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Diffstat (limited to 'mgizapp/src/transpair_model4.cpp')
| -rw-r--r-- | mgizapp/src/transpair_model4.cpp | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/mgizapp/src/transpair_model4.cpp b/mgizapp/src/transpair_model4.cpp new file mode 100644 index 0000000..ebc2666 --- /dev/null +++ b/mgizapp/src/transpair_model4.cpp @@ -0,0 +1,179 @@ +/* + +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 +} |