Does atari games are deterministic?

[Dong]

By deterministic, I mean, if I toke an action based on current state which is the frame presented on the screen, is the next frame deterministic?  Is there some possiblity control of the next frame, such like 70% for Frame_next, 30% for Frame_next_1? 

 

[Sknarp]

......yes? It's deterministic by default, with some clever use of memory addressing to try to make something less deterministic. I don't think that's what you're actually asking though? If you want to choose random things use the rand fuction and truncate the resulting value to whatever maximum you need.

[+Karl G]

It might help to give an example so we have a better idea of what you are asking.

[Dong]

6 hours ago, Karl G said:

It might help to give an example so we have a better idea of what you are asking.

Supposed now we in Breakout Game, we toke an action like moving the paddle right.  Then the the "game engine" presents the next frame (in which the ball is moving to next position, the paddle move right). This is deterministic, you give the "game engine" the action to take, then it present the next frame which is only determined by the last frame(or the state) and the action.  But in some games, even we know the current state and which action to take, but the next state could have several options.

 

For example,  in the Breakout game, if we have state S, and  action A to take, then the next state must be S1 based on S and A.

But some other games could be: state S  and action A, but the next state could be 70% for S1 and 30% for S1'. 

 

So my question is, are atari 2600 games like the first example or the second example?

 

Edited March 18, 2020 by Dong

[Keatah]

Basically what's being asked is how much randomness is in Atari games.

 

If you recorded all the inputs and played them back to the game, would the game have the same outcome? Would the characters move in the same patterns? Or would it diverge at some point to where the inputs were simply not appropriate.

 

[bluswimmer]

In an Atari game, assuming you perform the exact same inputs down to the frame, then you'll get the same result.

 

Most game software generally makes use of a pseudorandom number generator to introduce random events into a game. Essentially, the game starts with an initial "seed," and when a new random number is needed, the "seed" is passed through an algorithm to create a new "seed."

 

Obviously, this isn't actually random. To increase randomness, Atari games will often reroll the seed on every frame, even if a random number isn't needed on that frame. Additionally, the algorithm may take player input into account when generating a new seed.

 

In most modern games, the RNG's initial seed is usually the system's current date and time, down to the millisecond, which usually creates enough randomness to be unnoticeable. As such, the methods described above are less common there.