From f0dc0b1b745d78203ca68668a88278a61d0aff04 Mon Sep 17 00:00:00 2001
From: Keisuke Kuroynagi <ksk@google.com>
Date: Fri, 21 Jun 2013 19:11:39 +0900
Subject: [PATCH] Give the best score to the most probable exact match.

Bug: 9490364
Change-Id: If7fe5da190516d4b5f7a41b752ef5960205a5899
---
 native/jni/src/suggest/core/suggest.cpp       | 23 ++++++++++++++++++-
 native/jni/src/suggest/core/suggest.h         |  2 ++
 .../policyimpl/typing/typing_weighting.h      |  3 +++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/native/jni/src/suggest/core/suggest.cpp b/native/jni/src/suggest/core/suggest.cpp
index a8f16c8cb..173a612be 100644
--- a/native/jni/src/suggest/core/suggest.cpp
+++ b/native/jni/src/suggest/core/suggest.cpp
@@ -36,6 +36,7 @@ namespace latinime {
 const int Suggest::MIN_LEN_FOR_MULTI_WORD_AUTOCORRECT = 16;
 const int Suggest::MIN_CONTINUOUS_SUGGESTION_INPUT_SIZE = 2;
 const float Suggest::AUTOCORRECT_CLASSIFICATION_THRESHOLD = 0.33f;
+const int Suggest::FINAL_SCORE_PENALTY_FOR_NOT_BEST_EXACT_MATCHED_WORD = 1;
 
 /**
  * Returns a set of suggestions for the given input touch points. The commitPoint argument indicates
@@ -148,6 +149,8 @@ int Suggest::outputSuggestions(DicTraverseSession *traverseSession, int *frequen
             &doubleLetterTerminalIndex, &doubleLetterLevel);
 
     int maxScore = S_INT_MIN;
+    int bestExactMatchedNodeTerminalIndex = -1;
+    int bestExactMatchedNodeOutputWordIndex = -1;
     // Output suggestion results here
     for (int terminalIndex = 0; terminalIndex < terminalSize && outputWordIndex < MAX_RESULTS;
             ++terminalIndex) {
@@ -186,7 +189,6 @@ int Suggest::outputSuggestions(DicTraverseSession *traverseSession, int *frequen
         const int finalScore = SCORING->calculateFinalScore(
                 compoundDistance, traverseSession->getInputSize(),
                 isForceCommitMultiWords || (isValidWord && SCORING->doesAutoCorrectValidWord()));
-
         maxScore = max(maxScore, finalScore);
 
         if (TRAVERSAL->allowPartialCommit()) {
@@ -200,6 +202,25 @@ int Suggest::outputSuggestions(DicTraverseSession *traverseSession, int *frequen
         if (isValidWord) {
             outputTypes[outputWordIndex] = Dictionary::KIND_CORRECTION | outputTypeFlags;
             frequencies[outputWordIndex] = finalScore;
+            if (isSafeExactMatch) {
+                // Demote exact matches that are not the highest probable node among all exact
+                // matches.
+                const bool isBestTerminal = bestExactMatchedNodeTerminalIndex < 0
+                        || terminals[bestExactMatchedNodeTerminalIndex].getProbability()
+                                < terminalDicNode->getProbability();
+                const int outputWordIndexToBeDemoted = isBestTerminal ?
+                        bestExactMatchedNodeOutputWordIndex : outputWordIndex;
+                if (outputWordIndexToBeDemoted >= 0) {
+                    frequencies[outputWordIndexToBeDemoted] -=
+                            FINAL_SCORE_PENALTY_FOR_NOT_BEST_EXACT_MATCHED_WORD;
+                }
+                if (isBestTerminal) {
+                    // Updates the best exact matched node index.
+                    bestExactMatchedNodeTerminalIndex = terminalIndex;
+                    // Updates the best exact matched output word index.
+                    bestExactMatchedNodeOutputWordIndex = outputWordIndex;
+                }
+            }
             // Populate the outputChars array with the suggested word.
             const int startIndex = outputWordIndex * MAX_WORD_LENGTH;
             terminalDicNode->outputResult(&outputCodePoints[startIndex]);
diff --git a/native/jni/src/suggest/core/suggest.h b/native/jni/src/suggest/core/suggest.h
index 875cbe4e0..752bde9ac 100644
--- a/native/jni/src/suggest/core/suggest.h
+++ b/native/jni/src/suggest/core/suggest.h
@@ -82,6 +82,8 @@ class Suggest : public SuggestInterface {
 
     // Threshold for autocorrection classifier
     static const float AUTOCORRECT_CLASSIFICATION_THRESHOLD;
+    // Final score penalty to exact match words that are not the most probable exact match.
+    static const int FINAL_SCORE_PENALTY_FOR_NOT_BEST_EXACT_MATCHED_WORD;
 
     const Traversal *const TRAVERSAL;
     const Scoring *const SCORING;
diff --git a/native/jni/src/suggest/policyimpl/typing/typing_weighting.h b/native/jni/src/suggest/policyimpl/typing/typing_weighting.h
index a1c99182a..d7656128d 100644
--- a/native/jni/src/suggest/policyimpl/typing/typing_weighting.h
+++ b/native/jni/src/suggest/policyimpl/typing/typing_weighting.h
@@ -163,6 +163,9 @@ class TypingWeighting : public Weighting {
 
     float getTerminalLanguageCost(const DicTraverseSession *const traverseSession,
             const DicNode *const dicNode, const float dicNodeLanguageImprobability) const {
+        // We promote exact matches here to prevent them from being pruned. The final score of
+        // exact match nodes might be demoted later in Suggest::outputSuggestions if there are
+        // multiple exact matches.
         const float languageImprobability = (dicNode->isExactMatch()) ?
                 0.0f : dicNodeLanguageImprobability;
         return languageImprobability * ScoringParams::DISTANCE_WEIGHT_LANGUAGE;