Greater Vault Frequency

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  • d_m
    Angband Devteam member
    • Aug 2008
    • 1517

    Greater Vault Frequency

    I just wanted to share some observations about room frequency, etc. to see if they seem consistent with people's observations.

    The following chart breaks down probabilities that the first room of a dungeon is of a particular type by percentage (so 1.2 is 1.2%): http://www.bearhome.net/erik/room-gen.txt. In theory these percentages work for each of the 50 rooms being tried, but in practice the probabilities shift due to lack of space for larger rooms (particularly greater vaults). I computed these numbers by reading the code and doing a little bit of basic statistics.

    Due to the complexity of measuring the probability that a particular level would have a particular room type, I decided to resort to dynamic analysis. After collecting a bunch of data via debug mode it seems like the probability for a particular level to have a greater vault is roughly equal to the percentage chance that the first room will be a greater vault at that depth times 10. That is:

    Code:
    0:    0%
    10:  <1%
    20:   1%
    30:   2%
    40:   4%
    50:   6%
    60:   9%
    70:  12%
    80:  16%
    90:  20%
    100: 25%
    This might be a little generous... using x8 or x9 as a multiplier might be a slightly better fit but x10 was easy to compute for this post. Does this square with people's general experience or beliefs?

    Fair warning: I'm not necessarily committed to attempting to maintain the exact distribution of all room types in possible generation refactors... but since greater vaults are an important/fun part of the game, it seemed like a good thing to measure before and after.
    Last edited by d_m; September 17, 2009, 06:18.
    linux->xterm->screen->pmacs
  • Pete Mack
    Prophet
    • Apr 2007
    • 6883

    #2
    This is a case where bootstrap simulation will trump calculations, any day...

    Comment

    • PowerDiver
      Prophet
      • Mar 2008
      • 2820

      #3
      Originally posted by d_m
      After collecting a bunch of data via debug mode it seems like the probability for a particular level to have a greater vault is roughly equal to the percentage chance that the first room will be a greater vault at that depth times 10.
      I would have guessed much less than 10x, maybe 6x but surely your stats are better than my guesses.

      OTOH, vaults have different sizes. Does that matter in the placement? If so, seeing how much it changes for the largest vaults would be of interest.

      Were your experiments on a fixed dungeon size, or the random sizes currently in 3.1.2? It would not surprise me for significantly different behavior on an 80%x80% level.

      Comment

      • d_m
        Angband Devteam member
        • Aug 2008
        • 1517

        #4
        Originally posted by PowerDiver
        I would have guessed much less than 10x, maybe 6x but surely your stats are better than my guesses.

        OTOH, vaults have different sizes. Does that matter in the placement? If so, seeing how much it changes for the largest vaults would be of interest.

        Were your experiments on a fixed dungeon size, or the random sizes currently in 3.1.2? It would not surprise me for significantly different behavior on an 80%x80% level.
        I'm pretty sure that no matter which vault will end up being placed, it checks to make sure there is enough space to accommodate the largest vault. I did these experiments on a full-size dungeon, hard-coding the scaling factor to 100%. I think you're right that smaller dungeons will get greater vaults much less frequently.
        linux->xterm->screen->pmacs

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