filter-pt.cpp.svn-base

来自「moses开源的机器翻译系统」· SVN-BASE 代码 · 共 360 行

#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <algorithm>

#include "_SuffixArraySearchApplicationBase.h"

#include <vector>
#include <iostream>
#include <set>

#ifdef WIN32
#include "WIN32_functions.h"
#else
#include <unistd.h>
#endif

typedef std::set<TextLenType> SentIdSet;
typedef std::map<std::string, SentIdSet> PhraseSetMap;

#undef min

// constants
const size_t MINIMUM_SIZE_TO_KEEP = 10000;     // reduce this to improve memory usage,
                                               // increase for speed
const std::string SEPARATOR       = " ||| ";

const double ALPHA_PLUS_EPS  = -1000.0;        // dummy value
const double ALPHA_MINUS_EPS = -2000.0;        // dummy value

// configuration params
int pfe_filter_limit = 0;               // 0 = don't filter anything based on P(f|e)
bool print_cooc_counts = false;         // add cooc counts to phrase table?
bool print_neglog_significance = false; // add -log(p) to phrase table?
double sig_filter_limit = 0;            // keep phrase pairs with -log(sig) > sig_filter_limit
                                        //    higher = filter-more
bool pef_filter_only = false;           // only filter based on pef

// globals
PhraseSetMap esets;
double p_111 = 0.0;                     // alpha
size_t nremoved_sigfilter = 0;
size_t nremoved_pfefilter = 0;

C_SuffixArraySearchApplicationBase e_sa;
C_SuffixArraySearchApplicationBase f_sa;
int num_lines;

void usage()
{
    std::cerr << "\nFilter phrase table using significance testing as described\n"
              << "in H. Johnson, et al. (2007) Improving Translation Quality\n"
	      << "by Discarding Most of the Phrasetable. EMNLP 2007.\n"
        << "\nUsage:\n"
        << "\n  filter-pt -e english.suf-arr -f french.suf-arr\n"
	<< "      [-c] [-p] [-l threshold] [-n num] < PHRASE-TABLE > FILTERED-PHRASE-TABLE\n\n"
	<< "   [-l threshold] >0.0, a+e, or a-e: keep values that have a -log significance > this\n"
	<< "   [-n num      ] 0, 1...: 0=no filtering, >0 sort by P(e|f) and keep the top num elements\n"
	<< "   [-c          ] add the cooccurence counts to the phrase table\n"
	<< "   [-p          ] add -log(significance) to the phrasetable\n\n";
    exit(1);
}

struct PTEntry {
    PTEntry(const std::string& str, int index);
    std::string f_phrase;
    std::string e_phrase;
    std::string extra;
    std::string scores;
    float pfe;
    int cf;
    int ce;
    int cfe;
    float nlog_pte;
    void set_cooc_stats(int _cef, int _cf, int _ce, float nlp) {
      cfe = _cef;
      cf = _cf;
      ce = _ce;
      nlog_pte = nlp;
    }
    
};

PTEntry::PTEntry(const std::string& str, int index) :
 cf(0), ce(0), cfe(0), nlog_pte(0.0)
{
    size_t pos = 0;
    std::string::size_type nextPos = str.find(SEPARATOR, pos);
    this->f_phrase = str.substr(pos,nextPos); pos = nextPos + SEPARATOR.size();
    nextPos = str.find(SEPARATOR, pos);
    this->e_phrase = str.substr(pos,nextPos-pos); pos = nextPos + SEPARATOR.size();
    nextPos = str.rfind(SEPARATOR);
    this->extra = str.substr(pos, ((nextPos > pos)?(nextPos-pos):0));
    this->scores = str.substr(nextPos + SEPARATOR.size(),std::string::npos);
    int c = 0;
    std::string::iterator i=scores.begin();
    if (index > 0) {
        for (; i != scores.end(); ++i) {
            if ((*i) == ' ') {
                c++;
                if (c == index) break;
            }
        }
    }
    ++i;
    char f[24];
    char *fp=f;
    while (i != scores.end() && *i != ' ') {
      *fp++=*i++;
    }
    *fp++=0;
    
		this->pfe = atof(f);

    // std::cerr << "L: " << f_phrase << " ::: " << e_phrase << " ::: " << scores << " ::: " << pfe << std::endl;
    // std::cerr << "X: " << extra << "\n"; 
}

struct PfeComparer {
  bool operator()(const PTEntry* a, const PTEntry* b) const { return a->pfe > b->pfe; }
};

struct NlogSigThresholder {
  NlogSigThresholder(float threshold) : t(threshold) {}
  float t;
  bool operator()(const PTEntry* a) const { if (a->nlog_pte < t) { delete a; return true; } else return false; }
};

std::ostream& operator << (std::ostream& os, const PTEntry& pp)
{
  os << pp.f_phrase << " ||| " << pp.e_phrase;
  if (pp.extra.size()>0) os << " ||| " << pp.extra;
  os << " ||| " << pp.scores;
  if (print_cooc_counts) os << " ||| " << pp.cfe << " " << pp.cf << " " << pp.ce;
  if (print_neglog_significance) os << " ||| " << pp.nlog_pte;
  return os;
}

void print(int a, int b, int c, int d, float p) {
  std::cerr << a << "\t" << b << "\t P=" << p << "\n"
            << c << "\t" << d << "\t xf=" << (double)(b)*(double)(c)/(double)(a+1)/(double)(d+1) << "\n\n";
}

// 2x2 (one-sided) Fisher's exact test
// see B. Moore. (2004) On Log Likelihood and the Significance of Rare Events
double fisher_exact(int cfe, int ce, int cf)
{
    assert(cfe <= ce);
    assert(cfe <= cf);

    int a = cfe;
    int b = (cf - cfe);
    int c = (ce - cfe);
    int d = (num_lines - ce - cf + cfe);
    int n = a + b + c + d;

    double cp = exp(lgamma(1+a+c) + lgamma(1+b+d) + lgamma(1+a+b) + lgamma(1+c+d) - lgamma(1+n) - lgamma(1+a) - lgamma(1+b) - lgamma(1+c) - lgamma(1+d));
    double total_p = 0.0;
    int tc = std::min(b,c);
    for (int i=0; i<=tc; i++) {
      total_p += cp;
//      double lg = lgamma(1+a+c) + lgamma(1+b+d) + lgamma(1+a+b) + lgamma(1+c+d) - lgamma(1+n) - lgamma(1+a) - lgamma(1+b) - lgamma(1+c) - lgamma(1+d); double cp = exp(lg);
//      print(a,b,c,d,cp);
      double coef = (double)(b)*(double)(c)/(double)(a+1)/(double)(d+1);
      cp *= coef;
      ++a; --c; ++d; --b;
    }
  return total_p;
}

// input: unordered list of translation options for a single source phrase
void compute_cooc_stats_and_filter(std::vector<PTEntry*>& options)
{
  if (pfe_filter_limit>0 && options.size() > pfe_filter_limit) {
    nremoved_pfefilter += (options.size() - pfe_filter_limit);
    std::nth_element(options.begin(), options.begin()+pfe_filter_limit, options.end(), PfeComparer());
    for (std::vector<PTEntry*>::iterator i=options.begin()+pfe_filter_limit; i != options.end(); ++i)
      delete *i;
    options.erase(options.begin()+pfe_filter_limit,options.end());
  }
  if (pef_filter_only) return;
  
  SentIdSet fset;
  vector<S_SimplePhraseLocationElement> locations;
  //std::cerr << "Looking up f-phrase: " << options.front()->f_phrase << "\n";

  locations = f_sa.locateExactPhraseInCorpus(options.front()->f_phrase.c_str());
  if(locations.size()==0){
	  cerr<<"No occurrences found!!\n";
  }
  for (vector<S_SimplePhraseLocationElement>::iterator i=locations.begin();
		  i != locations.end();
		  ++i)
  {
	  fset.insert(i->sentIdInCorpus);
  }
  size_t cf = fset.size();
  for (std::vector<PTEntry*>::iterator i=options.begin(); i != options.end(); ++i) {
    const std::string& e_phrase = (*i)->e_phrase;
    size_t cef=0;
    SentIdSet& eset = esets[(*i)->e_phrase];
    if (eset.empty()) {
      //std::cerr << "Looking up e-phrase: " << e_phrase << "\n";  
      vector<S_SimplePhraseLocationElement> locations = e_sa.locateExactPhraseInCorpus(e_phrase.c_str());
      for (vector<S_SimplePhraseLocationElement>::iterator i=locations.begin(); i!= locations.end(); ++i) {
          TextLenType curSentId = i->sentIdInCorpus;
  	  eset.insert(curSentId);
      }
    }
    size_t ce=eset.size();
    if (ce < cf) {
      for (SentIdSet::iterator i=eset.begin(); i != eset.end(); ++i) {
        if (fset.find(*i) != fset.end()) cef++;
      }
    } else {
      for (SentIdSet::iterator i=fset.begin(); i != fset.end(); ++i) {
        if (eset.find(*i) != eset.end()) cef++;
      }
    }
    double nlp = -log(fisher_exact(cef, cf, ce));
    (*i)->set_cooc_stats(cef, cf, ce, nlp);
    if (ce < MINIMUM_SIZE_TO_KEEP) {
      esets.erase(e_phrase);
    }
  }
  std::vector<PTEntry*>::iterator new_end = 
    std::remove_if(options.begin(), options.end(), NlogSigThresholder(sig_filter_limit));
  nremoved_sigfilter += (options.end() - new_end);
  options.erase(new_end,options.end());
}

int main(int argc, char * argv[]){
    int c;
    const char* efile=0;
    const char* ffile=0;
    int pfe_index = 2;
    while ((c = getopt(argc, argv, "cpf:e:i:n:l:")) != -1) {
        switch (c) {
            case 'e':
                efile = optarg;
                break;
            case 'f':
                ffile = optarg;
                break;
            case 'i':  // index of pfe in phrase table
                pfe_index = atoi(optarg);
                break;
            case 'n':  // keep only the top n entries in phrase table sorted by p(f|e) (0=all)
                pfe_filter_limit = atoi(optarg);
		std::cerr << "P(f|e) filter limit: " << pfe_filter_limit << std::endl;
                break;
	    case 'c':
	    	print_cooc_counts = true;
	    	break;
	    case 'p':
	    	print_neglog_significance = true;
	    	break;
	    case 'l':
	        std::cerr << "-l = " << optarg << "\n";
	        if (strcmp(optarg,"a+e") == 0) {
		  sig_filter_limit = ALPHA_PLUS_EPS;
		} else if (strcmp(optarg,"a-e") == 0) {
		  sig_filter_limit = ALPHA_MINUS_EPS;
		} else {
		  char *x;
		  sig_filter_limit = strtod(optarg, &x);
		  if (sig_filter_limit < 0.0) {
		    std::cerr << "Filter limit (-l) must be either 'a+e', 'a-e' or a real number >= 0.0\n";
		    usage();
		  }
		}
	    	break;
            default:
                usage();
        }
    }
    if (sig_filter_limit == 0.0) pef_filter_only = true;
    //-----------------------------------------------------------------------------	
    if (optind != argc || ((!efile || !ffile) && !pef_filter_only)) {
      usage();
    }

    //load the indexed corpus with vocabulary(noVoc=false) and with offset(noOffset=false)
    if (!pef_filter_only) {
      e_sa.loadData_forSearch(efile, false, false);
      f_sa.loadData_forSearch(ffile, false, false);
      size_t elines = e_sa.returnTotalSentNumber();
      size_t flines = f_sa.returnTotalSentNumber();
      if (elines != flines) {
        std::cerr << "Number of lines in e-corpus != number of lines in f-corpus!\n";
        usage();
      } else {
        std::cerr << "Training corpus: " << elines << " lines\n";
        num_lines = elines;
      }
      p_111 = -log(fisher_exact(1,1,1));
      std::cerr << "\\alpha = " << p_111 << "\n";
      if (sig_filter_limit == ALPHA_MINUS_EPS) { sig_filter_limit = p_111 - 0.001; }
        else if (sig_filter_limit == ALPHA_PLUS_EPS) { sig_filter_limit = p_111 + 0.001; }
      std::cerr << "Sig filter threshold is = " << sig_filter_limit << "\n";
    } else {
      std::cerr << "Filtering using P(e|f) only. n=" << pfe_filter_limit << std::endl;
    }

    char tmpString[10000];
    std::string prev = "";
    std::vector<PTEntry*> options;
    size_t pt_lines = 0;
    while(!cin.eof()){
	cin.getline(tmpString,10000,'\n');
	if(++pt_lines%10000==0)
	{
	    std::cerr << ".";
	    if(pt_lines%500000==0) std::cerr << "[n:"<<pt_lines<<"]\n";
	}

	if(strlen(tmpString)>0){
            PTEntry* pp = new PTEntry(tmpString, pfe_index);
            if (prev != pp->f_phrase) {
                prev = pp->f_phrase;

		if (!options.empty()) {  // always true after first line
		  compute_cooc_stats_and_filter(options);
		}
		for (std::vector<PTEntry*>::iterator i=options.begin(); i != options.end(); ++i) {
			std::cout << **i << std::endl;
			delete *i;
		}
		options.clear();
		options.push_back(pp);
		
            } else {
	        options.push_back(pp);
	    }
            //			  for(int i=0;i<locations.size(); i++){
            //				  cout<<"SentId="<<locations[i].sentIdInCorpus<<" Pos="<<(int)locations[i].posInSentInCorpus<<endl;
            //			  }
        }
    }
    compute_cooc_stats_and_filter(options);
    for (std::vector<PTEntry*>::iterator i=options.begin(); i != options.end(); ++i) {
        std::cout << **i << std::endl;
        delete *i;
    }
    float pfefper = (100.0*(float)nremoved_pfefilter)/(float)pt_lines;
    float sigfper = (100.0*(float)nremoved_sigfilter)/(float)pt_lines;
    std::cerr << "\n\n------------------------------------------------------\n"
              << "  unfiltered phrases pairs: " << pt_lines << "\n"
              << "\n"
	      << "     P(f|e) filter [first]: " << nremoved_pfefilter << "   (" << pfefper << "%)\n"
	      << "       significance filter: " << nremoved_sigfilter << "   (" << sigfper << "%)\n"
	      << "            TOTAL FILTERED: " << (nremoved_pfefilter + nremoved_sigfilter) << "   (" << (sigfper + pfefper) << "%)\n"
              << "\n"
              << "     FILTERED phrase pairs: " << (pt_lines - nremoved_pfefilter - nremoved_sigfilter) << "   (" << (100.0-sigfper - pfefper) << "%)\n"
	      << "------------------------------------------------------\n";
	      
    return 0;
}