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Stochastic decay. 

Bug: 6669677
Change-Id: Ib2d9228b951c77dab7a8675ce9db60677e87e771
main
Keisuke Kuroyanagi 2013-10-02 17:51:12 +09:00
parent 13d5dc914a
commit c76bbceedc
6 changed files with 77 additions and 95 deletions
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12
native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.cpp
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@ -43,7 +43,7 @@ void DynamicBigramListPolicy::getNextBigram(int *const outBigramPos, int *const
}
*outProbability = BigramListReadWriteUtils::getProbabilityFromFlags(bigramFlags);
*outHasNext = BigramListReadWriteUtils::hasNext(bigramFlags);
if (mIsDecayingDict && !ForgettingCurveUtils::isValidBigram(*outProbability)) {
if (mIsDecayingDict && !ForgettingCurveUtils::isValidEncodedProbability(*outProbability)) {
// This bigram is too weak to output.
*outBigramPos = NOT_A_DICT_POS;
} else {
@ -261,8 +261,8 @@ bool DynamicBigramListPolicy::addNewBigramEntryToBigramList(const int bigramTarg
const int originalProbability = BigramListReadWriteUtils::getProbabilityFromFlags(
bigramFlags);
const int probabilityToWrite = mIsDecayingDict ?
ForgettingCurveUtils::getUpdatedBigramProbabilityDelta(
originalProbability, probability) : probability;
ForgettingCurveUtils::getUpdatedEncodedProbability(originalProbability,
probability) : probability;
const BigramListReadWriteUtils::BigramFlags updatedFlags =
BigramListReadWriteUtils::setProbabilityInFlags(bigramFlags,
probabilityToWrite);
@ -294,7 +294,7 @@ bool DynamicBigramListPolicy::writeNewBigramEntry(const int bigramTargetPos, con
int *const writingPos) {
// hasNext is false because we are adding a new bigram entry at the end of the bigram list.
const int probabilityToWrite = mIsDecayingDict ?
ForgettingCurveUtils::getUpdatedBigramProbabilityDelta(NOT_A_PROBABILITY, probability) :
ForgettingCurveUtils::getUpdatedEncodedProbability(NOT_A_PROBABILITY, probability) :
probability;
return BigramListReadWriteUtils::createAndWriteBigramEntry(mBuffer, bigramTargetPos,
probabilityToWrite, false /* hasNext */, writingPos);
@ -365,9 +365,9 @@ bool DynamicBigramListPolicy::updateProbabilityForDecay(
*outRemoved = false;
if (mIsDecayingDict) {
// Update bigram probability for decaying.
const int newProbability = ForgettingCurveUtils::getBigramProbabilityDeltaToSave(
const int newProbability = ForgettingCurveUtils::getEncodedProbabilityToSave(
BigramListReadWriteUtils::getProbabilityFromFlags(bigramFlags));
if (ForgettingCurveUtils::isValidBigram(newProbability)) {
if (ForgettingCurveUtils::isValidEncodedProbability(newProbability)) {
// Write new probability.
const BigramListReadWriteUtils::BigramFlags updatedBigramFlags =
BigramListReadWriteUtils::setProbabilityInFlags(

4
native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
View File

@ -29,14 +29,14 @@ bool DynamicPatriciaTrieGcEventListeners
bool isUselessPtNode = !node->isTerminal();
if (node->isTerminal() && mIsDecayingDict) {
const int newProbability =
ForgettingCurveUtils::getUnigramProbabilityToSave(node->getProbability());
ForgettingCurveUtils::getEncodedProbabilityToSave(node->getProbability());
int writingPos = node->getProbabilityFieldPos();
// Update probability.
if (!DynamicPatriciaTrieWritingUtils::writeProbabilityAndAdvancePosition(
mBuffer, newProbability, &writingPos)) {
return false;
}
if (!ForgettingCurveUtils::isValidUnigram(newProbability)) {
if (!ForgettingCurveUtils::isValidEncodedProbability(newProbability)) {
isUselessPtNode = false;
}
}

2
native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
View File

@ -545,7 +545,7 @@ bool DynamicPatriciaTrieWritingHelper::runGC(const int rootPtNodeArrayPos,
int DynamicPatriciaTrieWritingHelper::getUpdatedProbability(const int originalProbability,
const int newProbability) {
if (mNeedsToDecay) {
return ForgettingCurveUtils::getUpdatedUnigramProbability(originalProbability,
return ForgettingCurveUtils::getUpdatedEncodedProbability(originalProbability,
newProbability);
} else {
return newProbability;

111
native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp
View File

@ -14,6 +14,8 @@
* limitations under the License.
*/
#include <stdlib.h>
#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
#include "suggest/policyimpl/dictionary/utils/probability_utils.h"
@ -26,106 +28,91 @@ const int ForgettingCurveUtils::MAX_BIGRAM_COUNT = 12000;
const int ForgettingCurveUtils::MAX_BIGRAM_COUNT_AFTER_GC = 10000;
const int ForgettingCurveUtils::MAX_COMPUTED_PROBABILITY = 127;
const int ForgettingCurveUtils::MAX_UNIGRAM_PROBABILITY = 120;
const int ForgettingCurveUtils::MIN_VALID_UNIGRAM_PROBABILITY = 24;
const int ForgettingCurveUtils::UNIGRAM_PROBABILITY_STEP = 8;
const int ForgettingCurveUtils::MAX_BIGRAM_PROBABILITY_DELTA = 15;
const int ForgettingCurveUtils::MIN_VALID_BIGRAM_PROBABILITY_DELTA = 3;
const int ForgettingCurveUtils::BIGRAM_PROBABILITY_DELTA_STEP = 1;
const int ForgettingCurveUtils::MAX_ENCODED_PROBABILITY = 15;
const int ForgettingCurveUtils::MIN_VALID_ENCODED_PROBABILITY = 3;
const int ForgettingCurveUtils::ENCODED_PROBABILITY_STEP = 1;
// Currently, we try to decay each uni/bigram once every 2 hours. Accordingly, the expected
// duration of the decay is approximately 66hours.
const float ForgettingCurveUtils::MIN_PROBABILITY_TO_DECAY = 0.03f;
/* static */ int ForgettingCurveUtils::getProbability(const int encodedUnigramProbability,
const int encodedBigramProbabilityDelta) {
const int encodedBigramProbability) {
if (encodedUnigramProbability == NOT_A_PROBABILITY) {
return NOT_A_PROBABILITY;
} else if (encodedBigramProbabilityDelta == NOT_A_PROBABILITY) {
const int rawProbability = ProbabilityUtils::backoff(decodeUnigramProbability(
encodedUnigramProbability));
return min(getDecayedProbability(rawProbability), MAX_COMPUTED_PROBABILITY);
} else if (encodedBigramProbability == NOT_A_PROBABILITY) {
return backoff(decodeUnigramProbability(encodedUnigramProbability));
} else {
const int rawProbability = ProbabilityUtils::computeProbabilityForBigram(
decodeUnigramProbability(encodedUnigramProbability),
decodeBigramProbabilityDelta(encodedBigramProbabilityDelta));
return min(getDecayedProbability(rawProbability), MAX_COMPUTED_PROBABILITY);
const int unigramProbability = decodeUnigramProbability(encodedUnigramProbability);
const int bigramProbability = decodeBigramProbability(encodedBigramProbability);
return min(max(unigramProbability, bigramProbability), MAX_COMPUTED_PROBABILITY);
}
}
/* static */ int ForgettingCurveUtils::getUpdatedUnigramProbability(
// Caveat: Unlike getProbability(), this method doesn't assume special bigram probability encoding
// (i.e. unigram probability + bigram probability delta).
/* static */ int ForgettingCurveUtils::getUpdatedEncodedProbability(
const int originalEncodedProbability, const int newProbability) {
if (originalEncodedProbability == NOT_A_PROBABILITY) {
// The unigram is not in this dictionary.
if (newProbability == NOT_A_PROBABILITY) {
// The unigram is not in other dictionaries.
return 0;
} else {
return MIN_VALID_UNIGRAM_PROBABILITY;
}
} else {
if (newProbability != NOT_A_PROBABILITY
&& originalEncodedProbability < MIN_VALID_UNIGRAM_PROBABILITY) {
return MIN_VALID_UNIGRAM_PROBABILITY;
}
return min(originalEncodedProbability + UNIGRAM_PROBABILITY_STEP, MAX_UNIGRAM_PROBABILITY);
}
}
/* static */ int ForgettingCurveUtils::getUnigramProbabilityToSave(const int encodedProbability) {
return max(encodedProbability - UNIGRAM_PROBABILITY_STEP, 0);
}
/* static */ int ForgettingCurveUtils::getBigramProbabilityDeltaToSave(
const int encodedProbabilityDelta) {
return max(encodedProbabilityDelta - BIGRAM_PROBABILITY_DELTA_STEP, 0);
}
/* static */ int ForgettingCurveUtils::getUpdatedBigramProbabilityDelta(
const int originalEncodedProbabilityDelta, const int newProbability) {
if (originalEncodedProbabilityDelta == NOT_A_PROBABILITY) {
// The bigram relation is not in this dictionary.
if (newProbability == NOT_A_PROBABILITY) {
// The bigram target is not in other dictionaries.
return 0;
} else {
return MIN_VALID_BIGRAM_PROBABILITY_DELTA;
return MIN_VALID_ENCODED_PROBABILITY;
}
} else {
if (newProbability != NOT_A_PROBABILITY
&& originalEncodedProbabilityDelta < MIN_VALID_BIGRAM_PROBABILITY_DELTA) {
return MIN_VALID_BIGRAM_PROBABILITY_DELTA;
&& originalEncodedProbability < MIN_VALID_ENCODED_PROBABILITY) {
return MIN_VALID_ENCODED_PROBABILITY;
}
return min(originalEncodedProbabilityDelta + BIGRAM_PROBABILITY_DELTA_STEP,
MAX_BIGRAM_PROBABILITY_DELTA);
return min(originalEncodedProbability + ENCODED_PROBABILITY_STEP, MAX_ENCODED_PROBABILITY);
}
}
/* static */ int ForgettingCurveUtils::isValidUnigram(const int encodedUnigramProbability) {
return encodedUnigramProbability >= MIN_VALID_UNIGRAM_PROBABILITY;
/* static */ int ForgettingCurveUtils::isValidEncodedProbability(const int encodedProbability) {
return encodedProbability >= MIN_VALID_ENCODED_PROBABILITY;
}
/* static */ int ForgettingCurveUtils::isValidBigram(const int encodedBigramProbabilityDelta) {
return encodedBigramProbabilityDelta >= MIN_VALID_BIGRAM_PROBABILITY_DELTA;
/* static */ int ForgettingCurveUtils::getEncodedProbabilityToSave(const int encodedProbability) {
const int currentEncodedProbability = max(min(encodedProbability, MAX_ENCODED_PROBABILITY), 0);
// TODO: Implement the decay in more proper way.
const float currentRate = static_cast<float>(currentEncodedProbability)
/ static_cast<float>(MAX_ENCODED_PROBABILITY);
const float thresholdToDecay = MIN_PROBABILITY_TO_DECAY
+ (1.0f - MIN_PROBABILITY_TO_DECAY) * (1.0f - currentRate);
const float randValue = static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
if (thresholdToDecay < randValue) {
return max(currentEncodedProbability - ENCODED_PROBABILITY_STEP, 0);
} else {
return currentEncodedProbability;
}
}
/* static */ int ForgettingCurveUtils::decodeUnigramProbability(const int encodedProbability) {
const int probability = encodedProbability - MIN_VALID_UNIGRAM_PROBABILITY;
const int probability = encodedProbability - MIN_VALID_ENCODED_PROBABILITY;
if (probability < 0) {
return NOT_A_PROBABILITY;
} else {
return min(probability, MAX_UNIGRAM_PROBABILITY);
return min(probability, MAX_ENCODED_PROBABILITY) * 8;
}
}
/* static */ int ForgettingCurveUtils::decodeBigramProbabilityDelta(
const int encodedProbabilityDelta) {
const int probabilityDelta = encodedProbabilityDelta - MIN_VALID_BIGRAM_PROBABILITY_DELTA;
if (probabilityDelta < 0) {
/* static */ int ForgettingCurveUtils::decodeBigramProbability(const int encodedProbability) {
const int probability = encodedProbability - MIN_VALID_ENCODED_PROBABILITY;
if (probability < 0) {
return NOT_A_PROBABILITY;
} else {
return min(probabilityDelta, MAX_BIGRAM_PROBABILITY_DELTA);
return min(probability, MAX_ENCODED_PROBABILITY) * 8;
}
}
/* static */ int ForgettingCurveUtils::getDecayedProbability(const int rawProbability) {
return rawProbability;
// See comments in ProbabilityUtils::backoff().
/* static */ int ForgettingCurveUtils::backoff(const int unigramProbability) {
if (unigramProbability == NOT_A_PROBABILITY) {
return NOT_A_PROBABILITY;
} else {
return max(unigramProbability - 8, 0);
}
}
} // namespace latinime

31
native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h
View File

@ -24,7 +24,6 @@ namespace latinime {
// TODO: Check the elapsed time and decrease the probability depending on the time. Time field is
// required to introduced to each terminal PtNode and bigram entry.
// TODO: Quit using bigram probability to indicate the delta.
// TODO: Quit using bigram probability delta.
class ForgettingCurveUtils {
public:
static const int MAX_UNIGRAM_COUNT;
@ -33,38 +32,30 @@ class ForgettingCurveUtils {
static const int MAX_BIGRAM_COUNT_AFTER_GC;
static int getProbability(const int encodedUnigramProbability,
const int encodedBigramProbabilityDelta);
const int encodedBigramProbability);
static int getUpdatedUnigramProbability(const int originalEncodedProbability,
static int getUpdatedEncodedProbability(const int originalEncodedProbability,
const int newProbability);
static int getUpdatedBigramProbabilityDelta(const int originalEncodedProbabilityDelta,
const int newProbability);
static int isValidEncodedProbability(const int encodedProbability);
static int isValidUnigram(const int encodedUnigramProbability);
static int isValidBigram(const int encodedProbabilityDelta);
static int getUnigramProbabilityToSave(const int encodedProbability);
static int getBigramProbabilityDeltaToSave(const int encodedProbabilityDelta);
static int getEncodedProbabilityToSave(const int encodedProbability);
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(ForgettingCurveUtils);
static const int MAX_COMPUTED_PROBABILITY;
static const int MAX_UNIGRAM_PROBABILITY;
static const int MIN_VALID_UNIGRAM_PROBABILITY;
static const int UNIGRAM_PROBABILITY_STEP;
static const int MAX_BIGRAM_PROBABILITY_DELTA;
static const int MIN_VALID_BIGRAM_PROBABILITY_DELTA;
static const int BIGRAM_PROBABILITY_DELTA_STEP;
static const int MAX_ENCODED_PROBABILITY;
static const int MIN_VALID_ENCODED_PROBABILITY;
static const int ENCODED_PROBABILITY_STEP;
static const float MIN_PROBABILITY_TO_DECAY;
static int decodeUnigramProbability(const int encodedProbability);
static int decodeBigramProbabilityDelta(const int encodedProbability);
static int decodeBigramProbability(const int encodedProbability);
static int getDecayedProbability(const int rawProbability);
static int backoff(const int unigramProbability);
};
} // namespace latinime
#endif /* LATINIME_FORGETTING_CURVE_UTILS_H */

12
tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
View File

@ -50,14 +50,18 @@ public class BinaryDictionaryDecayingTests extends AndroidTestCase {
}
private void forcePassingShortTime(final BinaryDictionary binaryDictionary) {
binaryDictionary.getPropertyForTests(SET_NEEDS_TO_DECAY_FOR_TESTING_KEY);
binaryDictionary.flushWithGC();
// Entries having low probability would be suppressed once in 2 GCs.
final int count = 2;
for (int i = 0; i < count; i++) {
binaryDictionary.getPropertyForTests(SET_NEEDS_TO_DECAY_FOR_TESTING_KEY);
binaryDictionary.flushWithGC();
}
}
private void forcePassingLongTime(final BinaryDictionary binaryDictionary) {
// Currently, probabilities are decayed when GC is run. All entries that have never been
// typed in 32 GCs are removed.
final int count = 32;
// typed in 128 GCs would be removed.
final int count = 128;
for (int i = 0; i < count; i++) {
binaryDictionary.getPropertyForTests(SET_NEEDS_TO_DECAY_FOR_TESTING_KEY);
binaryDictionary.flushWithGC();