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transpair_model4.cpp
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transpair_model4.cpp
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/*
Copyright (C) 2000,2001 Franz Josef Och (RWTH Aachen - Lehrstuhl fuer Informatik VI)
This file is part of GIZA++ ( extension of GIZA ).
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
USA.
*/
#include "transpair_model4.h"
#include "Parameter.h"
GLOBAL_PARAMETER(float,d4modelsmooth_factor,"model4SmoothFactor","smooting parameter for alignment probabilities in Model 4",PARLEV_SMOOTH,0.2);
LogProb transpair_model4::_scoreOfMove(const alignment&a, WordIndex new_i, WordIndex j,double)const
{
LogProb a_prob=prob_of_target_and_alignment_given_source(a);
alignment b(a);
b.set(j, new_i);
LogProb b_prob=prob_of_target_and_alignment_given_source(b);
if( a_prob )
return b_prob/a_prob;
else if( b_prob )
return 1e20;
else
return 1.0;
}
LogProb transpair_model4::_scoreOfSwap(const alignment&a, WordIndex j1, WordIndex j2,double)const
{
LogProb a_prob=prob_of_target_and_alignment_given_source(a);
alignment b(a);
b.set(j1, a(j2));
b.set(j2, a(j1));
LogProb b_prob=prob_of_target_and_alignment_given_source(b);
if( a_prob )
return b_prob/a_prob;
else if( b_prob )
return 1e20;
else
return 1.0;
}
//increasing efficiency: no copy of alignment (calc. everything incrementally)
LogProb transpair_model4::scoreOfMove(const alignment&a, WordIndex new_i, WordIndex j,double thisValue)const
{
if( a(j)==new_i )
return 1.0;
LogProb change=transpair_model3::scoreOfMove(a,new_i,j,-1.0,0);
LogProb a_prob=thisValue;
if(a_prob<0.0 )
a_prob=prob_of_target_and_alignment_given_source(a,2);
massert(a_prob==prob_of_target_and_alignment_given_source(a,2));
WordIndex old_i=a(j);
//alignment b(a);
const_cast<alignment&>(a).set(j,new_i);
LogProb b_prob=prob_of_target_and_alignment_given_source(a,2);
const_cast<alignment&>(a).set(j,old_i);
change*=b_prob/a_prob;
return change;
}
//increasing efficiency: no copy of alignment (calc. everything incrementally)
LogProb transpair_model4::scoreOfSwap(const alignment&a, WordIndex j1, WordIndex j2,double thisValue)const
{
WordIndex aj1=a(j1),aj2=a(j2);
if( aj1==aj2 )
return 1.0;
LogProb change=transpair_model3::scoreOfSwap(a,j1,j2,-1.0,0);
LogProb a_prob=thisValue;
if( a_prob<0.0 )
a_prob=prob_of_target_and_alignment_given_source(a,2);
massert(a_prob==prob_of_target_and_alignment_given_source(a,2));
//alignment b(a);
const_cast<alignment&>(a).set(j1,aj2);
const_cast<alignment&>(a).set(j2,aj1);
LogProb b_prob=prob_of_target_and_alignment_given_source(a,2);
const_cast<alignment&>(a).set(j1,aj1);
const_cast<alignment&>(a).set(j2,aj2);
if( verboseTP )
cerr << "scoreOfSwap: " << change << ' ' << a_prob << ' ' << b_prob << ' ' << endl;
change*=b_prob/a_prob;
if( verboseTP )
cerr << "resulting: " << change << " should be " << _scoreOfSwap(a,j1,j2) << endl;
return change;
}
LogProb transpair_model4::prob_of_target_and_alignment_given_source_1(const alignment&al,bool verb)const
{
LogProb total = 1.0 ;
total *= pow(double(1-p1), m-2.0 * al.fert(0)) * pow(double(p1), double(al.fert(0)));
if( verb) cerr << "IBM-4: (1-p1)^(m-2 f0)*p1^f0: " << total << endl;
for (WordIndex i = 1 ; i <= al.fert(0) ; i++)
total *= double(m - al.fert(0) - i + 1) / (double(DeficientDistortionForEmptyWord?(max(2,int(m))/DeficientDistortionForEmptyWord):i)) ;
if( verb) cerr << "IBM-4: +NULL:binomial+distortion " << total << endl;
for (WordIndex i = 1 ; i <= l ; i++)
{
total *= get_fertility(i, al.fert(i));// * (LogProb) factorial(al.fert(i));
if( verb) cerr << "IBM-4: fertility of " << i << " " << get_fertility(i, al.fert(i)) << " -> " << total << endl;
}
for (WordIndex j = 1 ; j <= m ; j++)
{
total*= get_t(al(j), j) ;
if( verb) cerr << "IBM-4: t of j:" << j << " i:" << al(j) << ": " << get_t(al(j), j) << " -> " << total << endl;
}
return total;
}
LogProb transpair_model4::prob_of_target_and_alignment_given_source(const alignment&al, short distortionType,bool verb)const
{
LogProb total = 1.0 ;
static const LogProb almostZero = 1E-299 ;
if( distortionType&1 )
{
total *= prob_of_target_and_alignment_given_source_1(al,verb);
}
if( distortionType&2 )
{
for(WordIndex j=1;j<=m;j++)
if( al(j) )
if( al.get_head(al(j))==j)
{
int ep=al.prev_cept(al(j));
float x2=probFirst[ep](j,al.get_center(ep));
massert(x2<=1.0);
total*=x2;
if( verb) cerr << "IBM-4: d=1 of " << j << ": " << x2 << " -> " << total << endl;
}
else
{
float x2=probSecond(j,al.prev_in_cept(j));
massert(x2<=1.0);
total*=x2;
if( verb) cerr << "IBM-4: d>1 of " << j << ": " << x2 << " -> " << total << endl;
}
}
return total?total:almostZero;
}
void transpair_model4::computeScores(const alignment&al,vector<double>&d)const
{
LogProb total1 = 1.0,total2=1.0,total3=1.0,total4=1.0 ;
total1 *= pow(double(1-p1), m-2.0 * al.fert(0)) * pow(double(p1), double(al.fert(0)));
for (WordIndex i = 1 ; i <= al.fert(0) ; i++)
total1 *= double(m - al.fert(0) - i + 1) / (double(DeficientDistortionForEmptyWord?(max(2,int(m))/DeficientDistortionForEmptyWord):i)) ;
for (WordIndex i = 1 ; i <= l ; i++)
total2 *= get_fertility(i, al.fert(i));// * (LogProb) factorial(al.fert(i));
for (WordIndex j = 1 ; j <= m ; j++)
total3*= get_t(al(j), j) ;
for(WordIndex j=1;j<=m;j++)
if( al(j) )
if( al.get_head(al(j))==j)
{
int ep=al.prev_cept(al(j));
float x2=probFirst[ep](j,al.get_center(ep));
total4*=x2;
}
else
{
float x2=probSecond(j,al.prev_in_cept(j));
total4*=x2;
}
d.push_back(total1);//9
d.push_back(total2);//10
d.push_back(total3);//11
d.push_back(total4);//12
}