LatinIME/native/jni/src/proximity_info_state_utils.cpp

/*
 * 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 <cmath>
#include <cstring> // for memset()
#include <sstream> // for debug prints
#include <vector>

#include "defines.h"
#include "geometry_utils.h"
#include "proximity_info.h"
#include "proximity_info_params.h"
#include "proximity_info_state_utils.h"

namespace latinime {

/* static */ int ProximityInfoStateUtils::trimLastTwoTouchPoints(std::vector<int> *sampledInputXs,
        std::vector<int> *sampledInputYs, std::vector<int> *sampledInputTimes,
        std::vector<int> *sampledLengthCache, std::vector<int> *sampledInputIndice) {
    const int nextStartIndex = (*sampledInputIndice)[sampledInputIndice->size() - 2];
    popInputData(sampledInputXs, sampledInputYs, sampledInputTimes, sampledLengthCache,
            sampledInputIndice);
    popInputData(sampledInputXs, sampledInputYs, sampledInputTimes, sampledLengthCache,
            sampledInputIndice);
    return nextStartIndex;
}

/* static */ int ProximityInfoStateUtils::updateTouchPoints(const int mostCommonKeyWidth,
        const ProximityInfo *const proximityInfo, const int maxPointToKeyLength,
        const int *const inputProximities, const int *const inputXCoordinates,
        const int *const inputYCoordinates, const int *const times, const int *const pointerIds,
        const int inputSize, const bool isGeometric, const int pointerId,
        const int pushTouchPointStartIndex, std::vector<int> *sampledInputXs,
        std::vector<int> *sampledInputYs, std::vector<int> *sampledInputTimes,
        std::vector<int> *sampledLengthCache, std::vector<int> *sampledInputIndice) {
    if (DEBUG_SAMPLING_POINTS) {
        if (times) {
            for (int i = 0; i < inputSize; ++i) {
                AKLOGI("(%d) x %d, y %d, time %d",
                        i, inputXCoordinates[i], inputYCoordinates[i], times[i]);
            }
        }
    }
#ifdef DO_ASSERT_TEST
    if (times) {
        for (int i = 0; i < inputSize; ++i) {
            if (i > 0) {
                if (times[i] < times[i - 1]) {
                    AKLOGI("Invalid time sequence. %d, %d", times[i - 1], times[i]);
                    ASSERT(false);
                }
            }
        }
    }
#endif
    const bool proximityOnly = !isGeometric
            && (inputXCoordinates[0] < 0 || inputYCoordinates[0] < 0);
    int lastInputIndex = pushTouchPointStartIndex;
    for (int i = lastInputIndex; i < inputSize; ++i) {
        const int pid = pointerIds ? pointerIds[i] : 0;
        if (pointerId == pid) {
            lastInputIndex = i;
        }
    }
    if (DEBUG_GEO_FULL) {
        AKLOGI("Init ProximityInfoState: last input index = %d", lastInputIndex);
    }
    // Working space to save near keys distances for current, prev and prevprev input point.
    NearKeysDistanceMap nearKeysDistances[3];
    // These pointers are swapped for each inputs points.
    NearKeysDistanceMap *currentNearKeysDistances = &nearKeysDistances[0];
    NearKeysDistanceMap *prevNearKeysDistances = &nearKeysDistances[1];
    NearKeysDistanceMap *prevPrevNearKeysDistances = &nearKeysDistances[2];
    // "sumAngle" is accumulated by each angle of input points. And when "sumAngle" exceeds
    // the threshold we save that point, reset sumAngle. This aims to keep the figure of
    // the curve.
    float sumAngle = 0.0f;

    for (int i = pushTouchPointStartIndex; i <= lastInputIndex; ++i) {
        // Assuming pointerId == 0 if pointerIds is null.
        const int pid = pointerIds ? pointerIds[i] : 0;
        if (DEBUG_GEO_FULL) {
            AKLOGI("Init ProximityInfoState: (%d)PID = %d", i, pid);
        }
        if (pointerId == pid) {
            const int c = isGeometric ?
                    NOT_A_COORDINATE : getPrimaryCodePointAt(inputProximities, i);
            const int x = proximityOnly ? NOT_A_COORDINATE : inputXCoordinates[i];
            const int y = proximityOnly ? NOT_A_COORDINATE : inputYCoordinates[i];
            const int time = times ? times[i] : -1;

            if (i > 1) {
                const float prevAngle = getAngle(
                        inputXCoordinates[i - 2], inputYCoordinates[i - 2],
                        inputXCoordinates[i - 1], inputYCoordinates[i - 1]);
                const float currentAngle =
                        getAngle(inputXCoordinates[i - 1], inputYCoordinates[i - 1], x, y);
                sumAngle += getAngleDiff(prevAngle, currentAngle);
            }

            if (pushTouchPoint(mostCommonKeyWidth, proximityInfo, maxPointToKeyLength,
                    i, c, x, y, time, isGeometric /* doSampling */,
                    i == lastInputIndex, sumAngle, currentNearKeysDistances,
                    prevNearKeysDistances, prevPrevNearKeysDistances,
                    sampledInputXs, sampledInputYs, sampledInputTimes, sampledLengthCache,
                    sampledInputIndice)) {
                // Previous point information was popped.
                NearKeysDistanceMap *tmp = prevNearKeysDistances;
                prevNearKeysDistances = currentNearKeysDistances;
                currentNearKeysDistances = tmp;
            } else {
                NearKeysDistanceMap *tmp = prevPrevNearKeysDistances;
                prevPrevNearKeysDistances = prevNearKeysDistances;
                prevNearKeysDistances = currentNearKeysDistances;
                currentNearKeysDistances = tmp;
                sumAngle = 0.0f;
            }
        }
    }
    return sampledInputXs->size();
}

/* static */ const int *ProximityInfoStateUtils::getProximityCodePointsAt(
        const int *const inputProximities, const int index) {
    return inputProximities + (index * MAX_PROXIMITY_CHARS_SIZE);
}

/* static */ int ProximityInfoStateUtils::getPrimaryCodePointAt(
        const int *const inputProximities, const int index) {
    return getProximityCodePointsAt(inputProximities, index)[0];
}

/* static */ void ProximityInfoStateUtils::initPrimaryInputWord(
        const int inputSize, const int *const inputProximities, int *primaryInputWord) {
    memset(primaryInputWord, 0, sizeof(primaryInputWord[0]) * MAX_WORD_LENGTH);
    for (int i = 0; i < inputSize; ++i) {
        primaryInputWord[i] = getPrimaryCodePointAt(inputProximities, i);
    }
}

/* static */ float ProximityInfoStateUtils::calculateSquaredDistanceFromSweetSpotCenter(
        const ProximityInfo *const proximityInfo, const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs, const int keyIndex,
        const int inputIndex) {
    const float sweetSpotCenterX = proximityInfo->getSweetSpotCenterXAt(keyIndex);
    const float sweetSpotCenterY = proximityInfo->getSweetSpotCenterYAt(keyIndex);
    const float inputX = static_cast<float>((*sampledInputXs)[inputIndex]);
    const float inputY = static_cast<float>((*sampledInputYs)[inputIndex]);
    return SQUARE_FLOAT(inputX - sweetSpotCenterX) + SQUARE_FLOAT(inputY - sweetSpotCenterY);
}

/* static */ float ProximityInfoStateUtils::calculateNormalizedSquaredDistance(
        const ProximityInfo *const proximityInfo, const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        const int keyIndex, const int inputIndex) {
    if (keyIndex == NOT_AN_INDEX) {
        return ProximityInfoParams::NOT_A_DISTANCE_FLOAT;
    }
    if (!proximityInfo->hasSweetSpotData(keyIndex)) {
        return ProximityInfoParams::NOT_A_DISTANCE_FLOAT;
    }
    if (NOT_A_COORDINATE == (*sampledInputXs)[inputIndex]) {
        return ProximityInfoParams::NOT_A_DISTANCE_FLOAT;
    }
    const float squaredDistance = calculateSquaredDistanceFromSweetSpotCenter(proximityInfo,
            sampledInputXs, sampledInputYs, keyIndex, inputIndex);
    const float squaredRadius = SQUARE_FLOAT(proximityInfo->getSweetSpotRadiiAt(keyIndex));
    return squaredDistance / squaredRadius;
}

/* static */ void ProximityInfoStateUtils::initNormalizedSquaredDistances(
        const ProximityInfo *const proximityInfo, const int inputSize,
        const int *inputXCoordinates, const int *inputYCoordinates,
        const int *const inputProximities,
        const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        int *normalizedSquaredDistances) {
    memset(normalizedSquaredDistances, NOT_A_DISTANCE,
            sizeof(normalizedSquaredDistances[0]) * MAX_PROXIMITY_CHARS_SIZE * MAX_WORD_LENGTH);
    const bool hasInputCoordinates = sampledInputXs->size() > 0 && sampledInputYs->size() > 0;
    for (int i = 0; i < inputSize; ++i) {
        const int *proximityCodePoints = getProximityCodePointsAt(inputProximities, i);
        const int primaryKey = proximityCodePoints[0];
        const int x = inputXCoordinates[i];
        const int y = inputYCoordinates[i];
        if (DEBUG_PROXIMITY_CHARS) {
            int a = x + y + primaryKey;
            a += 0;
            AKLOGI("--- Primary = %c, x = %d, y = %d", primaryKey, x, y);
        }
        for (int j = 0; j < MAX_PROXIMITY_CHARS_SIZE && proximityCodePoints[j] > 0;
                ++j) {
            const int currentCodePoint = proximityCodePoints[j];
            const float squaredDistance =
                    hasInputCoordinates ? calculateNormalizedSquaredDistance(
                            proximityInfo, sampledInputXs, sampledInputYs,
                            proximityInfo->getKeyIndexOf(currentCodePoint), i) :
                            ProximityInfoParams::NOT_A_DISTANCE_FLOAT;
            if (squaredDistance >= 0.0f) {
                normalizedSquaredDistances[i * MAX_PROXIMITY_CHARS_SIZE + j] =
                        (int) (squaredDistance
                                * ProximityInfoParams::NORMALIZED_SQUARED_DISTANCE_SCALING_FACTOR);
            } else {
                normalizedSquaredDistances[i * MAX_PROXIMITY_CHARS_SIZE + j] =
                        (j == 0) ? EQUIVALENT_CHAR_WITHOUT_DISTANCE_INFO :
                                PROXIMITY_CHAR_WITHOUT_DISTANCE_INFO;
            }
            if (DEBUG_PROXIMITY_CHARS) {
                AKLOGI("--- Proximity (%d) = %c", j, currentCodePoint);
            }
        }
    }

}

/* static */ void ProximityInfoStateUtils::initGeometricDistanceInfos(
        const ProximityInfo *const proximityInfo, const int keyCount,
        const int sampledInputSize, const int lastSavedInputSize,
        const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        std::vector<NearKeycodesSet> *SampledNearKeysVector,
        std::vector<float> *SampledDistanceCache_G) {
    SampledNearKeysVector->resize(sampledInputSize);
    SampledDistanceCache_G->resize(sampledInputSize * keyCount);
    for (int i = lastSavedInputSize; i < sampledInputSize; ++i) {
        (*SampledNearKeysVector)[i].reset();
        static const float NEAR_KEY_NORMALIZED_SQUARED_THRESHOLD = 4.0f;
        for (int k = 0; k < keyCount; ++k) {
            const int index = i * keyCount + k;
            const int x = (*sampledInputXs)[i];
            const int y = (*sampledInputYs)[i];
            const float normalizedSquaredDistance =
                    proximityInfo->getNormalizedSquaredDistanceFromCenterFloatG(k, x, y);
            (*SampledDistanceCache_G)[index] = normalizedSquaredDistance;
            if (normalizedSquaredDistance < NEAR_KEY_NORMALIZED_SQUARED_THRESHOLD) {
                (*SampledNearKeysVector)[i][k] = true;
            }
        }
    }
}

/* static */ void ProximityInfoStateUtils::popInputData(std::vector<int> *sampledInputXs,
        std::vector<int> *sampledInputYs, std::vector<int> *sampledInputTimes,
        std::vector<int> *sampledLengthCache, std::vector<int> *sampledInputIndice) {
    sampledInputXs->pop_back();
    sampledInputYs->pop_back();
    sampledInputTimes->pop_back();
    sampledLengthCache->pop_back();
    sampledInputIndice->pop_back();
}

/* static */ float ProximityInfoStateUtils::refreshSpeedRates(const int inputSize,
        const int *const xCoordinates, const int *const yCoordinates, const int *const times,
        const int lastSavedInputSize, const int sampledInputSize,
        const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        const std::vector<int> *const sampledInputTimes,
        const std::vector<int> *const sampledLengthCache,
        const std::vector<int> *const sampledInputIndice, std::vector<float> *sampledSpeedRates,
        std::vector<float> *sampledDirections) {
    // Relative speed calculation.
    const int sumDuration = sampledInputTimes->back() - sampledInputTimes->front();
    const int sumLength = sampledLengthCache->back() - sampledLengthCache->front();
    const float averageSpeed = static_cast<float>(sumLength) / static_cast<float>(sumDuration);
    sampledSpeedRates->resize(sampledInputSize);
    for (int i = lastSavedInputSize; i < sampledInputSize; ++i) {
        const int index = (*sampledInputIndice)[i];
        int length = 0;
        int duration = 0;

        // Calculate velocity by using distances and durations of
        // NUM_POINTS_FOR_SPEED_CALCULATION points for both forward and backward.
        static const int NUM_POINTS_FOR_SPEED_CALCULATION = 2;
        for (int j = index; j < min(inputSize - 1, index + NUM_POINTS_FOR_SPEED_CALCULATION);
                ++j) {
            if (i < sampledInputSize - 1 && j >= (*sampledInputIndice)[i + 1]) {
                break;
            }
            length += getDistanceInt(xCoordinates[j], yCoordinates[j],
                    xCoordinates[j + 1], yCoordinates[j + 1]);
            duration += times[j + 1] - times[j];
        }
        for (int j = index - 1; j >= max(0, index - NUM_POINTS_FOR_SPEED_CALCULATION); --j) {
            if (i > 0 && j < (*sampledInputIndice)[i - 1]) {
                break;
            }
            // TODO: use mSampledLengthCache instead?
            length += getDistanceInt(xCoordinates[j], yCoordinates[j],
                    xCoordinates[j + 1], yCoordinates[j + 1]);
            duration += times[j + 1] - times[j];
        }
        if (duration == 0 || sumDuration == 0) {
            // Cannot calculate speed; thus, it gives an average value (1.0);
            (*sampledSpeedRates)[i] = 1.0f;
        } else {
            const float speed = static_cast<float>(length) / static_cast<float>(duration);
            (*sampledSpeedRates)[i] = speed / averageSpeed;
        }
    }

    // Direction calculation.
    sampledDirections->resize(sampledInputSize - 1);
    for (int i = max(0, lastSavedInputSize - 1); i < sampledInputSize - 1; ++i) {
        (*sampledDirections)[i] = getDirection(sampledInputXs, sampledInputYs, i, i + 1);
    }
    return averageSpeed;
}

/* static */ void ProximityInfoStateUtils::refreshBeelineSpeedRates(const int mostCommonKeyWidth,
        const float averageSpeed, const int inputSize, const int *const xCoordinates,
        const int *const yCoordinates, const int *times, const int sampledInputSize,
        const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs, const std::vector<int> *const inputIndice,
        std::vector<int> *beelineSpeedPercentiles) {
    if (DEBUG_SAMPLING_POINTS) {
        AKLOGI("--- refresh beeline speed rates");
    }
    beelineSpeedPercentiles->resize(sampledInputSize);
    for (int i = 0; i < sampledInputSize; ++i) {
        (*beelineSpeedPercentiles)[i] = static_cast<int>(calculateBeelineSpeedRate(
                mostCommonKeyWidth, averageSpeed, i, inputSize, xCoordinates, yCoordinates, times,
                sampledInputSize, sampledInputXs, sampledInputYs, inputIndice) * MAX_PERCENTILE);
    }
}

/* static */float ProximityInfoStateUtils::getDirection(
        const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs, const int index0, const int index1) {
    ASSERT(sampledInputXs && sampledInputYs);
    const int sampledInputSize =sampledInputXs->size();
    if (index0 < 0 || index0 > sampledInputSize - 1) {
        return 0.0f;
    }
    if (index1 < 0 || index1 > sampledInputSize - 1) {
        return 0.0f;
    }
    const int x1 = (*sampledInputXs)[index0];
    const int y1 = (*sampledInputYs)[index0];
    const int x2 = (*sampledInputXs)[index1];
    const int y2 = (*sampledInputYs)[index1];
    return getAngle(x1, y1, x2, y2);
}

// Calculating point to key distance for all near keys and returning the distance between
// the given point and the nearest key position.
/* static */ float ProximityInfoStateUtils::updateNearKeysDistances(
        const ProximityInfo *const proximityInfo, const float maxPointToKeyLength, const int x,
        const int y, NearKeysDistanceMap *const currentNearKeysDistances) {
    static const float NEAR_KEY_THRESHOLD = 2.0f;

    currentNearKeysDistances->clear();
    const int keyCount = proximityInfo->getKeyCount();
    float nearestKeyDistance = maxPointToKeyLength;
    for (int k = 0; k < keyCount; ++k) {
        const float dist = proximityInfo->getNormalizedSquaredDistanceFromCenterFloatG(k, x, y);
        if (dist < NEAR_KEY_THRESHOLD) {
            currentNearKeysDistances->insert(std::pair<int, float>(k, dist));
        }
        if (nearestKeyDistance > dist) {
            nearestKeyDistance = dist;
        }
    }
    return nearestKeyDistance;
}

// Check if previous point is at local minimum position to near keys.
/* static */ bool ProximityInfoStateUtils::isPrevLocalMin(
        const NearKeysDistanceMap *const currentNearKeysDistances,
        const NearKeysDistanceMap *const prevNearKeysDistances,
        const NearKeysDistanceMap *const prevPrevNearKeysDistances) {
    static const float MARGIN = 0.01f;

    for (NearKeysDistanceMap::const_iterator it = prevNearKeysDistances->begin();
            it != prevNearKeysDistances->end(); ++it) {
        NearKeysDistanceMap::const_iterator itPP = prevPrevNearKeysDistances->find(it->first);
        NearKeysDistanceMap::const_iterator itC = currentNearKeysDistances->find(it->first);
        if ((itPP == prevPrevNearKeysDistances->end() || itPP->second > it->second + MARGIN)
                && (itC == currentNearKeysDistances->end() || itC->second > it->second + MARGIN)) {
            return true;
        }
    }
    return false;
}

// Calculating a point score that indicates usefulness of the point.
/* static */ float ProximityInfoStateUtils::getPointScore(const int mostCommonKeyWidth,
        const int x, const int y, const int time, const bool lastPoint, const float nearest,
        const float sumAngle, const NearKeysDistanceMap *const currentNearKeysDistances,
        const NearKeysDistanceMap *const prevNearKeysDistances,
        const NearKeysDistanceMap *const prevPrevNearKeysDistances,
        std::vector<int> *sampledInputXs, std::vector<int> *sampledInputYs) {
    static const int DISTANCE_BASE_SCALE = 100;
    static const float NEAR_KEY_THRESHOLD = 0.6f;
    static const int CORNER_CHECK_DISTANCE_THRESHOLD_SCALE = 25;
    static const float NOT_LOCALMIN_DISTANCE_SCORE = -1.0f;
    static const float LOCALMIN_DISTANCE_AND_NEAR_TO_KEY_SCORE = 1.0f;
    static const float CORNER_ANGLE_THRESHOLD = M_PI_F * 2.0f / 3.0f;
    static const float CORNER_SUM_ANGLE_THRESHOLD = M_PI_F / 4.0f;
    static const float CORNER_SCORE = 1.0f;

    const size_t size = sampledInputXs->size();
    // If there is only one point, add this point. Besides, if the previous point's distance map
    // is empty, we re-compute nearby keys distances from the current point.
    // Note that the current point is the first point in the incremental input that needs to
    // be re-computed.
    if (size <= 1 || prevNearKeysDistances->empty()) {
        return 0.0f;
    }

    const int baseSampleRate = mostCommonKeyWidth;
    const int distPrev = getDistanceInt(sampledInputXs->back(), sampledInputYs->back(),
            (*sampledInputXs)[size - 2], (*sampledInputYs)[size - 2]) * DISTANCE_BASE_SCALE;
    float score = 0.0f;

    // Location
    if (!isPrevLocalMin(currentNearKeysDistances, prevNearKeysDistances,
        prevPrevNearKeysDistances)) {
        score += NOT_LOCALMIN_DISTANCE_SCORE;
    } else if (nearest < NEAR_KEY_THRESHOLD) {
        // Promote points nearby keys
        score += LOCALMIN_DISTANCE_AND_NEAR_TO_KEY_SCORE;
    }
    // Angle
    const float angle1 = getAngle(x, y, sampledInputXs->back(), sampledInputYs->back());
    const float angle2 = getAngle(sampledInputXs->back(), sampledInputYs->back(),
            (*sampledInputXs)[size - 2], (*sampledInputYs)[size - 2]);
    const float angleDiff = getAngleDiff(angle1, angle2);

    // Save corner
    if (distPrev > baseSampleRate * CORNER_CHECK_DISTANCE_THRESHOLD_SCALE
            && (sumAngle > CORNER_SUM_ANGLE_THRESHOLD || angleDiff > CORNER_ANGLE_THRESHOLD)) {
        score += CORNER_SCORE;
    }
    return score;
}

// Sampling touch point and pushing information to vectors.
// Returning if previous point is popped or not.
/* static */ bool ProximityInfoStateUtils::pushTouchPoint(const int mostCommonKeyWidth,
        const ProximityInfo *const proximityInfo, const int maxPointToKeyLength,
        const int inputIndex, const int nodeCodePoint, int x, int y,
        const int time, const bool doSampling, const bool isLastPoint, const float sumAngle,
        NearKeysDistanceMap *const currentNearKeysDistances,
        const NearKeysDistanceMap *const prevNearKeysDistances,
        const NearKeysDistanceMap *const prevPrevNearKeysDistances,
        std::vector<int> *sampledInputXs, std::vector<int> *sampledInputYs,
        std::vector<int> *sampledInputTimes, std::vector<int> *sampledLengthCache,
        std::vector<int> *sampledInputIndice) {
    static const int LAST_POINT_SKIP_DISTANCE_SCALE = 4;

    size_t size = sampledInputXs->size();
    bool popped = false;
    if (nodeCodePoint < 0 && doSampling) {
        const float nearest = updateNearKeysDistances(
                proximityInfo, maxPointToKeyLength, x, y, currentNearKeysDistances);
        const float score = getPointScore(mostCommonKeyWidth, x, y, time, isLastPoint, nearest,
                sumAngle, currentNearKeysDistances, prevNearKeysDistances,
                prevPrevNearKeysDistances, sampledInputXs, sampledInputYs);
        if (score < 0) {
            // Pop previous point because it would be useless.
            popInputData(sampledInputXs, sampledInputYs, sampledInputTimes, sampledLengthCache,
                    sampledInputIndice);
            size = sampledInputXs->size();
            popped = true;
        } else {
            popped = false;
        }
        // Check if the last point should be skipped.
        if (isLastPoint && size > 0) {
            if (getDistanceInt(x, y, sampledInputXs->back(),
                    sampledInputYs->back()) * LAST_POINT_SKIP_DISTANCE_SCALE
                            < mostCommonKeyWidth) {
                // This point is not used because it's too close to the previous point.
                if (DEBUG_GEO_FULL) {
                    AKLOGI("p0: size = %zd, x = %d, y = %d, lx = %d, ly = %d, dist = %d, "
                           "width = %d", size, x, y, sampledInputXs->back(),
                           sampledInputYs->back(), getDistanceInt(
                                   x, y, sampledInputXs->back(), sampledInputYs->back()),
                           mostCommonKeyWidth / LAST_POINT_SKIP_DISTANCE_SCALE);
                }
                return popped;
            }
        }
    }

    if (nodeCodePoint >= 0 && (x < 0 || y < 0)) {
        const int keyId = proximityInfo->getKeyIndexOf(nodeCodePoint);
        if (keyId >= 0) {
            x = proximityInfo->getKeyCenterXOfKeyIdG(keyId);
            y = proximityInfo->getKeyCenterYOfKeyIdG(keyId);
        }
    }

    // Pushing point information.
    if (size > 0) {
        sampledLengthCache->push_back(
                sampledLengthCache->back() + getDistanceInt(
                        x, y, sampledInputXs->back(), sampledInputYs->back()));
    } else {
        sampledLengthCache->push_back(0);
    }
    sampledInputXs->push_back(x);
    sampledInputYs->push_back(y);
    sampledInputTimes->push_back(time);
    sampledInputIndice->push_back(inputIndex);
    if (DEBUG_GEO_FULL) {
        AKLOGI("pushTouchPoint: x = %03d, y = %03d, time = %d, index = %d, popped ? %01d",
                x, y, time, inputIndex, popped);
    }
    return popped;
}

/* static */ float ProximityInfoStateUtils::calculateBeelineSpeedRate(const int mostCommonKeyWidth,
        const float averageSpeed, const int id, const int inputSize, const int *const xCoordinates,
        const int *const yCoordinates, const int *times, const int sampledInputSize,
        const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        const std::vector<int> *const sampledInputIndices) {
    if (sampledInputSize <= 0 || averageSpeed < 0.001f) {
        if (DEBUG_SAMPLING_POINTS) {
            AKLOGI("--- invalid state: cancel. size = %d, ave = %f",
                    sampledInputSize, averageSpeed);
        }
        return 1.0f;
    }
    const int lookupRadius = mostCommonKeyWidth
            * ProximityInfoParams::LOOKUP_RADIUS_PERCENTILE / MAX_PERCENTILE;
    const int x0 = (*sampledInputXs)[id];
    const int y0 = (*sampledInputYs)[id];
    const int actualInputIndex = (*sampledInputIndices)[id];
    int tempTime = 0;
    int tempBeelineDistance = 0;
    int start = actualInputIndex;
    // lookup forward
    while (start > 0 && tempBeelineDistance < lookupRadius) {
        tempTime += times[start] - times[start - 1];
        --start;
        tempBeelineDistance = getDistanceInt(x0, y0, xCoordinates[start], yCoordinates[start]);
    }
    // Exclusive unless this is an edge point
    if (start > 0 && start < actualInputIndex) {
        ++start;
    }
    tempTime= 0;
    tempBeelineDistance = 0;
    int end = actualInputIndex;
    // lookup backward
    while (end < (inputSize - 1) && tempBeelineDistance < lookupRadius) {
        tempTime += times[end + 1] - times[end];
        ++end;
        tempBeelineDistance = getDistanceInt(x0, y0, xCoordinates[end], yCoordinates[end]);
    }
    // Exclusive unless this is an edge point
    if (end > actualInputIndex && end < (inputSize - 1)) {
        --end;
    }

    if (start >= end) {
        if (DEBUG_DOUBLE_LETTER) {
            AKLOGI("--- double letter: start == end %d", start);
        }
        return 1.0f;
    }

    const int x2 = xCoordinates[start];
    const int y2 = yCoordinates[start];
    const int x3 = xCoordinates[end];
    const int y3 = yCoordinates[end];
    const int beelineDistance = getDistanceInt(x2, y2, x3, y3);
    int adjustedStartTime = times[start];
    if (start == 0 && actualInputIndex == 0 && inputSize > 1) {
        adjustedStartTime += ProximityInfoParams::FIRST_POINT_TIME_OFFSET_MILLIS;
    }
    int adjustedEndTime = times[end];
    if (end == (inputSize - 1) && inputSize > 1) {
        adjustedEndTime -= ProximityInfoParams::FIRST_POINT_TIME_OFFSET_MILLIS;
    }
    const int time = adjustedEndTime - adjustedStartTime;
    if (time <= 0) {
        return 1.0f;
    }

    if (time >= ProximityInfoParams::STRONG_DOUBLE_LETTER_TIME_MILLIS){
        return 0.0f;
    }
    if (DEBUG_DOUBLE_LETTER) {
        AKLOGI("--- (%d, %d) double letter: start = %d, end = %d, dist = %d, time = %d,"
                " speed = %f, ave = %f, val = %f, start time = %d, end time = %d",
                id, (*sampledInputIndices)[id], start, end, beelineDistance, time,
                (static_cast<float>(beelineDistance) / static_cast<float>(time)), averageSpeed,
                ((static_cast<float>(beelineDistance) / static_cast<float>(time))
                        / averageSpeed), adjustedStartTime, adjustedEndTime);
    }
    // Offset 1%
    // TODO: Detect double letter more smartly
    return 0.01f + static_cast<float>(beelineDistance) / static_cast<float>(time) / averageSpeed;
}

/* static */ float ProximityInfoStateUtils::getPointAngle(
        const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs, const int index) {
    if (!sampledInputXs || !sampledInputYs) {
        return 0.0f;
    }
    const int sampledInputSize = sampledInputXs->size();
    if (index <= 0 || index >= sampledInputSize - 1) {
        return 0.0f;
    }
    const float previousDirection = getDirection(sampledInputXs, sampledInputYs, index - 1, index);
    const float nextDirection = getDirection(sampledInputXs, sampledInputYs, index, index + 1);
    const float directionDiff = getAngleDiff(previousDirection, nextDirection);
    return directionDiff;
}

/* static */ float ProximityInfoStateUtils::getPointsAngle(
        const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        const int index0, const int index1, const int index2) {
    if (!sampledInputXs || !sampledInputYs) {
        return 0.0f;
    }
    const int sampledInputSize = sampledInputXs->size();
    if (index0 < 0 || index0 > sampledInputSize - 1) {
        return 0.0f;
    }
    if (index1 < 0 || index1 > sampledInputSize - 1) {
        return 0.0f;
    }
    if (index2 < 0 || index2 > sampledInputSize - 1) {
        return 0.0f;
    }
    const float previousDirection = getDirection(sampledInputXs, sampledInputYs, index0, index1);
    const float nextDirection = getDirection(sampledInputXs, sampledInputYs, index1, index2);
    return getAngleDiff(previousDirection, nextDirection);
}

// TODO: Remove the "scale" parameter
// This function basically converts from a length to an edit distance. Accordingly, it's obviously
// wrong to compare with mMaxPointToKeyLength.
/* static */ float ProximityInfoStateUtils::getPointToKeyByIdLength(const float maxPointToKeyLength,
        const std::vector<float> *const SampledDistanceCache_G, const int keyCount,
        const int inputIndex, const int keyId, const float scale) {
    if (keyId != NOT_AN_INDEX) {
        const int index = inputIndex * keyCount + keyId;
        return min((*SampledDistanceCache_G)[index] * scale, maxPointToKeyLength);
    }
    // If the char is not a key on the keyboard then return the max length.
    return static_cast<float>(MAX_POINT_TO_KEY_LENGTH);
}

/* static */ float ProximityInfoStateUtils::getPointToKeyByIdLength(const float maxPointToKeyLength,
        const std::vector<float> *const SampledDistanceCache_G, const int keyCount,
        const int inputIndex, const int keyId) {
    return getPointToKeyByIdLength(
            maxPointToKeyLength, SampledDistanceCache_G, keyCount, inputIndex, keyId, 1.0f);
}

// Updates probabilities of aligning to some keys and skipping.
// Word suggestion should be based on this probabilities.
/* static */ void ProximityInfoStateUtils::updateAlignPointProbabilities(
        const float maxPointToKeyLength, const int mostCommonKeyWidth, const int keyCount,
        const int start, const int sampledInputSize, const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        const std::vector<float> *const sampledSpeedRates,
        const std::vector<int> *const sampledLengthCache,
        const std::vector<float> *const SampledDistanceCache_G,
        std::vector<NearKeycodesSet> *SampledNearKeysVector,
        std::vector<hash_map_compat<int, float> > *charProbabilities) {
    static const float MIN_PROBABILITY = 0.000001f;
    static const float MAX_SKIP_PROBABILITY = 0.95f;
    static const float SKIP_FIRST_POINT_PROBABILITY = 0.01f;
    static const float SKIP_LAST_POINT_PROBABILITY = 0.1f;
    static const float MIN_SPEED_RATE_FOR_SKIP_PROBABILITY = 0.15f;
    static const float SPEED_WEIGHT_FOR_SKIP_PROBABILITY = 0.9f;
    static const float SLOW_STRAIGHT_WEIGHT_FOR_SKIP_PROBABILITY = 0.6f;
    static const float NEAREST_DISTANCE_WEIGHT = 0.5f;
    static const float NEAREST_DISTANCE_BIAS = 0.5f;
    static const float NEAREST_DISTANCE_WEIGHT_FOR_LAST = 0.6f;
    static const float NEAREST_DISTANCE_BIAS_FOR_LAST = 0.4f;

    static const float ANGLE_WEIGHT = 0.90f;
    static const float DEEP_CORNER_ANGLE_THRESHOLD = M_PI_F * 60.0f / 180.0f;
    static const float SKIP_DEEP_CORNER_PROBABILITY = 0.1f;
    static const float CORNER_ANGLE_THRESHOLD = M_PI_F * 30.0f / 180.0f;
    static const float STRAIGHT_ANGLE_THRESHOLD = M_PI_F * 15.0f / 180.0f;
    static const float SKIP_CORNER_PROBABILITY = 0.4f;
    static const float SPEED_MARGIN = 0.1f;
    static const float CENTER_VALUE_OF_NORMALIZED_DISTRIBUTION = 0.0f;

    charProbabilities->resize(sampledInputSize);
    // Calculates probabilities of using a point as a correlated point with the character
    // for each point.
    for (int i = start; i < sampledInputSize; ++i) {
        (*charProbabilities)[i].clear();
        // First, calculates skip probability. Starts form MIN_SKIP_PROBABILITY.
        // Note that all values that are multiplied to this probability should be in [0.0, 1.0];
        float skipProbability = MAX_SKIP_PROBABILITY;

        const float currentAngle = getPointAngle(sampledInputXs, sampledInputYs, i);
        const float speedRate = (*sampledSpeedRates)[i];

        float nearestKeyDistance = static_cast<float>(MAX_POINT_TO_KEY_LENGTH);
        for (int j = 0; j < keyCount; ++j) {
            if ((*SampledNearKeysVector)[i].test(j)) {
                const float distance = getPointToKeyByIdLength(
                        maxPointToKeyLength, SampledDistanceCache_G, keyCount, i, j);
                if (distance < nearestKeyDistance) {
                    nearestKeyDistance = distance;
                }
            }
        }

        if (i == 0) {
            skipProbability *= min(1.0f, nearestKeyDistance * NEAREST_DISTANCE_WEIGHT
                    + NEAREST_DISTANCE_BIAS);
            // Promote the first point
            skipProbability *= SKIP_FIRST_POINT_PROBABILITY;
        } else if (i == sampledInputSize - 1) {
            skipProbability *= min(1.0f, nearestKeyDistance * NEAREST_DISTANCE_WEIGHT_FOR_LAST
                    + NEAREST_DISTANCE_BIAS_FOR_LAST);
            // Promote the last point
            skipProbability *= SKIP_LAST_POINT_PROBABILITY;
        } else {
            // If the current speed is relatively slower than adjacent keys, we promote this point.
            if ((*sampledSpeedRates)[i - 1] - SPEED_MARGIN > speedRate
                    && speedRate < (*sampledSpeedRates)[i + 1] - SPEED_MARGIN) {
                if (currentAngle < CORNER_ANGLE_THRESHOLD) {
                    skipProbability *= min(1.0f, speedRate
                            * SLOW_STRAIGHT_WEIGHT_FOR_SKIP_PROBABILITY);
                } else {
                    // If the angle is small enough, we promote this point more. (e.g. pit vs put)
                    skipProbability *= min(1.0f, speedRate * SPEED_WEIGHT_FOR_SKIP_PROBABILITY
                            + MIN_SPEED_RATE_FOR_SKIP_PROBABILITY);
                }
            }

            skipProbability *= min(1.0f, speedRate * nearestKeyDistance *
                    NEAREST_DISTANCE_WEIGHT + NEAREST_DISTANCE_BIAS);

            // Adjusts skip probability by a rate depending on angle.
            // ANGLE_RATE of skipProbability is adjusted by current angle.
            skipProbability *= (M_PI_F - currentAngle) / M_PI_F * ANGLE_WEIGHT
                    + (1.0f - ANGLE_WEIGHT);
            if (currentAngle > DEEP_CORNER_ANGLE_THRESHOLD) {
                skipProbability *= SKIP_DEEP_CORNER_PROBABILITY;
            }
            // We assume the angle of this point is the angle for point[i], point[i - 2]
            // and point[i - 3]. The reason why we don't use the angle for point[i], point[i - 1]
            // and point[i - 2] is this angle can be more affected by the noise.
            const float prevAngle = getPointsAngle(sampledInputXs, sampledInputYs, i, i - 2, i - 3);
            if (i >= 3 && prevAngle < STRAIGHT_ANGLE_THRESHOLD
                    && currentAngle > CORNER_ANGLE_THRESHOLD) {
                skipProbability *= SKIP_CORNER_PROBABILITY;
            }
        }

        // probabilities must be in [0.0, MAX_SKIP_PROBABILITY];
        ASSERT(skipProbability >= 0.0f);
        ASSERT(skipProbability <= MAX_SKIP_PROBABILITY);
        (*charProbabilities)[i][NOT_AN_INDEX] = skipProbability;

        // Second, calculates key probabilities by dividing the rest probability
        // (1.0f - skipProbability).
        const float inputCharProbability = 1.0f - skipProbability;

        // TODO: The variance is critical for accuracy; thus, adjusting these parameter by machine
        // learning or something would be efficient.
        static const float SPEEDxANGLE_WEIGHT_FOR_STANDARD_DIVIATION = 0.3f;
        static const float MAX_SPEEDxANGLE_RATE_FOR_STANDERD_DIVIATION = 0.25f;
        static const float SPEEDxNEAREST_WEIGHT_FOR_STANDARD_DIVIATION = 0.5f;
        static const float MAX_SPEEDxNEAREST_RATE_FOR_STANDERD_DIVIATION = 0.15f;
        static const float MIN_STANDERD_DIVIATION = 0.37f;

        const float speedxAngleRate = min(speedRate * currentAngle / M_PI_F
                * SPEEDxANGLE_WEIGHT_FOR_STANDARD_DIVIATION,
                        MAX_SPEEDxANGLE_RATE_FOR_STANDERD_DIVIATION);
        const float speedxNearestKeyDistanceRate = min(speedRate * nearestKeyDistance
                * SPEEDxNEAREST_WEIGHT_FOR_STANDARD_DIVIATION,
                        MAX_SPEEDxNEAREST_RATE_FOR_STANDERD_DIVIATION);
        const float sigma = speedxAngleRate + speedxNearestKeyDistanceRate + MIN_STANDERD_DIVIATION;

        ProximityInfoUtils::NormalDistribution
                distribution(CENTER_VALUE_OF_NORMALIZED_DISTRIBUTION, sigma);
        static const float PREV_DISTANCE_WEIGHT = 0.5f;
        static const float NEXT_DISTANCE_WEIGHT = 0.6f;
        // Summing up probability densities of all near keys.
        float sumOfProbabilityDensities = 0.0f;
        for (int j = 0; j < keyCount; ++j) {
            if ((*SampledNearKeysVector)[i].test(j)) {
                float distance = sqrtf(getPointToKeyByIdLength(
                        maxPointToKeyLength, SampledDistanceCache_G, keyCount, i, j));
                if (i == 0 && i != sampledInputSize - 1) {
                    // For the first point, weighted average of distances from first point and the
                    // next point to the key is used as a point to key distance.
                    const float nextDistance = sqrtf(getPointToKeyByIdLength(
                            maxPointToKeyLength, SampledDistanceCache_G, keyCount, i + 1, j));
                    if (nextDistance < distance) {
                        // The distance of the first point tends to bigger than continuing
                        // points because the first touch by the user can be sloppy.
                        // So we promote the first point if the distance of that point is larger
                        // than the distance of the next point.
                        distance = (distance + nextDistance * NEXT_DISTANCE_WEIGHT)
                                / (1.0f + NEXT_DISTANCE_WEIGHT);
                    }
                } else if (i != 0 && i == sampledInputSize - 1) {
                    // For the first point, weighted average of distances from last point and
                    // the previous point to the key is used as a point to key distance.
                    const float previousDistance = sqrtf(getPointToKeyByIdLength(
                            maxPointToKeyLength, SampledDistanceCache_G, keyCount, i - 1, j));
                    if (previousDistance < distance) {
                        // The distance of the last point tends to bigger than continuing points
                        // because the last touch by the user can be sloppy. So we promote the
                        // last point if the distance of that point is larger than the distance of
                        // the previous point.
                        distance = (distance + previousDistance * PREV_DISTANCE_WEIGHT)
                                / (1.0f + PREV_DISTANCE_WEIGHT);
                    }
                }
                // TODO: Promote the first point when the extended line from the next input is near
                // from a key. Also, promote the last point as well.
                sumOfProbabilityDensities += distribution.getProbabilityDensity(distance);
            }
        }

        // Split the probability of an input point to keys that are close to the input point.
        for (int j = 0; j < keyCount; ++j) {
            if ((*SampledNearKeysVector)[i].test(j)) {
                float distance = sqrtf(getPointToKeyByIdLength(
                        maxPointToKeyLength, SampledDistanceCache_G, keyCount, i, j));
                if (i == 0 && i != sampledInputSize - 1) {
                    // For the first point, weighted average of distances from the first point and
                    // the next point to the key is used as a point to key distance.
                    const float prevDistance = sqrtf(getPointToKeyByIdLength(
                            maxPointToKeyLength, SampledDistanceCache_G, keyCount, i + 1, j));
                    if (prevDistance < distance) {
                        distance = (distance + prevDistance * NEXT_DISTANCE_WEIGHT)
                                / (1.0f + NEXT_DISTANCE_WEIGHT);
                    }
                } else if (i != 0 && i == sampledInputSize - 1) {
                    // For the first point, weighted average of distances from last point and
                    // the previous point to the key is used as a point to key distance.
                    const float prevDistance = sqrtf(getPointToKeyByIdLength(
                            maxPointToKeyLength, SampledDistanceCache_G, keyCount, i - 1, j));
                    if (prevDistance < distance) {
                        distance = (distance + prevDistance * PREV_DISTANCE_WEIGHT)
                                / (1.0f + PREV_DISTANCE_WEIGHT);
                    }
                }
                const float probabilityDensity = distribution.getProbabilityDensity(distance);
                const float probability = inputCharProbability * probabilityDensity
                        / sumOfProbabilityDensities;
                (*charProbabilities)[i][j] = probability;
            }
        }
    }

    if (DEBUG_POINTS_PROBABILITY) {
        for (int i = 0; i < sampledInputSize; ++i) {
            std::stringstream sstream;
            sstream << i << ", ";
            sstream << "(" << (*sampledInputXs)[i] << ", " << (*sampledInputYs)[i] << "), ";
            sstream << "Speed: "<< (*sampledSpeedRates)[i] << ", ";
            sstream << "Angle: "<< getPointAngle(sampledInputXs, sampledInputYs, i) << ", \n";

            for (hash_map_compat<int, float>::iterator it = (*charProbabilities)[i].begin();
                    it != (*charProbabilities)[i].end(); ++it) {
                if (it->first == NOT_AN_INDEX) {
                    sstream << it->first
                            << "(skip):"
                            << it->second
                            << "\n";
                } else {
                    sstream << it->first
                            << "("
                            //<< static_cast<char>(mProximityInfo->getCodePointOf(it->first))
                            << "):"
                            << it->second
                            << "\n";
                }
            }
            AKLOGI("%s", sstream.str().c_str());
        }
    }

    // Decrease key probabilities of points which don't have the highest probability of that key
    // among nearby points. Probabilities of the first point and the last point are not suppressed.
    for (int i = max(start, 1); i < sampledInputSize; ++i) {
        for (int j = i + 1; j < sampledInputSize; ++j) {
            if (!suppressCharProbabilities(
                    mostCommonKeyWidth, sampledInputSize, sampledLengthCache, i, j,
                    charProbabilities)) {
                break;
            }
        }
        for (int j = i - 1; j >= max(start, 0); --j) {
            if (!suppressCharProbabilities(
                    mostCommonKeyWidth, sampledInputSize, sampledLengthCache, i, j,
                    charProbabilities)) {
                break;
            }
        }
    }

    // Converting from raw probabilities to log probabilities to calculate spatial distance.
    for (int i = start; i < sampledInputSize; ++i) {
        for (int j = 0; j < keyCount; ++j) {
            hash_map_compat<int, float>::iterator it = (*charProbabilities)[i].find(j);
            if (it == (*charProbabilities)[i].end()){
                (*SampledNearKeysVector)[i].reset(j);
            } else if(it->second < MIN_PROBABILITY) {
                // Erases from near keys vector because it has very low probability.
                (*SampledNearKeysVector)[i].reset(j);
                (*charProbabilities)[i].erase(j);
            } else {
                it->second = -logf(it->second);
            }
        }
        (*charProbabilities)[i][NOT_AN_INDEX] = -logf((*charProbabilities)[i][NOT_AN_INDEX]);
    }
}

/* static */ void ProximityInfoStateUtils::updateSampledSearchKeysVector(
        const ProximityInfo *const proximityInfo, const int sampledInputSize,
        const int lastSavedInputSize,
        const std::vector<int> *const sampledLengthCache,
        const std::vector<NearKeycodesSet> *const SampledNearKeysVector,
        std::vector<NearKeycodesSet> *sampledSearchKeysVector) {
    sampledSearchKeysVector->resize(sampledInputSize);
    const int readForwordLength = static_cast<int>(
            hypotf(proximityInfo->getKeyboardWidth(), proximityInfo->getKeyboardHeight())
                    * ProximityInfoParams::SEARCH_KEY_RADIUS_RATIO);
    for (int i = 0; i < sampledInputSize; ++i) {
        if (i >= lastSavedInputSize) {
            (*sampledSearchKeysVector)[i].reset();
        }
        for (int j = max(i, lastSavedInputSize); j < sampledInputSize; ++j) {
            // TODO: Investigate if this is required. This may not fail.
            if ((*sampledLengthCache)[j] - (*sampledLengthCache)[i] >= readForwordLength) {
                break;
            }
            (*sampledSearchKeysVector)[i] |= (*SampledNearKeysVector)[j];
        }
    }
}

// Decreases char probabilities of index0 by checking probabilities of a near point (index1) and
// increases char probabilities of index1 by checking probabilities of index0.
/* static */ bool ProximityInfoStateUtils::suppressCharProbabilities(const int mostCommonKeyWidth,
        const int sampledInputSize, const std::vector<int> *const lengthCache,
        const int index0, const int index1,
        std::vector<hash_map_compat<int, float> > *charProbabilities) {
    ASSERT(0 <= index0 && index0 < sampledInputSize);
    ASSERT(0 <= index1 && index1 < sampledInputSize);

    static const float SUPPRESSION_LENGTH_WEIGHT = 1.5f;
    static const float MIN_SUPPRESSION_RATE = 0.1f;
    static const float SUPPRESSION_WEIGHT = 0.5f;
    static const float SUPPRESSION_WEIGHT_FOR_PROBABILITY_GAIN = 0.1f;
    static const float SKIP_PROBABALITY_WEIGHT_FOR_PROBABILITY_GAIN = 0.3f;

    const float keyWidthFloat = static_cast<float>(mostCommonKeyWidth);
    const float diff = fabsf(static_cast<float>((*lengthCache)[index0] - (*lengthCache)[index1]));
    if (diff > keyWidthFloat * SUPPRESSION_LENGTH_WEIGHT) {
        return false;
    }
    const float suppressionRate = MIN_SUPPRESSION_RATE
            + diff / keyWidthFloat / SUPPRESSION_LENGTH_WEIGHT * SUPPRESSION_WEIGHT;
    for (hash_map_compat<int, float>::iterator it = (*charProbabilities)[index0].begin();
            it != (*charProbabilities)[index0].end(); ++it) {
        hash_map_compat<int, float>::iterator it2 =  (*charProbabilities)[index1].find(it->first);
        if (it2 != (*charProbabilities)[index1].end() && it->second < it2->second) {
            const float newProbability = it->second * suppressionRate;
            const float suppression = it->second - newProbability;
            it->second = newProbability;
            // mCharProbabilities[index0][NOT_AN_INDEX] is the probability of skipping this point.
            (*charProbabilities)[index0][NOT_AN_INDEX] += suppression;

            // Add the probability of the same key nearby index1
            const float probabilityGain = min(suppression * SUPPRESSION_WEIGHT_FOR_PROBABILITY_GAIN,
                    (*charProbabilities)[index1][NOT_AN_INDEX]
                            * SKIP_PROBABALITY_WEIGHT_FOR_PROBABILITY_GAIN);
            it2->second += probabilityGain;
            (*charProbabilities)[index1][NOT_AN_INDEX] -= probabilityGain;
        }
    }
    return true;
}

/* static */ bool ProximityInfoStateUtils::checkAndReturnIsContinuationPossible(const int inputSize,
        const int *const xCoordinates, const int *const yCoordinates, const int *const times,
        const int sampledInputSize, const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        const std::vector<int> *const sampledTimes,
        const std::vector<int> *const sampledInputIndices) {
    if (inputSize < sampledInputSize) {
        return false;
    }
    for (int i = 0; i < sampledInputSize; ++i) {
        const int index = (*sampledInputIndices)[i];
        if (index >= inputSize) {
            return false;
        }
        if (xCoordinates[index] != (*sampledInputXs)[i]
                || yCoordinates[index] != (*sampledInputYs)[i]) {
            return false;
        }
        if (!times) {
            continue;
        }
        if (times[index] != (*sampledTimes)[i]) {
            return false;
        }
    }
    return true;
}

// Get a word that is detected by tracing the most probable string into codePointBuf and
// returns probability of generating the word.
/* static */ float ProximityInfoStateUtils::getMostProbableString(
        const ProximityInfo *const proximityInfo, const int sampledInputSize,
        const std::vector<hash_map_compat<int, float> > *const charProbabilities,
        int *const codePointBuf) {
    ASSERT(charProbabilities->size() >= 0 && sampledInputSize >= 0);
    memset(codePointBuf, 0, sizeof(codePointBuf[0]) * MAX_WORD_LENGTH);
    static const float DEMOTION_LOG_PROBABILITY = 0.3f;
    int index = 0;
    float sumLogProbability = 0.0f;
    // TODO: Current implementation is greedy algorithm. DP would be efficient for many cases.
    for (int i = 0; i < sampledInputSize && index < MAX_WORD_LENGTH - 1; ++i) {
        float minLogProbability = static_cast<float>(MAX_POINT_TO_KEY_LENGTH);
        int character = NOT_AN_INDEX;
        for (hash_map_compat<int, float>::const_iterator it = (*charProbabilities)[i].begin();
                it != (*charProbabilities)[i].end(); ++it) {
            const float logProbability = (it->first != NOT_AN_INDEX)
                    ? it->second + DEMOTION_LOG_PROBABILITY : it->second;
            if (logProbability < minLogProbability) {
                minLogProbability = logProbability;
                character = it->first;
            }
        }
        if (character != NOT_AN_INDEX) {
            codePointBuf[index] = proximityInfo->getCodePointOf(character);
            index++;
        }
        sumLogProbability += minLogProbability;
    }
    codePointBuf[index] = '\0';
    return sumLogProbability;
}

/* static */ void ProximityInfoStateUtils::dump(const bool isGeometric, const int inputSize,
        const int *const inputXCoordinates, const int *const inputYCoordinates,
        const int sampledInputSize, const std::vector<int> *const sampledInputXs,
        const std::vector<int> *const sampledInputYs,
        const std::vector<int> *const sampledTimes,
        const std::vector<float> *const sampledSpeedRates,
        const std::vector<int> *const sampledBeelineSpeedPercentiles) {
    if (DEBUG_GEO_FULL) {
        for (int i = 0; i < sampledInputSize; ++i) {
            AKLOGI("Sampled(%d): x = %d, y = %d, time = %d", i, (*sampledInputXs)[i],
                    (*sampledInputYs)[i], sampledTimes ? (*sampledTimes)[i] : -1);
        }
    }

    std::stringstream originalX, originalY, sampledX, sampledY;
    for (int i = 0; i < inputSize; ++i) {
        originalX << inputXCoordinates[i];
        originalY << inputYCoordinates[i];
        if (i != inputSize - 1) {
            originalX << ";";
            originalY << ";";
        }
    }
    AKLOGI("===== sampled points =====");
    for (int i = 0; i < sampledInputSize; ++i) {
        if (isGeometric) {
            AKLOGI("%d: x = %d, y = %d, time = %d, relative speed = %.4f, beeline speed = %d",
                    i, (*sampledInputXs)[i], (*sampledInputYs)[i], (*sampledTimes)[i],
                    (*sampledSpeedRates)[i], (*sampledBeelineSpeedPercentiles)[i]);
        }
        sampledX << (*sampledInputXs)[i];
        sampledY << (*sampledInputYs)[i];
        if (i != sampledInputSize - 1) {
            sampledX << ";";
            sampledY << ";";
        }
    }
    AKLOGI("original points:\n%s, %s,\nsampled points:\n%s, %s,\n",
            originalX.str().c_str(), originalY.str().c_str(), sampledX.str().c_str(),
            sampledY.str().c_str());
}
} // namespace latinime