How Random is 'Random'?

[Choose Goose]

Just curious if anyone knows how the random options in training mode are done (from a technical standpoint).

Default rand()? I Ching?? Mike Z throwing darts???

 

[DukeMagus]

Random calculations converted into the actual result

 

[Mike_Z]

_seed = _seed * 1103515245 + 12345; // want to keep ALL this information
unsigned toReturn = (unsigned int)(_seed/65536) % 32768; // want to return a controlled number

srand(time) at some point to start with. I don't remember why any of it.

[edit]Not really srand, but y'know start-the-seed-with-it, because it's our own rng and seed. There are a bunch of different RNGs instantiated for different things.

 

[Pikmario]

(unsigned int)(_seed/65536) % 32768;

There's nothing I don't like about this operation.

 

[Choose Goose]

_seed = _seed * 1103515245 + 12345; // want to keep ALL this information
unsigned toReturn = (unsigned int)(_seed/65536) % 32768; // want to return a controlled number

srand(time) at some point to start with. I don't remember why any of it.

So after googling that first line, you get http://en.wikipedia.org/wiki/Linear_congruential_generator with an entry listing common parameters. So that matches that. Then 65536 is the largest value a unsigned short can handle, 32768 is the largest for a signed short.

You go from 16-30 bits to 16 then modulo to end up with a number between 0 and 32767. Can I see an example of what would use this value~

tl;dr you didn't know what to do and googled it lel

 

[Mike_Z]

You know it. Random enough for someone else is random enough for me! We only use ranges like 0-1000 ever anyway.

 

[Choose Goose]

Someone write an article and title it "Google Supported Development of Skullgirls".

Thanks again Mike!