QtInputMethod_GooglePinyin/googlepinyin/ngram.cpp

343 lines
8.7 KiB
C++

/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include "mystdlib.h"
#include "ngram.h"
namespace ime_pinyin {
#define ADD_COUNT 0.3
int comp_double(const void *p1, const void *p2) {
if (*static_cast<const double*>(p1) < *static_cast<const double*>(p2))
return -1;
if (*static_cast<const double*>(p1) > *static_cast<const double*>(p2))
return 1;
return 0;
}
inline double distance(double freq, double code) {
// return fabs(freq - code);
return freq * fabs(log(freq) - log(code));
}
// Find the index of the code value which is nearest to the given freq
int qsearch_nearest(double code_book[], double freq, int start, int end) {
if (start == end)
return start;
if (start + 1 == end) {
if (distance(freq, code_book[end]) > distance(freq, code_book[start]))
return start;
return end;
}
int mid = (start + end) / 2;
if (code_book[mid] > freq)
return qsearch_nearest(code_book, freq, start, mid);
else
return qsearch_nearest(code_book, freq, mid, end);
}
size_t update_code_idx(double freqs[], size_t num, double code_book[],
CODEBOOK_TYPE *code_idx) {
size_t changed = 0;
for (size_t pos = 0; pos < num; pos++) {
CODEBOOK_TYPE idx;
idx = qsearch_nearest(code_book, freqs[pos], 0, kCodeBookSize - 1);
if (idx != code_idx[pos])
changed++;
code_idx[pos] = idx;
}
return changed;
}
double recalculate_kernel(double freqs[], size_t num, double code_book[],
CODEBOOK_TYPE *code_idx) {
double ret = 0;
size_t *item_num = new size_t[kCodeBookSize];
assert(item_num);
memset(item_num, 0, sizeof(size_t) * kCodeBookSize);
double *cb_new = new double[kCodeBookSize];
assert(cb_new);
memset(cb_new, 0, sizeof(double) * kCodeBookSize);
for (size_t pos = 0; pos < num; pos++) {
ret += distance(freqs[pos], code_book[code_idx[pos]]);
cb_new[code_idx[pos]] += freqs[pos];
item_num[code_idx[pos]] += 1;
}
for (size_t code = 0; code < kCodeBookSize; code++) {
assert(item_num[code] > 0);
code_book[code] = cb_new[code] / item_num[code];
}
delete [] item_num;
delete [] cb_new;
return ret;
}
void iterate_codes(double freqs[], size_t num, double code_book[],
CODEBOOK_TYPE *code_idx) {
size_t iter_num = 0;
double delta_last = 0;
do {
size_t changed = update_code_idx(freqs, num, code_book, code_idx);
double delta = recalculate_kernel(freqs, num, code_book, code_idx);
if (kPrintDebug0) {
printf("---Unigram codebook iteration: %d : %d, %.9f\n",
iter_num, changed, delta);
}
iter_num++;
if (iter_num > 1 &&
(delta == 0 || fabs(delta_last - delta)/fabs(delta) < 0.000000001))
break;
delta_last = delta;
} while (true);
}
NGram* NGram::instance_ = NULL;
NGram::NGram() {
initialized_ = false;
idx_num_ = 0;
lma_freq_idx_ = NULL;
sys_score_compensation_ = 0;
#ifdef ___BUILD_MODEL___
freq_codes_df_ = NULL;
#endif
freq_codes_ = NULL;
}
NGram::~NGram() {
if (NULL != lma_freq_idx_)
free(lma_freq_idx_);
#ifdef ___BUILD_MODEL___
if (NULL != freq_codes_df_)
free(freq_codes_df_);
#endif
if (NULL != freq_codes_)
free(freq_codes_);
}
NGram& NGram::get_instance() {
if (NULL == instance_)
instance_ = new NGram();
return *instance_;
}
bool NGram::save_ngram(FILE *fp) {
if (!initialized_ || NULL == fp)
return false;
if (0 == idx_num_ || NULL == freq_codes_ || NULL == lma_freq_idx_)
return false;
if (fwrite(&idx_num_, sizeof(uint32), 1, fp) != 1)
return false;
if (fwrite(freq_codes_, sizeof(LmaScoreType), kCodeBookSize, fp) !=
kCodeBookSize)
return false;
if (fwrite(lma_freq_idx_, sizeof(CODEBOOK_TYPE), idx_num_, fp) != idx_num_)
return false;
return true;
}
bool NGram::load_ngram(FILE *fp) {
if (NULL == fp)
return false;
initialized_ = false;
if (fread(&idx_num_, sizeof(uint32), 1, fp) != 1 )
return false;
if (NULL != lma_freq_idx_)
free(lma_freq_idx_);
if (NULL != freq_codes_)
free(freq_codes_);
lma_freq_idx_ = static_cast<CODEBOOK_TYPE*>
(malloc(idx_num_ * sizeof(CODEBOOK_TYPE)));
freq_codes_ = static_cast<LmaScoreType*>
(malloc(kCodeBookSize * sizeof(LmaScoreType)));
if (NULL == lma_freq_idx_ || NULL == freq_codes_)
return false;
if (fread(freq_codes_, sizeof(LmaScoreType), kCodeBookSize, fp) !=
kCodeBookSize)
return false;
if (fread(lma_freq_idx_, sizeof(CODEBOOK_TYPE), idx_num_, fp) != idx_num_)
return false;
initialized_ = true;
total_freq_none_sys_ = 0;
return true;
}
void NGram::set_total_freq_none_sys(size_t freq_none_sys) {
total_freq_none_sys_ = freq_none_sys;
if (0 == total_freq_none_sys_) {
sys_score_compensation_ = 0;
} else {
double factor = static_cast<double>(kSysDictTotalFreq) / (
kSysDictTotalFreq + total_freq_none_sys_);
sys_score_compensation_ = static_cast<float>(
log(factor) * kLogValueAmplifier);
}
}
// The caller makes sure this oject is initialized.
float NGram::get_uni_psb(LemmaIdType lma_id) {
return static_cast<float>(freq_codes_[lma_freq_idx_[lma_id]]) +
sys_score_compensation_;
}
float NGram::convert_psb_to_score(double psb) {
float score = static_cast<float>(
log(psb) * static_cast<double>(kLogValueAmplifier));
if (score > static_cast<float>(kMaxScore)) {
score = static_cast<float>(kMaxScore);
}
return score;
}
#ifdef ___BUILD_MODEL___
bool NGram::build_unigram(LemmaEntry *lemma_arr, size_t lemma_num,
LemmaIdType next_idx_unused) {
if (NULL == lemma_arr || 0 == lemma_num || next_idx_unused <= 1)
return false;
double total_freq = 0;
double *freqs = new double[next_idx_unused];
if (NULL == freqs)
return false;
freqs[0] = ADD_COUNT;
total_freq += freqs[0];
LemmaIdType idx_now = 0;
for (size_t pos = 0; pos < lemma_num; pos++) {
if (lemma_arr[pos].idx_by_hz == idx_now)
continue;
idx_now++;
assert(lemma_arr[pos].idx_by_hz == idx_now);
freqs[idx_now] = lemma_arr[pos].freq;
if (freqs[idx_now] <= 0)
freqs[idx_now] = 0.3;
total_freq += freqs[idx_now];
}
double max_freq = 0;
idx_num_ = idx_now + 1;
assert(idx_now + 1 == next_idx_unused);
for (size_t pos = 0; pos < idx_num_; pos++) {
freqs[pos] = freqs[pos] / total_freq;
assert(freqs[pos] > 0);
if (freqs[pos] > max_freq)
max_freq = freqs[pos];
}
// calculate the code book
if (NULL == freq_codes_df_)
freq_codes_df_ = new double[kCodeBookSize];
assert(freq_codes_df_);
memset(freq_codes_df_, 0, sizeof(double) * kCodeBookSize);
if (NULL == freq_codes_)
freq_codes_ = new LmaScoreType[kCodeBookSize];
assert(freq_codes_);
memset(freq_codes_, 0, sizeof(LmaScoreType) * kCodeBookSize);
size_t freq_pos = 0;
for (size_t code_pos = 0; code_pos < kCodeBookSize; code_pos++) {
bool found = true;
while (found) {
found = false;
double cand = freqs[freq_pos];
for (size_t i = 0; i < code_pos; i++)
if (freq_codes_df_[i] == cand) {
found = true;
break;
}
if (found)
freq_pos++;
}
freq_codes_df_[code_pos] = freqs[freq_pos];
freq_pos++;
}
myqsort(freq_codes_df_, kCodeBookSize, sizeof(double), comp_double);
if (NULL == lma_freq_idx_)
lma_freq_idx_ = new CODEBOOK_TYPE[idx_num_];
assert(lma_freq_idx_);
iterate_codes(freqs, idx_num_, freq_codes_df_, lma_freq_idx_);
delete [] freqs;
if (kPrintDebug0) {
printf("\n------Language Model Unigram Codebook------\n");
}
for (size_t code_pos = 0; code_pos < kCodeBookSize; code_pos++) {
double log_score = log(freq_codes_df_[code_pos]);
float final_score = convert_psb_to_score(freq_codes_df_[code_pos]);
if (kPrintDebug0) {
printf("code:%d, probability:%.9f, log score:%.3f, final score: %.3f\n",
code_pos, freq_codes_df_[code_pos], log_score, final_score);
}
freq_codes_[code_pos] = static_cast<LmaScoreType>(final_score);
}
initialized_ = true;
return true;
}
#endif
} // namespace ime_pinyin