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Calculate edit distances incrementally.

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Change-Id: I3ee734b9b71351523dc8658cba33d6c8435e348e
This commit is contained in:
Yusuke Nojima 2011-10-13 15:26:45 +09:00
parent 283d35cb6c
commit 04d8737015
2 changed files with 94 additions and 46 deletions
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139
native/src/correction.cpp
View file

@ -27,6 +27,87 @@
namespace latinime {
/////////////////////////////
// edit distance funcitons //
/////////////////////////////
#if 0 /* no longer used */
inline static int editDistance(
int* editDistanceTable, const unsigned short* input,
const int inputLength, const unsigned short* output, const int outputLength) {
// dp[li][lo] dp[a][b] = dp[ a * lo + b]
int* dp = editDistanceTable;
const int li = inputLength + 1;
const int lo = outputLength + 1;
for (int i = 0; i < li; ++i) {
dp[lo * i] = i;
}
for (int i = 0; i < lo; ++i) {
dp[i] = i;
}
for (int i = 0; i < li - 1; ++i) {
for (int j = 0; j < lo - 1; ++j) {
const uint32_t ci = Dictionary::toBaseLowerCase(input[i]);
const uint32_t co = Dictionary::toBaseLowerCase(output[j]);
const uint16_t cost = (ci == co) ? 0 : 1;
dp[(i + 1) * lo + (j + 1)] = min(dp[i * lo + (j + 1)] + 1,
min(dp[(i + 1) * lo + j] + 1, dp[i * lo + j] + cost));
if (i > 0 && j > 0 && ci == Dictionary::toBaseLowerCase(output[j - 1])
&& co == Dictionary::toBaseLowerCase(input[i - 1])) {
dp[(i + 1) * lo + (j + 1)] = min(
dp[(i + 1) * lo + (j + 1)], dp[(i - 1) * lo + (j - 1)] + cost);
}
}
}
if (DEBUG_EDIT_DISTANCE) {
LOGI("IN = %d, OUT = %d", inputLength, outputLength);
for (int i = 0; i < li; ++i) {
for (int j = 0; j < lo; ++j) {
LOGI("EDIT[%d][%d], %d", i, j, dp[i * lo + j]);
}
}
}
return dp[li * lo - 1];
}
#endif
inline static void initEditDistance(int *editDistanceTable) {
for (int i = 0; i <= MAX_WORD_LENGTH_INTERNAL; ++i) {
editDistanceTable[i] = i;
}
}
inline static void calcEditDistanceOneStep(int *editDistanceTable, const unsigned short *input,
const int inputLength, const unsigned short *output, const int outputLength) {
// Let dp[i][j] be editDistanceTable[i * (inputLength + 1) + j].
// Assuming that dp[0][0] ... dp[outputLength - 1][inputLength] are already calculated,
// and calculate dp[ouputLength][0] ... dp[outputLength][inputLength].
int *const current = editDistanceTable + outputLength * (inputLength + 1);
const int *const prev = editDistanceTable + (outputLength - 1) * (inputLength + 1);
const int *const prevprev =
outputLength >= 2 ? editDistanceTable + (outputLength - 2) * (inputLength + 1) : NULL;
current[0] = outputLength;
const uint32_t co = Dictionary::toBaseLowerCase(output[outputLength - 1]);
const uint32_t prevCO =
outputLength >= 2 ? Dictionary::toBaseLowerCase(output[outputLength - 2]) : 0;
for (int i = 1; i <= inputLength; ++i) {
const uint32_t ci = Dictionary::toBaseLowerCase(input[i - 1]);
const uint16_t cost = (ci == co) ? 0 : 1;
current[i] = min(current[i - 1] + 1, min(prev[i] + 1, prev[i - 1] + cost));
if (i >= 2 && prevprev && ci == prevCO
&& co == Dictionary::toBaseLowerCase(input[i - 2])) {
current[i] = min(current[i], prevprev[i - 2] + 1);
}
}
}
inline static int getCurrentEditDistance(
int *editDistanceTable, const int inputLength, const int outputLength) {
return editDistanceTable[(inputLength + 1) * (outputLength + 1) - 1];
}
//////////////////////
// inline functions //
//////////////////////
@ -43,6 +124,7 @@ inline bool Correction::isQuote(const unsigned short c) {
Correction::Correction(const int typedLetterMultiplier, const int fullWordMultiplier)
: TYPED_LETTER_MULTIPLIER(typedLetterMultiplier), FULL_WORD_MULTIPLIER(fullWordMultiplier) {
initEditDistance(mEditDistanceTable);
}
void Correction::initCorrection(const ProximityInfo *pi, const int inputLength,
@ -197,13 +279,21 @@ void Correction::startToTraverseAllNodes() {
}
bool Correction::needsToPrune() const {
// TODO: use edit distance here
return mOutputIndex - 1 >= mMaxDepth || mProximityCount > mMaxEditDistance;
}
void Correction::addCharToCurrentWord(const int32_t c) {
mWord[mOutputIndex] = c;
const unsigned short *primaryInputWord = mProximityInfo->getPrimaryInputWord();
calcEditDistanceOneStep(mEditDistanceTable, primaryInputWord, mInputLength,
mWord, mOutputIndex + 1);
}
// TODO: inline?
Correction::CorrectionType Correction::processSkipChar(
const int32_t c, const bool isTerminal, const bool inputIndexIncremented) {
mWord[mOutputIndex] = c;
addCharToCurrentWord(c);
if (needsToTraverseAllNodes() && isTerminal) {
mTerminalInputIndex = mInputIndex - (inputIndexIncremented ? 1 : 0);
mTerminalOutputIndex = mOutputIndex;
@ -412,7 +502,7 @@ Correction::CorrectionType Correction::processCharAndCalcState(
mProximityInfo->getNormalizedSquaredDistance(mInputIndex, proximityIndex);
}
mWord[mOutputIndex] = c;
addCharToCurrentWord(c);
// 4. Last char excessive correction
mLastCharExceeded = mExcessiveCount == 0 && mSkippedCount == 0 && mTransposedCount == 0
@ -526,47 +616,6 @@ inline static bool isUpperCase(unsigned short c) {
return false;
}
/* static */
inline static int editDistance(
int* editDistanceTable, const unsigned short* input,
const int inputLength, const unsigned short* output, const int outputLength) {
// dp[li][lo] dp[a][b] = dp[ a * lo + b]
int* dp = editDistanceTable;
const int li = inputLength + 1;
const int lo = outputLength + 1;
for (int i = 0; i < li; ++i) {
dp[lo * i] = i;
}
for (int i = 0; i < lo; ++i) {
dp[i] = i;
}
for (int i = 0; i < li - 1; ++i) {
for (int j = 0; j < lo - 1; ++j) {
const uint32_t ci = Dictionary::toBaseLowerCase(input[i]);
const uint32_t co = Dictionary::toBaseLowerCase(output[j]);
const uint16_t cost = (ci == co) ? 0 : 1;
dp[(i + 1) * lo + (j + 1)] = min(dp[i * lo + (j + 1)] + 1,
min(dp[(i + 1) * lo + j] + 1, dp[i * lo + j] + cost));
if (i > 0 && j > 0 && ci == Dictionary::toBaseLowerCase(output[j - 1])
&& co == Dictionary::toBaseLowerCase(input[i - 1])) {
dp[(i + 1) * lo + (j + 1)] = min(
dp[(i + 1) * lo + (j + 1)], dp[(i - 1) * lo + (j - 1)] + cost);
}
}
}
if (DEBUG_EDIT_DISTANCE) {
LOGI("IN = %d, OUT = %d", inputLength, outputLength);
for (int i = 0; i < li; ++i) {
for (int j = 0; j < lo; ++j) {
LOGI("EDIT[%d][%d], %d", i, j, dp[i * lo + j]);
}
}
}
return dp[li * lo - 1];
}
//////////////////////
// RankingAlgorithm //
//////////////////////
@ -612,9 +661,7 @@ int Correction::RankingAlgorithm::calculateFinalFreq(const int inputIndex, const
// TODO: Optimize this.
// TODO: Ignoring edit distance for transposed char, for now
if (transposedCount == 0 && (proximityMatchedCount > 0 || skipped || excessiveCount > 0)) {
const unsigned short* primaryInputWord = proximityInfo->getPrimaryInputWord();
ed = editDistance(editDistanceTable, primaryInputWord,
inputLength, word, outputIndex + 1);
ed = getCurrentEditDistance(editDistanceTable, inputLength, outputIndex + 1);
const int matchWeight = powerIntCapped(typedLetterMultiplier,
max(inputLength, outputIndex + 1) - ed);
multiplyIntCapped(matchWeight, &finalFreq);

1
native/src/correction.h
View file

@ -102,6 +102,7 @@ private:
inline bool isQuote(const unsigned short c);
inline CorrectionType processSkipChar(
const int32_t c, const bool isTerminal, const bool inputIndexIncremented);
inline void addCharToCurrentWord(const int32_t c);
const int TYPED_LETTER_MULTIPLIER;
const int FULL_WORD_MULTIPLIER;