Random number generation?

[Chud]

I think with the current display where probability of failing is shown outright, it would be better to reexamine this mindset.

I have to agree here -- especially given that all the hardware Angband is going to be running on these days is so much faster than the earliest versions needed to work with; implementing a computationally expensive (relatively) RNG is no longer a practical problem.

Or maybe it never was; I haven't looked at how fast the various RNG algorithms are these days--maybe this was never an issue, but in any case it can't possibly be today. And I'd really rather that a given percent chance was honestly presented in the game, if it's going to be presented at all. Bugginess to the contrary might add some character to the game, but in my opinion it's not the sort of character the game wants.

[fizzix]

Angband's RNG is far far less random then MT. We could change it, but it always seemed to be part of the character of the game to me.

I think with the current display where probability of failing is shown outright, it would be better to reexamine this mindset.

For example, a lot of times I make a calculation assuming independent events. I might say, I have a 5% chance of failing, so my chances of failing twice in a row is 1 in 400. This is an acceptable risk, so I'm going to attempt to cast the spell.

Now if the probability of failing twice in a row was actually 1/100 or even 1/50, I would definitely consider another course of action.

[takkaria]

Angband uses a custom RNG, and yes, the RNG state is saved to prevent savefile scumming. Someone did an analysis years ago comparing it to the Mersenne Twister, and it had comparable levels of randomness as far as I can recall. That said, it does seem odd how often I fail a 15% spell chance several times in a row, doesn't it?

Angband's RNG is far far less random then MT. We could change it, but it always seemed to be part of the character of the game to me.

[Atarlost]

Not sure why Angband never switched to Mersenne Twister on the principle that nobody ever got fired for buying IBM.

[d_m]

Angband uses a custom RNG, and yes, the RNG state is saved to prevent savefile scumming. Someone did an analysis years ago comparing it to the Mersenne Twister, and it had comparable levels of randomness as far as I can recall. That said, it does seem odd how often I fail a 15% spell chance several times in a row, doesn't it?

If I remember, it's cycle is shorter than Mersenne Twister, but long enough that most people aren't going to notice (particularly with all the different unpredictable things we end up doing with entropy).

[Derakon]

Angband uses a custom RNG, and yes, the RNG state is saved to prevent savefile scumming. Someone did an analysis years ago comparing it to the Mersenne Twister, and it had comparable levels of randomness as far as I can recall. That said, it does seem odd how often I fail a 15% spell chance several times in a row, doesn't it?

[Chud]

Is the random number generation in Angband just the standard rand() from the C library?

A couple of things make me wonder... one from cheating, yes, it's true; I copied a save file for a character with 0 HP (note: still alive...) and poisoned... and since she had only one healing option, the actions from run to run were always the same (hit, miss, hit, breathe, etc) because my (healing) action was always the same. If the seed to rand() is stored in the save file, that makes sense.

The other thing that makes me wonder is that sometimes spell failure rates seem... oddly distributed, shall we say. Like, 45% failure fails 7 times in a row. Sure, it could happen... but it makes you go "hmmm..." :-)

http://www.random.org/analysis/dilbert.jpg