18.337 WebMeeting

Message from: B Bartley (bbartley@MIT.EDU)
About: Latency/Throughput (Was: Clarification for Graphs on HW1)

Wed, 19 Feb 97 01:20:36 EST

  • Next message: Kris Joshi: "mpirun -np 2 -machinename hosts <program> doesn't always work"
    Latency is how long it takes the beginning of a message to get from the starting point to the ending point.

    Throughput is how many bits come out of the line of communication in a given amount of time.

    For instance, if you have an optical fiber 10 light seconds long and you put one bit per second into one end of it, it'll be 10 seconds before the first bit makes it out the other end (assuming light goes c in an optical fiber, or a clever definition of "light second") but once the bits start coming out they'll do so one per second. So you have a 10 second latency, but 1 bit/second throughput.

    If you double the length of the fiber you double the latency but throughput is unchanged.

    Brad
    .
    ----
    NOTE: This message was sent using a WWW form. The address bbartley@mit.edu
    was typed manually, and may easily be incorrect.

    You may post a follow-up message or a new message. To send a reply directly to the author, you may click on the email address above.

    If you would like to submit a message using your own mail program, send it to: 18.337-wm@webmeet.mit.edu

    If you are following up this article, please include the following line at the beginning of your message: 
    In-Reply-To: 9702190620.AA06537@arachnophobia.MIT.EDU