I made a small "else" in the selection of chunks to download, after some testing i found a significant speedup when reach the last third of the download.

downloader.cpp
void Downloader::downloadFrom(PeerDownloader* pd)

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if (chunk_selector->select(pd,chunk))
{
   :
   :
}
else {
  // The peer has nothing more - start asking him for the
  // chunks we current downloads that he has.
  for (CurChunkItr j = current_chunks.begin();j != current_chunks.end();++j)
  {
    ChunkDownload* cd = j->second;            
    if (pd->hasChunk(cd->getChunk()->getIndex()))
      cd->assignPeer(pd,true);
  }
}


I'll test it out, see if it doesn't have any unintended side affects.

I added the changes, with some small modifications.

OK, thats better.


I had used break instead of return, if someone in the future add something at the end of the function....., but for now return works just fine.

No, that wasn't bettter!
If more then 1 peer is in the same situation all peers got requests of the same chunk, I modified the else little!

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      else
      {
         // If the peer hasn't got a chunk we want,
         // try to assign it to a chunk we are currently downloading
         ChunkDownload *cdmin=NULL;
         for (CurChunkItr j = current_chunks.begin();j != current_chunks.end();++j)
         {
            ChunkDownload* cd = j->second;
            if (pd->hasChunk(cd->getChunk()->getIndex()))
            {
               if (cd->containsPeer(pd))
                  continue;
               if (cdmin==NULL)
                  cdmin=cd;
               else if (cd->getNumDownloaders()<cdmin->getNumDownloaders())
                  cdmin=cd;

            }
         }
         if (cdmin)
            cdmin->assignPeer(pd,true);
      }


And added one function to ChunkDownload (chunkdownload.h)

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bool containsPeer(PeerDownloader *pd) {return pdown.contains(pd);}


Thats a bit fairer indeed, I will add it with my next commit.