Artifacts and Banishment

[MattB]

I hang out in a forum dedicated to the creation of "tool-assisted speedruns" of videogames, where the community members strive to generate the sequences of inputs that will complete a game as quickly as possible, without the limitations of how precisely and quickly an actual human can generate those inputs. They mostly focus on console games which start up with a known state; by running the game within an emulator they can examine the state of memory, including of the RNG, and thereby arrange things such that the random numbers they need naturally occur exactly when they are needed. For example, in a fight the opponent always misses and the player always gets critical hits. This isn't done by "cheating" (by forcing the RNG into a specific state), but rather by knowing the process by which the RNG generates numbers and making certain that the inputs to the RNG and the timing used to "consume" its numbers result in the desired outcomes.

Well, after half an hour on the site I am still utterly mystified. They're not nice and friendly like us, though...

[Nick]

I hang out in a forum dedicated to the creation of "tool-assisted speedruns" of videogames, where the community members strive to generate the sequences of inputs that will complete a game as quickly as possible, without the limitations of how precisely and quickly an actual human can generate those inputs. They mostly focus on console games which start up with a known state; by running the game within an emulator they can examine the state of memory, including of the RNG, and thereby arrange things such that the random numbers they need naturally occur exactly when they are needed. For example, in a fight the opponent always misses and the player always gets critical hits. This isn't done by "cheating" (by forcing the RNG into a specific state), but rather by knowing the process by which the RNG generates numbers and making certain that the inputs to the RNG and the timing used to "consume" its numbers result in the desired outcomes.

There are some pretty awesome "hacks" of the Pokemon games (particularly Diamond, Pearl and Platinum) based on analysing the RNG to get it into a particular state - without tool assistance.

[MattB]

Couldn't you take, say, the 3rd and 4th digit of the exact number of milliseconds since the last user imput, say 4 and 7, then take, in this instance, the 4th and 7th digit of the total physical memory usage of the computer at that time (in Kb). That would surely be as random as brownian motion?

Alternatively, all Angband players should all be able to remotely access ERNIE!

P.S. my favourite bit of that wikipedia article is "the draw is only valid if it is statistically random". What does that mean??!

[Derakon]

WOW!
Does it really work like that?

Yes. Strictly speaking the RNG is actually a PRNG -- that is, a "Pseudo-Random Number Generator"; not actually random. It generates results that look random to a human, but are actually entirely deterministic. And this is true for almost all programs in use. Computers do not innately have any source of randomness; all of their processes are deterministic. You must provide some outside input for there to be something "truly random". Some examples of this:

* Adjust the RNG based on the exact time at which the program is launched (for computers that have an externally-set clock). But the RNG is deterministic from here on.
* Start from a fixed state, but adjust the RNG very quickly (e.g. 60x/second) while waiting at the starting screen; it is unlikely that the user will wait exactly the same time before starting the program every time. But the RNG is still entirely deterministic.
* Adjust the RNG based on the timings and values of the user's inputs. Still deterministic -- if the user provides the same inputs at the same times they will get the same results. But hard to manipulate.
* Connect a module to the computer that provides randomness by measuring e.g. the movement of particles with a laser (Brownian motion). This approach is of course very rare as it requires special hardware, but can be useful for highly-secure systems that need to be unpredictable, because it actually is random.

I hang out in a forum dedicated to the creation of "tool-assisted speedruns" of videogames, where the community members strive to generate the sequences of inputs that will complete a game as quickly as possible, without the limitations of how precisely and quickly an actual human can generate those inputs. They mostly focus on console games which start up with a known state; by running the game within an emulator they can examine the state of memory, including of the RNG, and thereby arrange things such that the random numbers they need naturally occur exactly when they are needed. For example, in a fight the opponent always misses and the player always gets critical hits. This isn't done by "cheating" (by forcing the RNG into a specific state), but rather by knowing the process by which the RNG generates numbers and making certain that the inputs to the RNG and the timing used to "consume" its numbers result in the desired outcomes.

[MattB]

You can see this in a really striking way if you have a version which runs the borg - because the borg is also deterministic. So given the exact same starting character, the borg will play the exact same game every time you run it.

Well, all I can say is thank God for Hoarmurath's Uncertainty Principle!

[Nick]

I'm not really able to put into words exactly why this unsettles me so much.

You can see this in a really striking way if you have a version which runs the borg - because the borg is also deterministic. So given the exact same starting character, the borg will play the exact same game every time you run it.

[MattB]

If you always do the same actions before heading into the dungeon, then the RNG will be in the same state and will generate the same dungeon and monsters with the same items.

WOW!
Does it really work like that?
I feel a major breakdown in self-determinism that gives me a deep seated unease that never really struck me in the real world (even though it is at least as true in real life as it is in Angband).
I'm not really able to put into words exactly why this unsettles me so much.
Given identical circumstances, every human reaction would be the same (for a given particular human) and thus it would be possible from dungeon generation of dlvl zero to accurately predict what level the character would die on!
Spooky.

And, on a more technical level, I usually take the competition rules at their word, and take advantage of the 'intial shopping trip' rule before making that my recurrent savefile. Given that I always end that shopping trip on the down stair, the exact scenario you describe above would occur every time.

Thanks for the particularly perceptive answer.

[Derakon]

I seem to recall that, when playing competitions, the dlvl1 monsters always drop the same things. Which is odd, as you start at dlvl zero. Or have I imagined this? (Quite possible)

If you always do the same actions before heading into the dungeon, then the RNG will be in the same state and will generate the same dungeon and monsters with the same items.

[MattB]

I thought that monster drops are only generated once a monster is killed. So in that sense you can't banish a monster carrying an artifact, the game will only start rolling dice to see what the monster carried after you killed it.

I seem to recall that, when playing competitions, the dlvl1 monsters always drop the same things. Which is odd, as you start at dlvl zero. Or have I imagined this? (Quite possible)

[PowerWyrm]

- dlvl 60 is not that deep, if you get a huge vault with a ton of junk the feeling will be max
- feeling includes stuff that is squelched -- for example Wrath of God if you're not playing a cleric and you squelched all priest books

[Timo Pietilä]

I thought that monster drops are only generated once a monster is killed.

That used to be the case, but now every monster gets its drop/inventory created when monster is created. There was some sensible reason for this change, but I can't remember what it was.

[quarague]

I thought that monster drops are only generated once a monster is killed. So in that sense you can't banish a monster carrying an artifact, the game will only start rolling dice to see what the monster carried after you killed it.

[Timo Pietilä]

First, can monsters carry artifacts? I thought they could not, but I could be wrong...

I was in a vault which I would have expected to have a few artifacts, banished a bunch (almost all) of the monsters, and was left with 1-2 early-game artifacts at a dlvl depth of 60-65. It just seemed odd to me, although it could just be bad luck, I believe the "feeling" was 9-9, which made me think there should be something more worthwhile there, but no PDSM, Balance, etc either...

9-9 is high, very high. Dungeon only spellbooks, speed rings and all DSM count.

It is possible that there were some very high level items that got picked up and/or trampled over by elementals/Xorn/Xaren.

[Timo Pietilä]

If you have not learned the name of an artifact, then the artifact cannot be lost (when playing in preserve mode).

Also even with preserve off artifacts in monster inventory don't get lost.

[Nick]

I've always wondered whether the treasure feeling included the objects spawned in monster inventory as well as on the floor, or just the floor only. Anyone have a definitive answer?

Floor only.