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ViewSubsampler.cpp

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#include "ViewSubsampler.h"

#include <fcntl.h> // for open()
#include <cerrno> // for errno
#include <cstdio> // for perror()

#define RETRY_TIME_SECONDS 2
#define MAX_GOOD_MATCH_POS 10

int VWCompare(const void* elem1, const void* elem2 )
{
        const double& w1 = ((const VIEWWEIGHT*)elem1)->dVoteWeight;
        const double& w2 = ((const VIEWWEIGHT*)elem2)->dVoteWeight;
        
        return w1 == w2 ? 0:(w1 < w2 ? 1:-1);
}

bool LockFile::Lock(const char* szLockFileName, unsigned int nSleepTime)
{
        while (true)
    {
                fd = open(szLockFileName, O_WRONLY | O_CREAT | O_EXCL);
                
                if (fd < 0 && errno == EEXIST)
                        sleep(nSleepTime); // the file already exist; another process is holding the lock
                else if (fd < 0)
                {
                        perror("locking failed for the following reason");
                        return m_bLocked = false;
                }
                else
                        break;
        }

     // if we got here, we own the lock
     m_strFileName = szLockFileName;
     return m_bLocked = true;
}

void LockFile::Unlock()
{
        if (m_bLocked)
        {
                remove(m_strFileName);
                close(fd);
                m_bLocked = false;
        }
}

void ViewSubsampler::AddViewWeights(int nViewsPerObject, const DAG* pQueryDag,
        const leda_array<MatchInfo>& matchList, const SmartArray<int>& neigViews, int kBest)
{
        SmartArray<int> viewPos(nViewsPerObject);
        Record rec;
        VIEWWEIGHT vw;
        int i;
        
        rec.nIndexedWithKBest = kBest;
        rec.strObjName = pQueryDag->GetObjName();       
        viewPos.Set(kBest);
        const int nViewNum = pQueryDag->GetViewNumber();
        
        // Collect from the matching list all the views of a given object.
        for (i = 0; i < matchList.size(); i++)
        {
                const DAGPtr ptrDag = matchList[i].ptrDAG;
                
                // Stop searching when null ptr is reached
                if (ptrDag.IsNull())
                        break;
        
                // if it's a view of the target obj, save its position
                if (rec.strObjName == ptrDag->GetObjName())
                {
                        viewPos[ptrDag->GetViewNumber() - 1] = i;
                        
                        // let's also add views that help for object recognition with negative position
                        if (nViewNum != ptrDag->GetViewNumber() && i < MAX_GOOD_MATCH_POS)
                        {
                                vw.nViewNumber = ptrDag->GetViewNumber();
                                vw.nViewRankPos = -i - 1; //-1 to avoid 0
                                vw.dVoteWeight = CompVoteWeight(vw.nViewRankPos, kBest);
                                rec.bmviews.AddTail(vw);
                        }
                }
        }
        
        // Check the ranking of the neghbouring views
        // and compute a vote according to it.
        for (i = 0; i < neigViews.GetSize(); i++)
        {
                vw.nViewNumber = neigViews[i];
                vw.nViewRankPos = viewPos[vw.nViewNumber - 1];          
                vw.dVoteWeight = CompVoteWeight(vw.nViewRankPos, kBest);
        rec.bmviews.AddTail(vw);
        }

        m_viewVotes.append(rec);
}

void ViewSubsampler::SaveViewWeights(const char* szDataFileName)
{
        LockFile lockfile;
        
        // Proteck the writting operation from multiple-processes conflict
        if (!lockfile.Lock("lockfile.lck", RETRY_TIME_SECONDS))
        {
                cerr << "\nCan't lock 'lockfile.lck'. Job is cancelled" << endl;
                exit(1);
        }
        
        fstream outfile(szDataFileName, ios::out | ios::app);
        leda_list_item it;
        
        forall_items(it, m_viewVotes)
                m_viewVotes[it].Write(outfile);
        
        outfile.close();
        
        lockfile.Unlock();
}

bool ViewSubsampler::RetrieveViewWeights(const char* szDataFileName, int nViewsPerObject, bool bRankByObject)
{
        ObjViewArray objs;
        Record rec;
        int i;
        
        fstream infile(szDataFileName, ios::in);
        
        if (infile.fail())
                return false;
                
        cerr << "Retriving subsampling info from " << szDataFileName << endl;

        while (!infile.eof())
        {
                rec.Read(infile);
                                
                // if it's the first time we see the obj name, prepare the array
                if (!objs.defined((const char*)rec.strObjName))
                {
                        VWArray& cumVotes = objs[(const char*)rec.strObjName];
                        cumVotes.ReSize(nViewsPerObject);
                        
                        for (i = 0; i < nViewsPerObject; i++)
                                cumVotes[i].nViewNumber = i + 1;
                }
                
                // for all the views associated to the obj, add their vote to the unsorted-vote array
                for (i = 0; i < rec.bmviews.GetSize(); i++)             
                {
                        VWArray& cumVotes = objs[(const char*)rec.strObjName];
                        VIEWWEIGHT& vw = rec.bmviews[i];
                        VIEWWEIGHT& cumVote = cumVotes[vw.nViewNumber - 1];
                                
                        ASSERT(cumVote.nViewNumber == vw.nViewNumber);
                        cumVote.dVoteWeight += CompVoteWeight(vw.nViewRankPos, rec.nIndexedWithKBest); //vw.dVoteWeight
                }
        }
        
        leda_string strKey;
        
        // Sort views by object name or by their overall position
        if (bRankByObject)
        {
        forall_defined(strKey, objs)
        {
                VWArray& cumVotes = objs[strKey];
                cumVotes.Sort(VWCompare);
                
                VWArray& ranViews = m_rankedObjViews[strKey];
                ranViews.ReSize(nViewsPerObject);
                
                for (i = 0; i < cumVotes.GetSize(); i++)
                {
                        VIEWWEIGHT& vw = cumVotes[i];
                        
                        ranViews[vw.nViewNumber - 1].nViewRankPos = i;
                        ranViews[vw.nViewNumber - 1].dVoteWeight = vw.dVoteWeight;
                }
        }
    }
    else
    {
        SmartArray<OBJVIEWWEIGHT> ovws(objs.size() * nViewsPerObject);
        int j = 0;
        
        // collect all the votes in a sigle array and assoc each one to
        // the corresponding obj name
        forall_defined(strKey, objs)
        {
                m_rankedObjViews[strKey].ReSize(nViewsPerObject);
                VWArray& cumVotes = objs[strKey];
                String strObjName((const char*)strKey);
                
                for (i = 0; i < cumVotes.GetSize(); i++, j++)
                        ovws[j].Set(strObjName, cumVotes[i]);
        }

        ovws.Sort(VWCompare);
        
        for (i = 0; i < ovws.GetSize(); i++)
        {
                OBJVIEWWEIGHT& vw = ovws[i];
                VWArray& ranViews = m_rankedObjViews[(const char*)vw.strObjName];
                        
                ranViews[vw.nViewNumber - 1].nViewRankPos = i;
                ranViews[vw.nViewNumber - 1].dVoteWeight = vw.dVoteWeight;
        }
    }
        
        return true;
}

double ViewSubsampler::CompVoteWeight(int nPos, int kBest) const
{
        double w;
        
        if (nPos >= 0)
        {
        if (nPos < 9)
                w = 0.0;
        /*else if (nPos < 30)
                w = 1;
        else if (nPos < kBest)
                w = 1.5;
        else
                w = 2;*/
        else
                w = 1 + double(nPos) / double(kBest);
        }
        else
        {
                // nPos goes from -1 to -MAX_GOOD_MATCH_POS
                nPos = -nPos - 1; //make it positive, to simplify reading the eq.
                
                // if its well ranked, we want a negative weight, so that is a reward
                if (nPos < 4)
                        w = -2 + (double(nPos) / double(3));
                else
                        w = 0.0;
        }
                
        return w;
}

int RandInRange(int a, int b)
{
        return (int)(a + (1 + b-a )*(double)rand()/(RAND_MAX+1.0));
}

SmartArray<int> ViewSubsampler::RandomSubsampling(int nCurViewNum, int nNewViewNum)
{
        SmartArray<int> viewToRem(nCurViewNum);
        leda_list<int> list;
        leda_list_item it;

        ASSERT(nCurViewNum > nNewViewNum);

        viewToRem.Set(0);

        for (int i = 0; i < nCurViewNum; i++)
                list.push(i);
        
        srand((unsigned) time(NULL));

        while (list.size() != nNewViewNum)
        {
                it = list.get_item(RandInRange(0, list.size() - 1));
                viewToRem[list[it]] = 1;
                list.del_item(it);
        }

        return viewToRem;
}

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