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/*
* libpinyin
* Library to deal with pinyin.
*
* Copyright (C) 2017 Peng Wu <alexepico@gmail.com>
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*/
#ifndef PHONETIC_LOOKUP_HEAP_H
#define PHONETIC_LOOKUP_HEAP_H
template <gint32 nbest>
static inline bool trellis_value_comp(const trellis_value_t &lhs,
const trellis_value_t &rhs) {
/* min heap here */
return trellis_value_less_than<nbest>(&lhs, &rhs);
}
template <gint32 nbest>
struct trellis_node {
private:
gint32 m_nelem;
/* invariant: min heap */
trellis_value_t m_elements[nbest];
public:
trellis_node(){
m_nelem = 0;
/* always assume non-used m_elements contains random data. */
}
public:
gint32 length() { return m_nelem; }
const trellis_value_t * begin() { return m_elements; }
const trellis_value_t * end() { return m_elements + m_nelem; }
bool number() {
for (ssize_t i = 0; i < m_nelem; ++i)
m_elements[i].m_current_index = i;
return true;
}
/* return true if the item is stored into m_elements. */
bool eval_item(const trellis_value_t * item) {
/* min heap here. */
/* still have space */
if (m_nelem < nbest) {
m_elements[m_nelem] = *item;
m_nelem ++;
/* always push heap. */
std_lite::push_heap(m_elements, m_elements + m_nelem, trellis_value_comp<nbest>);
return true;
}
/* find minium item */
trellis_value_t * min = m_elements;
/* compare new item */
if (trellis_value_less_than<nbest>(min, item)) {
std_lite::pop_heap(m_elements, m_elements + m_nelem, trellis_value_comp<nbest>);
m_elements[m_nelem - 1] = *item;
std_lite::push_heap(m_elements, m_elements + m_nelem, trellis_value_comp<nbest>);
return true;
}
return false;
}
};
/* for space usage and performance. */
/* as trellis node only contains one element,
* when the trellis node created, always put one element in it.
* when no trellis node, it represents zero element.
*/
template <>
struct trellis_node <1> {
private:
trellis_value_t m_element;
public:
trellis_node <1> () : m_element(-FLT_MAX) {}
public:
gint32 length() { return 1; }
const trellis_value_t * begin() { return &m_element; }
const trellis_value_t * end() { return &m_element + 1; }
bool number() {
m_element.m_current_index = 0;
return true;
}
/* return true if the item is stored into m_element. */
bool eval_item(const trellis_value_t * item) {
/* no item yet. */
if (0 == m_element.m_sentence_length) {
m_element = *item;
return true;
}
if (trellis_value_less_than<1>(&m_element, item)) {
m_element = *item;
return true;
}
return false;
}
};
#endif
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