int mixture::loadpar(char* ipf)
{
mfstream inp(ipf,ios::in);
if (!inp) {
std::stringstream ss_msg;
ss_msg << "cannot open file: " << ipf;
exit_error(IRSTLM_ERROR_IO, ss_msg.str());
}
cerr << "loading parameters from " << ipf << "\n";
// check compatibility
char header[100];
inp.getline(header,100);
int value1,value2;
sscanf(header,"%d %d",&value1,&value2);
if (value1 != lmsize() || value2 != pmax) {
std::stringstream ss_msg;
ss_msg << "parameter file " << ipf << " is incompatible";
exit_error(IRSTLM_ERROR_DATA, ss_msg.str());
}
for (int i=0; i<=lmsize(); i++)
for (int j=0; j<pmax; j++)
inp.readx(l[i][j],sizeof(double),numslm);
return 1;
}
int mixture::savepar(char* opf)
{
mfstream out(opf,ios::out);
cerr << "saving parameters in " << opf << "\n";
out << lmsize() << " " << pmax << "\n";
for (int i=0; i<=lmsize(); i++)
for (int j=0; j<pmax; j++)
out.writex(l[i][j],sizeof(double),numslm);
return 1;
}
shiftbeta::shiftbeta(char* ngtfile,int depth,int prunefreq,double b,TABLETYPE tt):
mdiadaptlm(ngtfile,depth,tt)
{
cerr << "Creating LM with ShiftBeta smoothing\n";
if (b==-1.0 || (b < 1.0 && b >0.0)) {
beta=new double[lmsize()+1];
for (int l=lmsize(); l>1; l--)
beta[l]=b;
} else {
cerr << "shiftbeta: beta must be < 1.0 and > 0\n";
exit (1);
}
prunethresh=prunefreq;
cerr << "PruneThresh: " << prunethresh << "\n";
};
int mixture::train()
{
double zf;
srand(1333);
genpmap();
if (dub()<dict->size()) {
std::stringstream ss_msg;
ss_msg << "\nERROR: DUB value is too small: the LM will possibly compute wrong probabilities if sub-LMs have different vocabularies!\n";
ss_msg << "This exception should already have been handled before!!!\n";
exit_error(IRSTLM_ERROR_MODEL, ss_msg.str());
}
cerr << "mixlm --> DUB: " << dub() << endl;
for (int i=0; i<numslm; i++) {
cerr << i << " sublm --> DUB: " << sublm[i]->dub() << endl;
cerr << "eventually generate OOV code ";
cerr << sublm[i]->dict->encode(sublm[i]->dict->OOV()) << "\n";
sublm[i]->train();
}
//initialize parameters
for (int i=0; i<=lmsize(); i++) {
l[i]=new double*[pmax];
for (int j=0; j<pmax; j++) {
l[i][j]=new double[numslm];
for (int k=0; k<numslm; k++)
l[i][j][k]=1.0/(double)numslm;
}
}
if (ipfname) {
//load parameters from file
loadpar(ipfname);
} else {
//start training of mixture model
double oldl[pmax][numslm];
char alive[pmax],used[pmax];
int totalive;
ngram ng(sublm[0]->dict);
for (int lev=1; lev<=lmsize(); lev++) {
zf=sublm[0]->zerofreq(lev);
cerr << "Starting training at lev:" << lev << "\n";
for (int i=0; i<pmax; i++) {
alive[i]=1;
used[i]=0;
}
totalive=1;
int iter=0;
while (totalive && (iter < 20) ) {
iter++;
for (int i=0; i<pmax; i++)
if (alive[i])
for (int j=0; j<numslm; j++) {
oldl[i][j]=l[lev][i][j];
l[lev][i][j]=1.0/(double)numslm;
}
sublm[0]->scan(ng,INIT,lev);
while(sublm[0]->scan(ng,CONT,lev)) {
//do not include oov for unigrams
if ((lev==1) && (*ng.wordp(1)==sublm[0]->dict->oovcode()))
continue;
int par=pmap(ng,lev);
used[par]=1;
//controllo se aggiornare il parametro
if (alive[par]) {
double backoff=(lev>1?prob(ng,lev-1):1); //backoff
double denom=0.0;
double* numer = new double[numslm];
double fstar,lambda;
//int cv=(int)floor(zf * (double)ng.freq + rand01());
//int cv=1; //old version of leaving-one-out
int cv=(int)floor(zf * (double)ng.freq)+1;
//int cv=1; //old version of leaving-one-out
//if (lev==3)q
//if (iter>10)
// cout << ng
// << " backoff " << backoff
// << " level " << lev
// << "\n";
for (int i=0; i<numslm; i++) {
//use cv if i=0
sublm[i]->discount(ng,lev,fstar,lambda,(i==0)*(cv));
numer[i]=oldl[par][i]*(fstar + lambda * backoff);
ngram ngslm(sublm[i]->dict);
ngslm.trans(ng);
if ((*ngslm.wordp(1)==sublm[i]->dict->oovcode()) &&
(dict->dub() > sublm[i]->dict->size()))
numer[i]/=(double)(dict->dub() - sublm[i]->dict->size());
denom+=numer[i];
}
for (int i=0; i<numslm; i++) {
l[lev][par][i]+=(ng.freq * (numer[i]/denom));
//if (iter>10)
//cout << ng << " l: " << l[lev][par][i] << "\n";
}
delete []numer;
}
}
//normalize all parameters
totalive=0;
for (int i=0; i<pmax; i++) {
double tot=0;
if (alive[i]) {
for (int j=0; j<numslm; j++) tot+=(l[lev][i][j]);
for (int j=0; j<numslm; j++) l[lev][i][j]/=tot;
//decide if to continue to update
if (!used[i] || (reldist(l[lev][i],oldl[i],numslm)<=0.05))
alive[i]=0;
}
totalive+=alive[i];
}
cerr << "Lev " << lev << " iter " << iter << " tot alive " << totalive << "\n";
}
}
}
if (opfname) savepar(opfname);
return 1;
}
int mshiftbeta::discount(ngram ng_,int size,double& fstar,double& lambda, int cv)
{
ngram ng(dict);
ng.trans(ng_);
//cout << "size :" << size << " " << ng <<"\n";
if (size > 1) {
ngram history=ng;
//singleton pruning only on real counts!!
if (ng.ckhisto(size) && get(history,size,size-1) && (history.freq > cv) &&
((size < 3) || ((history.freq-cv) > prunethresh ))) { // no history pruning with corrected counts!
int suc[3];
suc[0]=succ1(history.link);
suc[1]=succ2(history.link);
suc[2]=history.succ-suc[0]-suc[1];
if (get(ng,size,size) &&
(!prunesingletons() || mfreq(ng,size)>1 || size<3) &&
(!prunetopsingletons() || mfreq(ng,size)>1 || size<maxlevel())) {
ng.freq=mfreq(ng,size);
cv=(cv>ng.freq)?ng.freq:cv;
if (ng.freq>cv) {
double b=(ng.freq-cv>=3?beta[2][size]:beta[ng.freq-cv-1][size]);
fstar=(double)((double)(ng.freq - cv) - b)/(double)(history.freq-cv);
lambda=(beta[0][size] * suc[0] + beta[1][size] * suc[1] + beta[2][size] * suc[2])
/
(double)(history.freq-cv);
if ((size>=3 && prunesingletons()) ||
(size==maxlevel() && prunetopsingletons()))
//correction
lambda+=(double)(suc[0] * (1-beta[0][size])) / (double)(history.freq-cv);
} else {
// ng.freq==cv
ng.freq>=3?suc[2]--:suc[ng.freq-1]--; //update successor stat
fstar=0.0;
lambda=(beta[0][size] * suc[0] + beta[1][size] * suc[1] + beta[2][size] * suc[2])
/
(double)(history.freq-cv);
if ((size>=3 && prunesingletons()) ||
(size==maxlevel() && prunetopsingletons())) //correction
lambda+=(double)(suc[0] * (1-beta[0][size])) / (double)(history.freq-cv);
ng.freq>=3?suc[2]++:suc[ng.freq-1]++; //resume successor stat
}
} else {
fstar=0.0;
lambda=(beta[0][size] * suc[0] + beta[1][size] * suc[1] + beta[2][size] * suc[2])
/
(double)(history.freq-cv);
if ((size>=3 && prunesingletons()) ||
(size==maxlevel() && prunetopsingletons())) //correction
lambda+=(double)(suc[0] * (1-beta[0][size])) / (double)(history.freq-cv);
}
//cerr << "ngram :" << ng << "\n";
if (*ng.wordp(1)==dict->oovcode()) {
lambda+=fstar;
fstar=0.0;
} else {
*ng.wordp(1)=dict->oovcode();
if (get(ng,size,size)) {
ng.freq=mfreq(ng,size);
if ((!prunesingletons() || mfreq(ng,size)>1 || size<3) &&
(!prunetopsingletons() || mfreq(ng,size)>1 || size<maxlevel())) {
double b=(ng.freq>=3?beta[2][size]:beta[ng.freq-1][size]);
lambda+=(double)(ng.freq - b)/(double)(history.freq-cv);
}
}
}
} else {
fstar=0;
lambda=1;
}
} else { // unigram case, no cross-validation
lambda=0.0;
int unigrtotfreq=(size<lmsize()?btotfreq():totfreq());
if (get(ng,size,size))
fstar=(double) mfreq(ng,size)/(double)unigrtotfreq;
else {
cerr << "Missing probability for word: " << dict->decode(*ng.wordp(1)) << "\n";
exit(1);
}
}
return 1;
}
int mshiftbeta::train()
{
trainunigr();
gencorrcounts();
gensuccstat();
ngram ng(dict);
int n1,n2,n3,n4;
int unover3=0;
oovsum=0;
for (int l=1; l<=lmsize(); l++) {
cerr << "level " << l << "\n";
cerr << "computing statistics\n";
n1=0;
n2=0;
n3=0,n4=0;
scan(ng,INIT,l);
while(scan(ng,CONT,l)) {
//skip ngrams containing _OOV
if (l>1 && ng.containsWord(dict->OOV(),l)) {
//cerr << "skp ngram" << ng << "\n";
continue;
}
//skip n-grams containing </s> in context
if (l>1 && ng.containsWord(dict->EoS(),l-1)) {
//cerr << "skp ngram" << ng << "\n";
continue;
}
//skip 1-grams containing <s>
if (l==1 && ng.containsWord(dict->BoS(),l)) {
//cerr << "skp ngram" << ng << "\n";
continue;
}
ng.freq=mfreq(ng,l);
if (ng.freq==1) n1++;
else if (ng.freq==2) n2++;
else if (ng.freq==3) n3++;
else if (ng.freq==4) n4++;
if (l==1 && ng.freq >=3) unover3++;
}
if (l==1) {
cerr << " n1: " << n1 << " n2: " << n2 << " n3: " << n3 << " n4: " << n4 << " unover3: " << unover3 << "\n";
} else {
cerr << " n1: " << n1 << " n2: " << n2 << " n3: " << n3 << " n4: " << n4 << "\n";
}
if (n1 == 0 || n2 == 0 || n1 <= n2) {
cerr << "Error: lower order count-of-counts cannot be estimated properly\n";
cerr << "Hint: use another smoothing method with this corpus.\n";
exit(1);
}
double Y=(double)n1/(double)(n1 + 2 * n2);
beta[0][l] = Y; //equivalent to 1 - 2 * Y * n2 / n1
if (n3 ==0 || n4 == 0 || n2 <= n3 || n3 <= n4 ){
cerr << "Warning: higher order count-of-counts cannot be estimated properly\n";
cerr << "Fixing this problem by resorting only on the lower order count-of-counts\n";
beta[1][l] = Y;
beta[2][l] = Y;
}
else{
beta[1][l] = 2 - 3 * Y * n3 / n2;
beta[2][l] = 3 - 4 * Y * n4 / n3;
}
if (beta[1][l] < 0){
cerr << "Warning: discount coefficient is negative \n";
cerr << "Fixing this problem by setting beta to 0 \n";
beta[1][l] = 0;
}
if (beta[2][l] < 0){
cerr << "Warning: discount coefficient is negative \n";
cerr << "Fixing this problem by setting beta to 0 \n";
beta[2][l] = 0;
}
if (l==1)
oovsum=beta[0][l] * (double) n1 + beta[1][l] * (double)n2 + beta[2][l] * (double)unover3;
cerr << beta[0][l] << " " << beta[1][l] << " " << beta[2][l] << "\n";
}
return 1;
};
int shiftbeta::train()
{
ngram ng(dict);
int n1,n2;
trainunigr();
beta[1]=0.0;
for (int l=2; l<=lmsize(); l++) {
cerr << "level " << l << "\n";
n1=0;
n2=0;
scan(ng,INIT,l);
while(scan(ng,CONT,l)) {
if (l<lmsize()) {
//Computing succ1 statistics for this ngram
//to correct smoothing due to singleton pruning
ngram hg=ng;
get(hg,l,l);
int s1=0;
ngram ng2=hg;
ng2.pushc(0);
succscan(hg,ng2,INIT,l+1);
while(succscan(hg,ng2,CONT,l+1)) {
if (ng2.freq==1) s1++;
}
succ1(hg.link,s1);
}
//skip ngrams containing _OOV
if (l>1 && ng.containsWord(dict->OOV(),l)) {
//cerr << "skp ngram" << ng << "\n";
continue;
}
//skip n-grams containing </s> in context
if (l>1 && ng.containsWord(dict->EoS(),l-1)) {
//cerr << "skp ngram" << ng << "\n";
continue;
}
//skip 1-grams containing <s>
if (l==1 && ng.containsWord(dict->BoS(),l)) {
//cerr << "skp ngram" << ng << "\n";
continue;
}
if (ng.freq==1) n1++;
else if (ng.freq==2) n2++;
}
//compute statistics of shiftbeta smoothing
if (beta[l]==-1) {
if (n1>0)
beta[l]=(double)n1/(double)(n1 + 2 * n2);
else {
cerr << "no singletons! \n";
beta[l]=1.0;
}
}
cerr << beta[l] << "\n";
}
return 1;
};
