diff options
Diffstat (limited to 'java/src/com/android/inputmethod/latin/UserHistoryForgettingCurveUtils.java')
| -rw-r--r-- | java/src/com/android/inputmethod/latin/UserHistoryForgettingCurveUtils.java | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/java/src/com/android/inputmethod/latin/UserHistoryForgettingCurveUtils.java b/java/src/com/android/inputmethod/latin/UserHistoryForgettingCurveUtils.java new file mode 100644 index 000000000..1de95d7b8 --- /dev/null +++ b/java/src/com/android/inputmethod/latin/UserHistoryForgettingCurveUtils.java @@ -0,0 +1,222 @@ +/* + * Copyright (C) 2012 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. + */ + +package com.android.inputmethod.latin; + +import android.text.format.DateUtils; +import android.util.Log; + +public class UserHistoryForgettingCurveUtils { + private static final String TAG = UserHistoryForgettingCurveUtils.class.getSimpleName(); + private static final boolean DEBUG = false; + private static final int FC_FREQ_MAX = 127; + /* package */ static final int COUNT_MAX = 3; + private static final int FC_LEVEL_MAX = 3; + /* package */ static final int ELAPSED_TIME_MAX = 15; + private static final int ELAPSED_TIME_INTERVAL_HOURS = 6; + private static final long ELAPSED_TIME_INTERVAL_MILLIS = ELAPSED_TIME_INTERVAL_HOURS + * DateUtils.HOUR_IN_MILLIS; + private static final int HALF_LIFE_HOURS = 48; + private static final int MAX_PUSH_ELAPSED = (FC_LEVEL_MAX + 1) * (ELAPSED_TIME_MAX + 1); + + private UserHistoryForgettingCurveUtils() { + // This utility class is not publicly instantiable. + } + + public static class ForgettingCurveParams { + private byte mFc; + long mLastTouchedTime = 0; + private final boolean mIsValid; + + private void updateLastTouchedTime() { + mLastTouchedTime = System.currentTimeMillis(); + } + + public ForgettingCurveParams(boolean isValid) { + this(System.currentTimeMillis(), isValid); + } + + private ForgettingCurveParams(long now, boolean isValid) { + this(pushCount((byte)0, isValid), now, now, isValid); + } + + /** This constructor is called when the user history bigram dictionary is being restored. */ + public ForgettingCurveParams(int fc, long now, long last) { + // All words with level >= 1 had been saved. + // Invalid words with level == 0 had been saved. + // Valid words words with level == 0 had *not* been saved. + this(fc, now, last, fcToLevel((byte)fc) > 0); + } + + private ForgettingCurveParams(int fc, long now, long last, boolean isValid) { + mIsValid = isValid; + mFc = (byte)fc; + mLastTouchedTime = last; + updateElapsedTime(now); + } + + public boolean isValid() { + return mIsValid; + } + + public byte getFc() { + updateElapsedTime(System.currentTimeMillis()); + return mFc; + } + + public int getFrequency() { + updateElapsedTime(System.currentTimeMillis()); + return UserHistoryForgettingCurveUtils.fcToFreq(mFc); + } + + public int notifyTypedAgainAndGetFrequency() { + updateLastTouchedTime(); + // TODO: Check whether this word is valid or not + mFc = pushCount(mFc, false); + return UserHistoryForgettingCurveUtils.fcToFreq(mFc); + } + + private void updateElapsedTime(long now) { + final int elapsedTimeCount = + (int)((now - mLastTouchedTime) / ELAPSED_TIME_INTERVAL_MILLIS); + if (elapsedTimeCount <= 0) { + return; + } + if (elapsedTimeCount >= MAX_PUSH_ELAPSED) { + mLastTouchedTime = now; + mFc = 0; + return; + } + for (int i = 0; i < elapsedTimeCount; ++i) { + mLastTouchedTime += ELAPSED_TIME_INTERVAL_MILLIS; + mFc = pushElapsedTime(mFc); + } + } + } + + /* package */ static int fcToElapsedTime(byte fc) { + return fc & 0x0F; + } + + /* package */ static int fcToCount(byte fc) { + return (fc >> 4) & 0x03; + } + + /* package */ static int fcToLevel(byte fc) { + return (fc >> 6) & 0x03; + } + + private static int calcFreq(int elapsedTime, int count, int level) { + if (level <= 0) { + // Reserved words, just return -1 + return -1; + } + if (count == COUNT_MAX) { + // Temporary promote because it's frequently typed recently + ++level; + } + final int et = Math.min(FC_FREQ_MAX, Math.max(0, elapsedTime)); + final int l = Math.min(FC_LEVEL_MAX, Math.max(0, level)); + return MathUtils.SCORE_TABLE[l - 1][et]; + } + + /* pakcage */ static byte calcFc(int elapsedTime, int count, int level) { + final int et = Math.min(FC_FREQ_MAX, Math.max(0, elapsedTime)); + final int c = Math.min(COUNT_MAX, Math.max(0, count)); + final int l = Math.min(FC_LEVEL_MAX, Math.max(0, level)); + return (byte)(et | (c << 4) | (l << 6)); + } + + public static int fcToFreq(byte fc) { + final int elapsedTime = fcToElapsedTime(fc); + final int count = fcToCount(fc); + final int level = fcToLevel(fc); + return calcFreq(elapsedTime, count, level); + } + + public static byte pushElapsedTime(byte fc) { + int elapsedTime = fcToElapsedTime(fc); + int count = fcToCount(fc); + int level = fcToLevel(fc); + if (elapsedTime >= ELAPSED_TIME_MAX) { + // Downgrade level + elapsedTime = 0; + count = COUNT_MAX; + --level; + } else { + ++elapsedTime; + } + return calcFc(elapsedTime, count, level); + } + + public static byte pushCount(byte fc, boolean isValid) { + final int elapsedTime = fcToElapsedTime(fc); + int count = fcToCount(fc); + int level = fcToLevel(fc); + if ((elapsedTime == 0 && count >= COUNT_MAX) || (isValid && level == 0)) { + // Upgrade level + ++level; + count = 0; + if (DEBUG) { + Log.d(TAG, "Upgrade level."); + } + } else { + ++count; + } + return calcFc(0, count, level); + } + + // TODO: isValid should be false for a word whose frequency is 0, + // or that is not in the dictionary. + /** + * Check wheather we should save the bigram to the SQL DB or not + */ + public static boolean needsToSave(byte fc, boolean isValid, boolean addLevel0Bigram) { + int level = fcToLevel(fc); + if (level == 0) { + if (isValid || !addLevel0Bigram) { + return false; + } + } + final int elapsedTime = fcToElapsedTime(fc); + return (elapsedTime < ELAPSED_TIME_MAX - 1 || level > 0); + } + + private static class MathUtils { + public static final int[][] SCORE_TABLE = new int[FC_LEVEL_MAX][ELAPSED_TIME_MAX + 1]; + static { + for (int i = 0; i < FC_LEVEL_MAX; ++i) { + final float initialFreq; + if (i >= 2) { + initialFreq = FC_FREQ_MAX; + } else if (i == 1) { + initialFreq = FC_FREQ_MAX / 2; + } else if (i == 0) { + initialFreq = FC_FREQ_MAX / 4; + } else { + continue; + } + for (int j = 0; j < ELAPSED_TIME_MAX; ++j) { + final float elapsedHours = j * ELAPSED_TIME_INTERVAL_HOURS; + final float freq = initialFreq + * NativeUtils.powf(initialFreq, elapsedHours / HALF_LIFE_HOURS); + final int intFreq = Math.min(FC_FREQ_MAX, Math.max(0, (int)freq)); + SCORE_TABLE[i][j] = intFreq; + } + } + } + } +} |