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Whose Bug Is This Anyway?

Posted by Soulskill on from the it's-nobody's-fault-and-everybody's-angry dept.

An anonymous reader writes "Patrick Wyatt, one of the developers behind the original Warcraft and StarCraft games, as well as Diablo and Guild Wars, has a post about some of the bug hunting he's done throughout his career. He covers familiar topics — crunch time leading to stupid mistakes and finding bugs in compilers rather than game code — and shares a story about finding a way to diagnose hardware failure for players of Guild Wars. Quoting: '[Mike O'Brien] wrote a module ("OsStress") which would allocate a block of memory, perform calculations in that memory block, and then compare the results of the calculation to a table of known answers. He encoded this stress-test into the main game loop so that the computer would perform this verification step about 30-50 times per second. On a properly functioning computer this stress test should never fail, but surprisingly we discovered that on about 1% of the computers being used to play Guild Wars it did fail! One percent might not sound like a big deal, but when one million gamers play the game on any given day that means 10,000 would have at least one crash bug. Our programming team could spend weeks researching the bugs for just one day at that rate!'"

5 of 241 comments (clear)

  1. The memory thing... by Loopy · · Score: 5, Informative

    ...is pretty much what those of us that build our own systems do anytime we upgrade components (RAM/CPU/MB) or experience unexplained errors. It's similar to running the Prime95 torture tests overnight, which also checks calculations in memory against known data sets for expected values.

    Good stuff for those that don't already have a knack for QA.

    1. Re:The memory thing... by DMUTPeregrine · · Score: 5, Informative

      Unless you're trying to overclock.
      Admittedly that's a small percentage of the populace, even among people who build their own systems.

      --
      Not a sentence!
    2. Re:The memory thing... by Alwin+Henseler · · Score: 5, Informative

      The defect rate on hardware is so low you don't need to - buy your stuff from Newegg, assemble, and install. Either it's DOA or runs forever.

      Look up "bathtub curve" sometime. Even well-built, perfectly working gear is aging, aging usually translates into "reduced performance / reliability", and any electronic part will fail sometime. Possibly gradually. Especially the just-makes-it-past-warranty crap that's sold these days. And there may be instabilities / incompatibilities that only show under very specific conditions (like when a system is pushed really hard).

      That's ignoring things like ambient temperature variations, CPU coolers clogging with dust over the years, sporadic contact problems on connectors, or the odd cosmic ray that nukes a bit in RAM (yes that happens, too). A lot of things must come together to have (and keep) a reliable working computer, so a lot of things can go wrong and put an end to that.

  2. OsStress by larry+bagina · · Score: 5, Informative

    Microsoft found similar impossible bugs when overclocking was involved.

    --
    Do you even lift?

    These aren't the 'roids you're looking for.

  3. Re:Reminded me of my first C application by richardcavell · · Score: 5, Informative

    I just want to correct this, not to prove how smart I am but because there are novice programmers out there who will learn from this case. The statement:

    if (i = 1) {

    is equivalent to:

    i = 1; /* correction */
    if (i) {