/* 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(a).set(j,new_i); LogProb b_prob=prob_of_target_and_alignment_given_source(a,2); const_cast(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(a).set(j1,aj2); const_cast(a).set(j2,aj1); LogProb b_prob=prob_of_target_and_alignment_given_source(a,2); const_cast(a).set(j1,aj1); const_cast(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&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 }