Has the clustering illusion been removed?

[Jeremiah]

I was playing a recent trunk version and was surprised to find that certain items and monsters appeared to be generated with roughly the same frequency as in previous versions of Crawl.

Just wondering if the devs have removed or nerfed the clustering illusion. If so, this is a terrible move that will surely only make the Tavern better for experienced players, who will no longer have to keep pointing out the existence of the clustering illusion in the forums.

[nicolae]

There've been no changes made to the clustering illusion in trunk, it's just your overzealous pattern recognition.

[variouselite]

but I just found 3 identical +3 robes in the same store. rng is broken!! (make sure my name gets credit for this bug pls)

[Grimm]

god of clustering illusion

[MDvedh]

Does crawl has PRNG with a good source of entropy? Because if it hasn't, It becomes tedious-but-optimal play style where you have to decypher your rng to know what's the next roll and that's obviously against the game philosophy.

[reaver]

Hi,

I wrote the current version of the random number generator to replace Mersenne Twister because a player figured out how to predict the state. In general writing a random number generator is a very bad idea. If you doubt me look at java.lang.Random.

The generator is seeded from the system's pseudorandom number generator, combining that output with the current system time and process id.

The generator has a 160-bit internal state. This is a very large state. For those keeping score at home, there are approximately 2^190 atoms in the sun.

The design is based on combining JKISS, a non-cryptographic RNG, with an alternating step generator (ASG).

JKISS works by jamming together three different so-so RNGs: one linear congruential generator (LCG), a multiply-with-carry generator (MWC) and a xorshift generator. I have slightly modified JKISS to make it resistant to the types of cryptanalysis that a crawl player might attempt.

An ASG works by combining the output from two independent generators and alternatively advancing them based on the output of a third 'gate' generator. In this case, I use a 32-bit Galois Linear Feedback Shift Register as the gate and advance a xorshift generator or a MWC generator. The output of these generators is combined is with an LCG.

This generator passes L'Ecuyer's TestU01 Big Crush suite and Marsaglia's Diehard suite. Mersenne Twister fails two of the tests in this suite.

As others have said, crawl is pretty darn random.

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[variouselite]

Seems passable.

[Hirsch I]

for some reason I thought Clustering Illusion was a monster spell. maybe one of mara's. I think I should get some sleep.

[MyOtheHedgeFox]

I thought it was about greater liches summoned by greater liches summoned by greater liches summoned by greater liches.