1 files changed, 129 insertions, 0 deletions
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/decaying_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/decaying_utils.cpp
new file mode 100644
index 000000000..942a74238
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/decaying_utils.cpp
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2013, 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 "suggest/policyimpl/dictionary/utils/decaying_utils.h"
+
+#include "suggest/policyimpl/dictionary/utils/probability_utils.h"
+
+namespace latinime {
+
+const int DecayingUtils::MAX_UNIGRAM_COUNT = 12000;
+const int DecayingUtils::MAX_UNIGRAM_COUNT_AFTER_GC = 10000;
+const int DecayingUtils::MAX_BIGRAM_COUNT = 12000;
+const int DecayingUtils::MAX_BIGRAM_COUNT_AFTER_GC = 10000;
+
+const int DecayingUtils::MAX_COMPUTED_PROBABILITY = 127;
+const int DecayingUtils::MAX_UNIGRAM_PROBABILITY = 120;
+const int DecayingUtils::MIN_VALID_UNIGRAM_PROBABILITY = 24;
+const int DecayingUtils::UNIGRAM_PROBABILITY_STEP = 8;
+const int DecayingUtils::MAX_BIGRAM_PROBABILITY_DELTA = 15;
+const int DecayingUtils::MIN_VALID_BIGRAM_PROBABILITY_DELTA = 3;
+const int DecayingUtils::BIGRAM_PROBABILITY_DELTA_STEP = 1;
+
+/* static */ int DecayingUtils::getProbability(const int encodedUnigramProbability,
+        const int encodedBigramProbabilityDelta) {
+    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 {
+        const int rawProbability = ProbabilityUtils::computeProbabilityForBigram(
+                decodeUnigramProbability(encodedUnigramProbability),
+                decodeBigramProbabilityDelta(encodedBigramProbabilityDelta));
+        return min(getDecayedProbability(rawProbability), MAX_COMPUTED_PROBABILITY);
+    }
+}
+
+/* static */ int DecayingUtils::getUpdatedUnigramProbability(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 DecayingUtils::getUnigramProbabilityToSave(const int encodedProbability) {
+    return max(encodedProbability - UNIGRAM_PROBABILITY_STEP, 0);
+}
+
+/* static */ int DecayingUtils::getBigramProbabilityDeltaToSave(const int encodedProbabilityDelta) {
+    return max(encodedProbabilityDelta - BIGRAM_PROBABILITY_DELTA_STEP, 0);
+}
+
+/* static */ int DecayingUtils::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;
+        }
+    } else {
+        if (newProbability != NOT_A_PROBABILITY
+                && originalEncodedProbabilityDelta < MIN_VALID_BIGRAM_PROBABILITY_DELTA) {
+            return MIN_VALID_BIGRAM_PROBABILITY_DELTA;
+        }
+        return min(originalEncodedProbabilityDelta + BIGRAM_PROBABILITY_DELTA_STEP,
+                MAX_BIGRAM_PROBABILITY_DELTA);
+    }
+}
+
+/* static */ int DecayingUtils::isValidUnigram(const int encodedUnigramProbability) {
+    return encodedUnigramProbability >= MIN_VALID_UNIGRAM_PROBABILITY;
+}
+
+/* static */ int DecayingUtils::isValidBigram(const int encodedBigramProbabilityDelta) {
+    return encodedBigramProbabilityDelta >= MIN_VALID_BIGRAM_PROBABILITY_DELTA;
+}
+
+/* static */ int DecayingUtils::decodeUnigramProbability(const int encodedProbability) {
+    const int probability = encodedProbability - MIN_VALID_UNIGRAM_PROBABILITY;
+    if (probability < 0) {
+        return NOT_A_PROBABILITY;
+    } else {
+        return min(probability, MAX_UNIGRAM_PROBABILITY);
+    }
+}
+
+/* static */ int DecayingUtils::decodeBigramProbabilityDelta(const int encodedProbabilityDelta) {
+    const int probabilityDelta = encodedProbabilityDelta - MIN_VALID_BIGRAM_PROBABILITY_DELTA;
+    if (probabilityDelta < 0) {
+        return NOT_A_PROBABILITY;
+    } else {
+        return min(probabilityDelta, MAX_BIGRAM_PROBABILITY_DELTA);
+    }
+}
+
+/* static */ int DecayingUtils::getDecayedProbability(const int rawProbability) {
+    return rawProbability;
+}
+
+} // namespace latinime