Issue downloading 1TB Torrent

[ieee8023]

This torrent seems to not download correctly. There is high CPU usage, it crashes the kernel on colab, it doesn't seem to download from webseeds, and the download is only around 30kB/s.

7967a1633f7f89d3035838067a40cd807d935b3d

[mweiss17]

In the latest version (2.1.14) I get a rate above 1 megabyte per second from that peer. It's still too slow (we should theoretically get 10-15).

I believe that slowness is coming in large part from the large number of pieces that this torrent has (over 250k), which slows down some operations. For example, I often call a function to check if we have finished downloading the torrent.

        if sum(self.bitfield) == self.number_of_pieces:
            return True
        return False

When that bitfield is 250,000 bits, it takes roughly 2.5 seconds to calculate the sum. I'll change it to a numpy array, which is easy, but there are several other computations like that to speed up.