Assignment 3

Daraban Albert-Timotei

Main Logic

• Create custom MPI datatype for more efficient communication.
• Start tracker or peer logic depending on rank.

Tracker Logic

• Initialize data structures:
  • Array of finished peers (1 at the index of the rank of a peer means that the peer has finished).
  • Swarm array (swarm structure).
• Receive information about which files each peer has.
• Pass through a barrier to signal that file sharing can begin.
• Loop until all peers finish sharing. In this loop, the tracker receives 4 types of messages:
  • Request for information about a file and its peers.
  • Update about a newly downloaded chunk of a peer.
  • Signal that a peer finished downloading a whole file.
  • Signal that a peer finished all files it wanted.

Peer Logic

• Send info about the files the peer has.
• Pass through a barrier to signal that it's ready to start sharing.
• Start two threads, one for download logic and the other for upload logic.

Upload Logic

• Loop until all peers finish sharing. In this loop, the peer receives 2 types of messages:
  • Request for a chunk from a fellow peer.
  • Message from the tracker that all files finished sharing.

Download Logic

• Initialize data structures:
  • Array of ints corresponding to each file to be downloaded, containing the rank of the last peer used to get a chunk from. This is used to distribute the load to other potential peers.
  • Array of ints specifying if a file was fully downloaded.
  • 3-dimensional array to hold for each chunk of a file, which peers have it.
• Loop until finish downloading everything. In this loop, do the following:
  • Get information about wanted files.
  • Download a number of chunks from peers. If after download we have all wanted files, stop the loop.
  • Send info about what chunks it has.