Add spellcheck and word suggestion to the prediction service

third_party/android_prediction/suggest/policyimpl/utils/edit_distance.h

+/*
+ * 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.
+ */
+
+#ifndef LATINIME_EDIT_DISTANCE_H
+#define LATINIME_EDIT_DISTANCE_H
+
+#include <algorithm>
+
+#include "third_party/android_prediction/defines.h"
+#include "third_party/android_prediction/suggest/policyimpl/utils/edit_distance_policy.h"
+
+namespace latinime {
+
+class EditDistance {
+ public:
+    // CAVEAT: There may be performance penalty if you need the edit distance as an integer value.
+    AK_FORCE_INLINE static float getEditDistance(const EditDistancePolicy *const policy) {
+        const int beforeLength = policy->getString0Length();
+        const int afterLength = policy->getString1Length();
+        float dp[(beforeLength + 1) * (afterLength + 1)];
+        for (int i = 0; i <= beforeLength; ++i) {
+            dp[(afterLength + 1) * i] = i * policy->getInsertionCost(i - 1, -1);
+        }
+        for (int i = 0; i <= afterLength; ++i) {
+            dp[i] = i * policy->getDeletionCost(-1, i - 1);
+        }
+
+        for (int i = 0; i < beforeLength; ++i) {
+            for (int j = 0; j < afterLength; ++j) {
+                dp[(afterLength + 1) * (i + 1) + (j + 1)] = std::min(
+                        dp[(afterLength + 1) * i + (j + 1)] + policy->getInsertionCost(i, j),
+                        std::min(
+                                dp[(afterLength + 1) * (i + 1) + j] + policy->getDeletionCost(i, j),
+                                dp[(afterLength + 1) * i + j] + policy->getSubstitutionCost(i, j)));
+                if (policy->allowTransposition(i, j)) {
+                    dp[(afterLength + 1) * (i + 1) + (j + 1)] = std::min(
+                            dp[(afterLength + 1) * (i + 1) + (j + 1)],
+                            dp[(afterLength + 1) * (i - 1) + (j - 1)]
+                                    + policy->getTranspositionCost(i, j));
+                }
+            }
+        }
+        if (DEBUG_EDIT_DISTANCE) {
+            AKLOGI("IN = %d, OUT = %d", beforeLength, afterLength);
+            for (int i = 0; i < beforeLength + 1; ++i) {
+                for (int j = 0; j < afterLength + 1; ++j) {
+                    AKLOGI("EDIT[%d][%d], %f", i, j, dp[(afterLength + 1) * i + j]);
+                }
+            }
+        }
+        return dp[(beforeLength + 1) * (afterLength + 1) - 1];
+    }
+
+    AK_FORCE_INLINE static void dumpEditDistance10ForDebug(const float *const editDistanceTable,
+            const int editDistanceTableWidth, const int outputLength) {
+        if (DEBUG_DICT) {
+            AKLOGI("EditDistanceTable");
+            for (int i = 0; i <= 10; ++i) {
+                float c[11];
+                for (int j = 0; j <= 10; ++j) {
+                    if (j < editDistanceTableWidth + 1 && i < outputLength + 1) {
+                        c[j] = (editDistanceTable + i * (editDistanceTableWidth + 1))[j];
+                    } else {
+                        c[j] = -1.0f;
+                    }
+                }
+                AKLOGI("[ %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f ]",
+                        c[0], c[1], c[2], c[3], c[4], c[5], c[6], c[7], c[8], c[9], c[10]);
+                (void)c; // To suppress compiler warning
+            }
+        }
+    }
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(EditDistance);
+};
+} // namespace latinime
+
+#endif  // LATINIME_EDIT_DISTANCE_H