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// Copyright (C) 2003--2004 Darren Moore (moore@idiap.ch)
//
// This file is part of Torch 3.1.
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// 3. The name of the author may not be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "Allocator.h"
#include "LMCache.h"
#include "log_add.h"
namespace Torch {
LMCache::LMCache( int max_entries_ , int lm_order , int n_vocab_words )
{
if ( max_entries_ <= 0 )
error("LMCache::LMCache - max_entries_ cannot be <= 0\n") ;
max_entries = max_entries_ ;
entries = (LMCacheEntry **)Allocator::sysAlloc( max_entries * sizeof(LMCacheEntry *) ) ;
for ( int i=0 ; i<max_entries ; i++ )
entries[i] = new LMCacheEntry( lm_order-1 , n_vocab_words ) ;
oldest = -1 ;
n_entries = 0 ;
}
LMCache::~LMCache()
{
if ( entries != NULL )
{
for ( int i=0 ; i<max_entries ; i++ )
delete entries[i] ;
free( entries ) ;
}
}
void LMCache::addEntry( int order , int *words , real prob )
{
// The ordering of the words must be W3 W2 W1 W4 (for a 4-gram LM)
// where W4 is "next" word and remainder are prev words.
int i , j , max_age=0 , n_prev_words=(order-1) ;
// Do we already have an entry for this n-gram ? Just do a linear search.
for ( i=0 ; i<n_entries ; i++ )
{
if ( n_prev_words == entries[i]->n_prev_words )
{
if ( memcmp( words , entries[i]->prev_words , n_prev_words*sizeof(int) ) == 0 )
{
// Yes we do - add the probability to the existing entry
entries[i]->addProb( words[n_prev_words] , prob ) ;
// Increase the age of all cache entries and keep track of the oldest
for ( j=0 ; j<n_entries ; j++ )
{
if ( ++(entries[j]->age) > max_age )
{
max_age = entries[j]->age ;
oldest = j ;
}
}
return ;
}
}
}
// No we don't, we need to add this n-gram to the cache
if ( n_entries < max_entries )
{
// Our cache isn't full - we can simply add the new entry at the end
entries[n_entries]->addNewPrevWords( n_prev_words , words ) ;
entries[n_entries]->addProb( words[n_prev_words] , prob ) ;
n_entries++ ;
}
else
{
// The cache is full - we need to replace the oldest entry with the new one
entries[oldest]->addNewPrevWords( n_prev_words , words ) ;
entries[oldest]->addProb( words[n_prev_words] , prob ) ;
}
// Increase the age of all cache entries and keep track of oldest
for ( i=0 ; i<n_entries ; i++ )
{
if ( ++(entries[i]->age) > max_age )
{
max_age = entries[i]->age ;
oldest = i ;
}
}
}
real LMCache::getProb( int n_words , int *words )
{
// The ordering of the words must be W3 W2 W1 W4 (for a 4-gram LM)
// where W4 is "next" word and remainder are prev words.
int max_age=0 , i , n_prev_words=(n_words-1) ;
real prob = -LOG_ZERO ;
for ( i=0 ; i<n_entries ; i++ )
{
if ( entries[i]->n_prev_words == n_prev_words )
{
if ( memcmp( words , entries[i]->prev_words , n_prev_words*sizeof(int) ) == 0 )
{
prob = entries[i]->getProb( words[n_prev_words] ) ;
break ;
}
}
}
// Increase the age of all cache entries and keep track of oldest
for ( i=0 ; i<n_entries ; i++ )
{
if ( ++(entries[i]->age) > max_age )
{
max_age = entries[i]->age ;
oldest = i ;
}
}
return prob ;
}
}
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