);
// special stuff for non-sliding window ngrams
static double find_extra_gram_prob(EST_VTPath *p,int *state, int time);
static void get_history(EST_StrVector &history, EST_VTPath *p);
static void fill_window(EST_StrVector &window,EST_StrVector &history,
EST_VTPath *p,const int time);
static int is_a_special(const EST_String &s, int &val);
static int max_history=0;
static EST_Ngrammar ngram;
static EST_String pstring = SENTENCE_START_MARKER;
static EST_String ppstring = SENTENCE_END_MARKER;
static float lm_scale = 1.0;
static float ob_scale = 1.0;
static float ob_scale2 = 1.0;
// pruning beam widths
static float beam=-1;
static float ob_beam=-1;
static int n_beam = -1;
static bool trace_on = FALSE;
// always logs
static double ob_log_prob_floor = SAFE_LOG_ZERO;
static double ob_log_prob_floor2 = SAFE_LOG_ZERO;
static double lm_log_prob_floor = SAFE_LOG_ZERO;
int btest_debug = FALSE;
static EST_String out_file = "";
static EST_StrList vocab;
static EST_Track observations;
static EST_Track observations2;
static EST_TList<EST_StrVector> given; // to do : convert to array for speed
int using_given=FALSE;
// default is that obs are already logs
int take_logs = FALSE;
int num_obs = 1;
/** @name <command>viterbi</command> <emphasis>Combine n-gram model and likelihoods to estimate posterior probabilities</emphasis>
* @id viterbi-manual
* @toc
*/
//@{
/**@name Synopsis
*/
//@{
//@synopsis
/**
viterbi is a simple time-synchronous Viterbi decoder. It finds the
most likely sequence of items drawn from a fixed vocabulary, given
frame-by-frame observation probabilities for each item in that
vocabulary, and a ngram grammar. Possible uses include:
<itemizedlist>
<listitem><para>Simple speech recogniser back end</para></listitem>
</itemizedlist>
viterbi can optionally use two sets of frame-by-frame observation
probabilities in a weighted-sum fashion. Also, the ngram language model
is not restricted to the conventional sliding window type in which the
previous n-1 items are the ngram context. Items in the ngram context
at each frame may be given. In this case, the user must provide a file
containing the ngram context: one (n-1) tuple per line. To include
items from the partial Viterbi path so far (i.e. found at recognition
time, not given) the special notation <-N> is used where N indicates
the distance back to the item required. For example <-1> would
indicate the item on the partial Viterbi path at the last frame. See
\Ref{Examples}.
<formalpara>
<para><title>Pruning</title></para>
<para>
Three types of pruning are available to reduce the size of the search
space and therefore speed up the search:
<itemizedlist>
<listitem><para>Observation pruning</para></listitem>
<listitem><para>Top-N pruning at each frame</para></listitem>
<listitem><para>Fixed width beam pruning</para></listitem>
</itemizedlist>
</para>
</formalpara>
*/
//@}
/**@name Options
*/
//@{
//@options
//@}
int main(int argc, char **argv)
{
EST_StrList files;
EST_Option al;
EST_Relation wstream;
double floor; // a temporary
parse_command_line(argc, argv,
EST_String("[observations file] -o [output file]\n")+
"Summary: find the most likely path through a sequence of\n"+
" observations, constrained by a language model.\n"+
"-ngram <string> Grammar file, required\n"+
"-given <string> ngram left contexts, per frame\n"+
"-vocab <string> File with names of vocabulary, this\n"+
" must be same number as width of observations, required\n"+
"-ob_type <string> Observation type : likelihood .... and change doc\"probs\" or \"logs\" (default is \"logs\")\n"+
"\nFloor values and scaling (scaling is applied after floor value)\n"+
"-lm_floor <float> LM floor probability\n"+
"-lm_scale <float> LM scale factor factor (applied to log prob)\n"+
"-ob_floor <float> Observations floor probability\n"+
"-ob_scale <float> Observation scale factor (applied to prob or log prob, depending on -ob_type)\n\n"+
"-prev_tag <string>\n"+
" tag before sentence start\n"+
"-prev_prev_tag <string>\n"+
" all words before 'prev_tag'\n"+
"-last_tag <string>\n"+
" after sentence end\n"+
"-default_tags use default tags of "+SENTENCE_START_MARKER+","
SENTENCE_END_MARKER+" and "+SENTENCE_END_MARKER+"\n"+
" respectively\n\n"+
"-observes2 <string> second observations (overlays first, ob_type must be same)\n"+
"-ob_floor2 <float> \n"+
"-ob_scale2 <float> \n\n"+
"-ob_prune <float> observation pruning beam width (log) probability\n"+
"-n_prune <int> top-n pruning of observations\n"+
"-prune <float> pruning beam width (log) probability\n"+
"-trace show details of search as it proceeds\n",
files, al);
out_file = al.present("-o") ? al.val("-o") : (EST_String)"-";
if (files.length() != 1)
{
cerr << argv[0];
cerr << ": you must give exactly one observations file on the command line";
cerr << endl;
cerr << "(use -observes2 for optional second observations)" << endl;
exit(-1);
}
if (al.present("-ngram"))
{
ngram.load(al.val("-ngram"));
}
else
{
cerr << argv[0] << ": no ngram specified" << endl;
exit(-1);
}
if(!al.present("-vocab"))
{
cerr << "You must provide a vocabulary file !" << endl;
exit(-1);
}
load_wstream(files.first(),al.val("-vocab"),wstream,observations);
if (al.present("-observes2"))
{
load_wstream(al.val("-observes2"),al.val("-vocab"),wstream,observations2);
num_obs = 2;
}
if (al.present("-given"))
{
load_given(al.val("-given"),ngram.order());
using_given=TRUE;
}
if (al.present("-lm_scale"))
lm_scale = al.fval("-lm_scale");
else
lm_scale = 1.0;
if (al.present("-ob_scale"))
ob_scale = al.fval("-ob_scale");
else
ob_scale = 1.0;
if (al.present("-ob_scale2"))
ob_scale2 = al.fval("-ob_scale2");
else
ob_scale2 = 1.0;
if (al.present("-prev_tag"))
pstring = al.val("-prev_tag");
if (al.present("-prev_prev_tag"))
ppstring = al.val("-prev_prev_tag");
// pruning
if (al.present("-prune"))
beam = al.fval("-prune");
else
beam = -1; // no pruning
if (al.present("-ob_prune"))
ob_beam = al.fval("-ob_prune");
else
ob_beam = -1; // no pruning
if (al.present("-n_prune"))
{
n_beam = al.ival("-n_prune");
if(n_beam <= 0)
{
cerr << "WARNING : " << n_beam;
cerr << " is not a reasonable value for -n_prune !" << endl;
}
}
else
n_beam = -1; // no pruning
if (al.present("-trace"))
trace_on = TRUE;
// language model floor
if (al.present("-lm_floor"))
{
floor = al.fval("-lm_floor");
if(floor < 0)
{
cerr << "Error : LM floor probability is negative !" << endl;
exit(-1);
}
else if(floor > 1)
{
cerr << "Error : LM floor probability > 1 " << endl;
exit(-1);
}
lm_log_prob_floor = safe_log(floor);
}
// observations floor
if (al.present("-ob_floor"))
{
floor = al.fval("-ob_floor");
if(floor < 0)
{
cerr << "Error : Observation floor probability is negative !" << endl;
exit(-1);
}
else if(floor > 1)
{
cerr << "Error : Observation floor probability > 1 " << endl;
exit(-1);
}
ob_log_prob_floor = safe_log(floor);
}
if (al.present("-ob_floor2"))
{
floor = al.fval("-ob_floor2");
if(floor < 0)
{
cerr << "Error : Observation2 floor probability is negative !" << endl;
exit(-1);
}
else if(floor > 1)
{
cerr << "Error : Observation2 floor probability > 1 " << endl;
exit(-1);
}
ob_log_prob_floor2 = safe_log(floor);
}
if (al.present("-ob_type"))
{
if(al.val("-ob_type") == "logs")
take_logs = false;
else if(al.val("-ob_type") == "probs")
take_logs = true;
else
{
cerr << "\"" << al.val("-ob_type")
<< "\" is not a valid ob_type : try \"logs\" or \"probs\"" << endl;
exit(-1);
}
}
if(do_search(wstream))
print_results(wstream);
else
cerr << "No path could be found." << endl;
return 0;
}
static void print_results(EST_Relation &wstream)
{
EST_Item *s;
float pscore;
EST_String predict;
FILE *fd;
if (out_file == "-")
fd = stdout;
else if ((fd = fopen(out_file,"wb")) == NULL)
{
cerr << "can't open \"" << out_file << "\" for output" << endl;
exit(-1);
}
for (s=wstream.head(); s != 0 ; s=inext(s))
{
predict = s->f("best").string();
pscore = s->f("best_score");
fprintf(fd,"%s %f\n",(const char *)predict,pscore);
}
if (out_file != "")
fclose(fd);
}
static bool do_search(EST_Relation &wstream)
{
// Apply Ngram to matrix of probs
int states;
states = ngram.num_states();
EST_Viterbi_Decoder vc(vit_candlist,vit_npath,states);
vc.initialise(&wstream);
if((beam > 0) || (ob_beam > 0))
vc.set_pruning_parameters(beam,ob_beam);
if(trace_on)
{
vc.turn_on_trace();
cerr << "Starting Viterbi search..." << endl;
}
vc.search();
return vc.result("best"); // adds fields to w with best values
}
static void load_wstream(const EST_String &filename,
const EST_String &vfile,
EST_Relation &w,
EST_Track &obs)
{
// Load in vocab and probs into Stream (this isn't general)
EST_String word, pos;
int i=-1;
if(vocab.empty())
load_vocab(vfile);
if (obs.load(filename,0.10) != 0)
{
cerr << "can't find observations file \"" << filename << "\"" << endl;
exit(-1);
}
if (vocab.length() != obs.num_channels())
{
cerr << "Number in vocab (" << vocab.length() <<
") not equal to observation's width (" <<
obs.num_channels() << ")" << endl;
exit(-1);
}
if(w.empty())
{
for (i=0; i < obs.num_frames(); i++)
{
add_word(w,itoString(i),i);
}
}
}
static void load_given(const EST_String &filename,
const int ngram_order)
{
EST_String word, pos;
EST_Litem *p;
int i,j;
if (load_TList_of_StrVector(given,filename,ngram_order-1) != 0)
{
cerr << "can't load given file \"" << filename << "\"" << endl;
exit(-1);
}
// set max history
for (p = given.head(); p; p = p->next())
{
for(i=0;i<given(p).length();i++)
if( is_a_special( given(p)(i), j) && (-j > max_history))
max_history = -j;
}
}
static void load_vocab(const EST_String &vfile)
{
// Load vocabulary (strings)
EST_TokenStream ts;
if (ts.open(vfile) == -1)
{
cerr << "can't find vocab file \"" << vfile << "\"" << endl;
exit(-1);
}
while (!ts.eof())
{
if (ts.peek() != "")
{
vocab.append(ts.get().string());
}
}
ts.close();
}
static void add_word(EST_Relation &w, const EST_String &word, int pos)
{
EST_Item *item = w.append();
item->set_name(word);
item->set("pos",pos);
}
static EST_VTCandidate *vit_candlist(EST_Item *s,EST_Features &f)
{
// Return a list of new candidates from this point
double prob=1.0,prob2=1.0;
int i;
EST_Litem *p;
int observe;
EST_VTCandidate *all_c = 0;
EST_VTCandidate *c;
(void)f;
observe = s->f("pos"); // index for observations TRACK
for (i=0,p=vocab.head(); i < observations.num_channels(); i++,p=p->next())
{
c = new EST_VTCandidate;
c->name = vocab(p); // to be more efficient this could be the index
prob = observations.a(observe,i);
if(num_obs == 2)
prob2 = observations2.a(observe,i);
if(take_logs)
{
prob = safe_log10(prob);
if (prob < ob_log_prob_floor)
prob = ob_log_prob_floor;
if(num_obs == 2)
{
prob2 = safe_log10(prob2);
if (prob2 < ob_log_prob_floor2)
prob2 = ob_log_prob_floor2;
}
}
else // already in logs
{
if (prob < ob_log_prob_floor)
prob = ob_log_prob_floor;
if ((num_obs == 2) && (prob2 < ob_log_prob_floor2))
prob2 = ob_log_prob_floor2;
}
prob *= ob_scale;
prob2 *= ob_scale2;
if(num_obs == 2)
c->score = prob + prob2;
else
c->score = prob;
c->next = all_c;
c->s = s;
all_c = c;
}
if(n_beam > 0)
{
// N.B. this might be very time-consuming
top_n_candidates(all_c);
}
return all_c;
}
static EST_VTPath *vit_npath(EST_VTPath *p,EST_VTCandidate *c,
EST_Features &f)
{
// Build a (potential) new path link from this previous path and
// This candidate
EST_VTPath *np = new EST_VTPath;
double lprob,prob;
EST_String prev,ttt;
(void)f;
np->c = c;
np->from = p;
// are we using extra info ?
if(using_given)
// time of candidate is
// c->s->f("pos");
prob = find_extra_gram_prob(np,&np->state,c->s->f("pos"));
else
prob = find_gram_prob(np,&np->state);
lprob = safe_log10(prob);
if (lprob < lm_log_prob_floor)
lprob = lm_log_prob_floor;
lprob *= lm_scale;
np->f.set("lscore",(c->score+lprob)); // simonk : changed prob to lprob
if (p==0)
np->score = (c->score+lprob);
else
np->score = (c->score+lprob) + p->score;
return np;
}
static double find_gram_prob(EST_VTPath *p,int *state)
{
// Look up transition probability from *state for name.
// Return probability and update state
double prob=0.0,nprob;
int i,f=FALSE;
EST_VTPath *pp;
EST_StrVector window(ngram.order());
for (pp=p->from,i=ngram.order()-2; i >= 0; i--)
{
if (pp != 0)
{
window[i] = pp->c->name.string();
pp = pp->from;
}
else if (f)
window[i] = ppstring;
else
{
window[i] = pstring;
f = TRUE;
}
}
window[ngram.order()-1] = p->c->name.string();
const EST_DiscreteProbDistribution &pd = ngram.prob_dist(window);
if (pd.samples() == 0)
prob = 0;
else
prob = (double)pd.probability(p->c->name.string());
for (i=0; i < ngram.order()-1; i++)
window[i] = window(i+1);
ngram.predict(window,&nprob,state);
return prob;
}
static double find_extra_gram_prob(EST_VTPath *p,int *state,int time)
{
int i;
double prob=0.0,nprob;
EST_StrVector window(ngram.order());
EST_StrVector history(max_history);
get_history(history,p);
fill_window(window,history,p,time);
/*
cerr << "Looking up ngram ";
for(i=0;i<window.num_points();i++)
cerr << window(i) << " ";
cerr << endl;
*/
const EST_DiscreteProbDistribution &pd = ngram.prob_dist(window);
if (pd.samples() == 0)
prob = 0;
else
prob = (double)pd.probability(p->c->name.string());
// shift history, adding latest item at 'end' (0)
if(max_history>0)
{
for(i=history.length()-1;i>0;i--)
history[i] = history(i-1);
history[0] = p->c->name.string();
}
fill_window(window,history,p,time+1);
ngram.predict(window,&nprob,state);
//cerr << endl << endl;
return prob;
}
static void get_history(EST_StrVector &history, EST_VTPath *p)
{
EST_VTPath *pp;
int i,f=FALSE;
for (pp=p->from,i=0; i < history.length(); i++)
{
if (pp != 0)
{
history[i] = pp->c->name.string();
pp = pp->from;
}
else if (f)
history[i] = ppstring;
else
{
history[i] = pstring;
f = TRUE;
}
}
}
static void fill_window(EST_StrVector &window,EST_StrVector &history,
EST_VTPath *p,const int time)
{
// Look up transition probability from *state for name.
// Return probability and update state
int i,j;
EST_String s;
// can we even do it?
if( time >= given.length() )
return;
// format should be run-time defined, but try this for now
// first n-1 things in window come from 'given'
// last one is predictee
// also want vocab and grammar mismatch allowed !!!!!!
// predictee
window[ngram.order()-1] = p->c->name.string();
// given info for this time
EST_StrVector *this_g = &(given.nth(time)); // inefficient to count down a list
for(i=0;i<ngram.order()-1;i++)
{
if( is_a_special( (*this_g)(i), j))
window[i] = history(-1-j); // j=-1 -> (0) j=-2 -> (1) etc.
else
window[i] = (*this_g)(i);
}
}
static int is_a_special(const EST_String &s, int &val)
{
// special is "<int>"
EST_String tmp;
if(s.contains("<") && s.contains(">"))
{
tmp = s.after("<");
tmp = tmp.before(">");
val = atoi(tmp);
//cerr << "special " << tmp << "=" << val << endl;
return TRUE;
}
return FALSE;
}
static void top_n_candidates(EST_VTCandidate* &all_c)
{
// keep the n most likely candidates
// avoiding a full sort of the (potentially long) list
EST_VTCandidate *top_c=NULL,*p,*q,*this_best, *prev_to_best;
int i;
if(n_beam < 1)
return; // do nothing
// here we assume big is always good
//if(!big_is_good)
//score_multiplier = -1;
for(i=0;i<n_beam;i++)
{
// head of the list is best guess
this_best=all_c;
prev_to_best=NULL;
// find best candidate in all_c
q=NULL;;
for(p=all_c;p!= NULL;q=p,p=p->next)
{
//cerr << "item : " << p->score << endl;
if(p->score > this_best->score)
{
this_best = p;
prev_to_best=q;
}
}
if(this_best == NULL)
break; // give up now - must have run out of candidates
// move best candidate over to new list
if(prev_to_best == NULL)
// best was head of list
all_c = this_best->next;
else
{
// best was not head of all_c
prev_to_best->next = this_best->next;
this_best->next = top_c;
top_c = this_best;
}
}
delete all_c;
all_c = top_c;
/*
cerr << "Here are the top " << n_beam << " candidates" << endl;
for(p=all_c;p != NULL;p=p->next)
cerr << p->score << endl;
*/
}
/**@name Examples
Example 'given' file (items f and g are in the vocabulary), the ngram
is a 4-gram.
<para>
<screen>
<-2> g g
<-1> g f
<-1> f g
<-2> g g
<-3> g g
<-1> g f
</screen>
</para>
*/
//@{
//@}
//@}
EST_DiscreteProbDistribution
Definition EST_simplestats.h:210
EST_DiscreteProbDistribution::samples
double samples(void) const
Total number of example found.
Definition EST_simplestats.h:250
EST_Features
Definition EST_Features.h:62
EST_Features::set
void set(const EST_String &name, int ival)
Definition EST_Features.h:185
EST_Item
Definition EST_Item.h:83
EST_Item::set
void set(const EST_String &name, int ival)
Definition EST_Item.h:179
EST_Ngrammar
Definition EST_Ngrammar.h:209
EST_Option
Definition EST_Option.h:50
EST_Option::fval
float fval(const EST_String &rkey, int m=1) const
Definition EST_Option.cc:98
EST_Option::ival
int ival(const EST_String &rkey, int m=1) const
Definition EST_Option.cc:76
EST_Relation
Definition EST_Relation.h:68
EST_Relation::head
EST_Item * head() const
Definition EST_Relation.h:125
EST_Relation::empty
int empty() const
Definition EST_Relation.h:145
EST_String
Definition EST_String.h:70
EST_String::before
EST_String before(int pos, int len=0) const
Part before position.
Definition EST_String.h:286
EST_String::contains
int contains(const char *s, int pos=-1) const
Does it contain this substring?
Definition EST_String.h:375
EST_String::after
EST_String after(int pos, int len=1) const
Part after pos+len.
Definition EST_String.h:318
EST_TKVL::val
const V & val(const K &rkey, bool m=0) const
return value according to key (const)
Definition EST_TKVL.cc:145
EST_TKVL::present
const int present(const K &rkey) const
Returns true if key is present.
Definition EST_TKVL.cc:222
EST_TList
Definition EST_TList.h:109
EST_TList::first
const T & first() const
return const reference to first item in list
Definition EST_TList.h:146
EST_TVector::length
INLINE int length() const
number of items in vector.
Definition EST_TVector.h:252
EST_TokenStream
Definition EST_Token.h:235
EST_TokenStream::eof
int eof()
end of file
Definition EST_Token.h:356
EST_TokenStream::peek
EST_Token & peek(void)
peek at next token
Definition EST_Token.cc:830
EST_TokenStream::close
void close(void)
Close stream.
Definition EST_Token.cc:406
EST_TokenStream::open
int open(const EST_String &filename)
open a \Ref{EST_TokenStream} for a file.
Definition EST_Token.cc:200
EST_TokenStream::get
EST_TokenStream & get(EST_Token &t)
get next token in stream
Definition EST_Token.cc:486
EST_Track
Definition EST_Track.h:89
EST_Track::load
EST_read_status load(const EST_String name, float ishift=0.0, float startt=0.0)
Definition EST_Track.cc:1309
EST_Track::num_channels
int num_channels() const
return number of channels in track
Definition EST_Track.h:656
EST_Track::num_frames
int num_frames() const
return number of frames in track
Definition EST_Track.h:650
EST_VTCandidate
Definition EST_viterbi.h:58
EST_VTPath
Definition EST_viterbi.h:76
EST_Val::string
const EST_String & string(void) const
Definition EST_Val.h:150