Add method to encode probability.

Bug: 14425059
Change-Id: I3e5d359ba5fa38f1669f0e98dfae792ff53efbf8

native/jni/NativeFileList.mk

@@ -84,6 +84,7 @@ LATIN_IME_CORE_SRC_FILES := \
         forgetting_curve_utils.cpp \
         format_utils.cpp \
         mmapped_buffer.cpp \
+        probability_utils.cpp \
         sparse_table.cpp \
         trie_map.cpp ) \
     suggest/policyimpl/gesture/gesture_suggest_policy_factory.cpp \
@@ -135,6 +136,7 @@ LATIN_IME_CORE_TEST_FILES := \
     suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer_test.cpp \
     suggest/policyimpl/dictionary/utils/byte_array_utils_test.cpp \
     suggest/policyimpl/dictionary/utils/format_utils_test.cpp \
+    suggest/policyimpl/dictionary/utils/probability_utils_test.cpp \
     suggest/policyimpl/dictionary/utils/sparse_table_test.cpp \
     suggest/policyimpl/dictionary/utils/trie_map_test.cpp \
     suggest/policyimpl/utils/damerau_levenshtein_edit_distance_policy_test.cpp \

native/jni/src/suggest/policyimpl/dictionary/utils/probability_utils.cpp

@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2014, 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/probability_utils.h"
+
+namespace latinime {
+
+const float ProbabilityUtils::PROBABILITY_ENCODING_SCALER = 8.58923700372f;
+
+} // namespace latinime

native/jni/src/suggest/policyimpl/dictionary/utils/probability_utils.h

@@ -17,6 +17,9 @@
 #ifndef LATINIME_PROBABILITY_UTILS_H
 #define LATINIME_PROBABILITY_UTILS_H
 
+#include <algorithm>
+#include <cmath>
+
 #include "defines.h"
 
 namespace latinime {
@@ -47,8 +50,20 @@ class ProbabilityUtils {
                 + static_cast<int>(static_cast<float>(bigramProbability + 1) * stepSize);
     }
 
+    // Encode probability using the same way as we are doing for main dictionaries.
+    static AK_FORCE_INLINE int encodeRawProbability(const float rawProbability) {
+        const float probability = static_cast<float>(MAX_PROBABILITY)
+                + log2f(rawProbability) * PROBABILITY_ENCODING_SCALER;
+        if (probability < 0.0f) {
+            return 0;
+        }
+        return std::min(static_cast<int>(probability + 0.5f), MAX_PROBABILITY);
+    }
+
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(ProbabilityUtils);
+
+    static const float PROBABILITY_ENCODING_SCALER;
 };
 }
 #endif /* LATINIME_PROBABILITY_UTILS_H */

native/jni/tests/suggest/policyimpl/dictionary/utils/probability_utils_test.cpp

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2014 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/probability_utils.h"
+
+#include <gtest/gtest.h>
+
+#include "defines.h"
+
+namespace latinime {
+namespace {
+
+TEST(ProbabilityUtilsTest, TestEncodeRawProbability) {
+    EXPECT_EQ(MAX_PROBABILITY, ProbabilityUtils::encodeRawProbability(1.0f));
+    EXPECT_EQ(MAX_PROBABILITY - 9, ProbabilityUtils::encodeRawProbability(0.5f));
+    EXPECT_EQ(0, ProbabilityUtils::encodeRawProbability(0.0f));
+}
+
+}  // namespace
+}  // namespace latinime