RE: [Cse461] Emulator works but simulator hangs

From: Jeff Tyrrill (mail_at_jeff-tyrrill.com)
Date: Wed Feb 04 2004 - 12:55:00 PST

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    We figured out the problem. There was an infinite send loop in our code (our
    code for checking sequence numbers had a problem). This caused a huge excess
    of flooded (broadcast) packets, which overflowed the simulator but not the
    emulator. (It turns out our code wasn't working "perfectly" in the emulator
    either, but worked somewhat.)

    -----Original Message-----
    From: cse461-bounces_at_cs.washington.edu
    [mailto:cse461-bounces_at_cs.washington.edu]On Behalf Of Janet Davis
    Sent: 2004 February 04, Wednesday 12:28
    To: Jeff Tyrrill
    Cc: cse461_at_cs.washington.edu
    Subject: Re: [Cse461] Emulator works but simulator hangs

    On Tue, 3 Feb 2004, Jeff Tyrrill wrote:

    > We have our project working in the emulator including on the class
    trawler,
    > but in the simulator, there is a problem. We specify the number of nodes
    and
    > a topology file, and it starts, and some of the nodes see each other as
    > neighbors, but everything sort of freezes after that. Apparently, timers
    > never get called. Also, CPU usage goes up to maximum. We can enter
    commands
    > and the code for our onCommand runs, but it's not much use because
    neighbor
    > discovery and link state packets don't get sent.
    >
    > Are there some things we should check? Does this just indicate a problem
    in
    > our code? Again, everything works perfectly in emulation mode, so we're
    not
    > sure what to check for.

    I'm honestly not sure. Here are some things you might look at:

    - Are you calling addTimer in the node constructor or in start()?

    - If you hit ^C, what is the stack trace? Is it possible you are
    forwarding a packet you received from yourself?

    - What's your OS, ruby version, etc?

    Has anyone else seen a similar problem?

    (By the way, you are welcome to use the emulator for the turn-in output.)

    Cheers,
    Janet

    --
    Janet Davis
    jlnd_at_cs.washington.edu
    http://www.cs.washington.edu/homes/jlnd/
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