/* probDiff is the new probability which should be added to the prob of
item (which for an initially created item will be zero. If probDiff
plus whatever previously unused prob in item->storeP is over threshold
then recurse */
void
Bchart::
redoP(Item *item, double probDiff)
{
double oldItemP = item->prob();
double itemStoreP = item->storeP() + probDiff;
item->storeP() = itemStoreP;
if ( oldItemP != 0.0 )
if( itemStoreP / oldItemP < storeCutoff )
{
return;
}
item->prob() += itemStoreP;
//cerr << "P( " << *item << " ) goes from " << oldItemP
//<< " -> " << item->prob() << endl;
item->storeP() = 0.0;
if( oldItemP == 0.0 )
{
return;
}
double pRatio = item->prob() / oldItemP;
NeedmeIter nmi(item);
Edge* edge;
while(nmi.next(edge))
{
redoP(edge,pRatio);
}
}
static void
setup_nmi(void)
{
asm("lda #<_nmi");
asm("sta $fffa");
asm("lda #>_nmi");
asm("sta $fffb");
return;
nmi();
}
void
ChartBase::
set_Alphas()
{
Item *snode = get_S();
double tempAlpha[400]; //400 has no particular meaning, just large enough.
if( !snode || snode->prob() == 0.0 )
{
warn( "estimating the counts on a zero-probability sentence" );
return;
}
double sAlpha = 1.0/snode->prob();
snode->poutside() = sAlpha;
/* for each position in the 2D chart, starting at top*/
/* look at every bucket of length j */
for (int j = wrd_count_-1 ; j >= 0 ; j--)
{
for (int i = 0 ; i <= wrd_count_ - j ; i++)
{
Items il = regs[j][i];
list<Item*>::iterator ili = il.begin();
Item* itm;
for(; ili != il.end(); ili++ )
{
itm = *ili;
if(itm != snode) itm->poutside() = 0; //init outside probs to 0;
}
bool valuesChanging = true;
/* do alpha calulcations until values settle down */
ili = il.begin();
while(valuesChanging)
{
valuesChanging = false;
int tempPos = 0; //position in tempAlpha;
ili = il.begin();
for(; ili != il.end(); ili++ )
{
itm = *ili;
if(itm == snode) continue;
double itmalpha = 0;
NeedmeIter nmi(itm);
Edge* e;
while( nmi.next(e) )
{
const Item* lhsItem = e->finishedParent();
if(lhsItem) itmalpha += lhsItem->poutside()
* e->prob();
}
assert(tempPos < 400);
double val = itmalpha/itm->prob();
tempAlpha[tempPos++] = val;
}
/* at this point the new alpha values are stored in tempAlpha */
int temppos = 0;
ili = il.begin();
for(; ili != il.end(); ili++ )
{
itm = *ili;
if(itm == snode) continue;
/* the start symbol for the entire sentence has poutside =1*/
if(i == 0 && j ==wrd_count_-1 &&
itm->term()->name() == "S1")
itm->poutside() = sAlpha;
else
{
double oOutside = itm->poutside();
double nOutside = tempAlpha[temppos];
if(nOutside == 0)
{
if(oOutside != 0) error("Alpha went down");
}
else if(oOutside/nOutside < .95)
{
itm->poutside() = nOutside;
valuesChanging = true;
//cerr << "alpha*beta " << *itm << " = "
//<< (itm->poutside() * itm->prob()) << endl;
}
}
temppos++;
}
if(temppos != tempPos)
{
cerr << "temppos = " << temppos << " and tempPos = "
<< tempPos << " ";
error("Funnly situation in setAlphas");
}
}
}
}
}
