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Probability of Mirror Matchups in rvr

Forum Index > BW General
Post a Reply
Qizix
Profile Joined February 2009
3 Posts
March 15 2009 23:14 GMT
#1
I'm sure somebody has posted this, but I haven't found anything on this.

I play fastest, where most 1v1's are random vs. random. I was wondering what the chances are that the game will become a mirror matchups. I have to say that I play almost no mirror matchups, but when I think about the chances, it seems as though the probability for mirror matchups is higher than the amount I receive. Why is this?
Survival of the Fittest
Jayme
Profile Blog Joined February 2009
United States5866 Posts
Last Edited: 2009-03-15 23:20:02
March 15 2009 23:18 GMT
#2
1/3 x 1/3 = 1 in every 9 games.

It's simply random.

Edit: I'm a moron.

Chances are 1/3. Lol lol
Python is garbage, number 1 advocate of getting rid of it.
]343[
Profile Blog Joined May 2008
United States10328 Posts
Last Edited: 2009-03-15 23:26:28
March 15 2009 23:18 GMT
#3
try 1/3?

pick any race for 1st (probability 1), then probability of 2nd being same is 1/3.

or

3 mirror matchups out of 3*3 matchups = 1/3?
Writer
Senix
Profile Joined October 2004
Germany149 Posts
March 15 2009 23:19 GMT
#4
You have a total of 9 (3*3)possible matchups in rvr and 3 (tvt zvz pvp) of those are mirrors. Therefore the probability of a mirror matchup in rvr is 3/9 =1/3. On average every 3rd game you play will be a mirror.
Tracil
Profile Blog Joined September 2005
Australia505 Posts
Last Edited: 2009-03-15 23:20:36
March 15 2009 23:20 GMT
#5
Shooting
Zherak
Profile Blog Joined November 2007
Norway256 Posts
Last Edited: 2009-03-15 23:22:12
March 15 2009 23:21 GMT
#6
There was a huge thread about this a long time ago.

The only thing I can say completely confidently is that it is not random. That is, you do not get mirrors every third game as one would expect. I seem to remember the odds coming out as 1 out of 9. Not as in 1/9 for TvT, but 1/9 for TvT, PvP and ZvZ all added together.

If four players all go random, you will get 2/1/1 distribution nearly every single time. I ran a series of test because I considered it ridiculous for random to not actually be random, but, well, it isn't. Just like miss chance isn't 30% I guess.
The bowsprit got mixed with the rudder sometimes...
Qizix
Profile Joined February 2009
3 Posts
Last Edited: 2009-03-15 23:24:54
March 15 2009 23:24 GMT
#7
I know all of that. I'm not that stupid. The thing is, that doesn't happen. For example, if you go to vile Gaming or just try seeing how many times you get mirror matchups, I find that I don't get them one out of every nine games.

For example, on vile gaming, there have been 2,791 matches played. Out of those 186 games have been mirror matches. That multiplied by nine equals 1674 matches. Why is it that the numbers aren't closer together?

Edit: Didn't see the previous post, but that is what I was thinking of.
Survival of the Fittest
]343[
Profile Blog Joined May 2008
United States10328 Posts
March 15 2009 23:25 GMT
#8
On March 16 2009 08:21 Zherak wrote:
There was a huge thread about this a long time ago.

The only thing I can say completely confidently is that it is not random. That is, you do not get mirrors every third game as one would expect. I seem to remember the odds coming out as 1 out of 9. Not as in 1/9 for TvT, but 1/9 for TvT, PvP and ZvZ all added together.

If four players all go random, you will get 2/1/1 distribution nearly every single time. I ran a series of test because I considered it ridiculous for random to not actually be random, but, well, it isn't. Just like miss chance isn't 30% I guess.


hmm I wouldn't be surprised if this were true

however 2/1/1 has... multinomial(4, (2, 1, 1)) = 4!/2! = 12 ways [assuming the 2 race is fixed, so x3], and 1/3^4 = 81 probability/thing, so... the probability it's 2/1/1 is 4/9 (which is pretty high) :O
Writer
Faronel
Profile Blog Joined July 2008
United States658 Posts
March 15 2009 23:26 GMT
#9
Zherak that idea is wrong in this case, since we're looking for mirror match ups. It's still 1/3 when at the end because the 1st choice can be anything from the 3/3/2 distribution and the 2nd choice is also from the 3/3/2 distribution, being that the zerg (2) 's low probability is offset by the protoss and terran probabilities, it will be 1/3.

I guess it makes sense that it's not random since blizzard probably only but 1 byte of info for the random race generator: i.e. 1 byte = 8 choices --> pseudorandom
http://en.wikipedia.org/wiki/Pseudorandom_number_generator
C'est la vie...
]343[
Profile Blog Joined May 2008
United States10328 Posts
March 15 2009 23:28 GMT
#10
On March 16 2009 08:26 Faronel wrote:
Zherak that idea is wrong in this case, since we're looking for mirror match ups. It's still 1/3 when at the end because the 1st choice can be anything from the 3/3/2 distribution and the 2nd choice is also from the 3/3/2 distribution, being that the zerg (2) 's low probability is offset by the protoss and terran probabilities, it will be 1/3.

I guess it makes sense that it's not random since blizzard probably only but 1 byte of info for the random race generator: i.e. 1 byte = 8 choices --> pseudorandom
http://en.wikipedia.org/wiki/Pseudorandom_number_generator


wait so you're saying chance for zerg is only 1/4? interesting...
Writer
Patriot.dlk
Profile Blog Joined October 2004
Sweden5462 Posts
Last Edited: 2009-03-15 23:29:06
March 15 2009 23:28 GMT
#11
This huge post has it all covered, written by blizzard guy:

[image loading]
Kaolla
Profile Joined January 2003
China2999 Posts
March 15 2009 23:36 GMT
#12
On March 16 2009 08:28 Patriot.dlk wrote:
This huge post has it all covered, written by blizzard guy:

[image loading]


2nd time ive seen that today, supposed to be funny? oo;
its me
Avidkeystamper
Profile Blog Joined June 2008
United States8556 Posts
March 15 2009 23:44 GMT
#13
Hot_Bid trolling like the troll he is.
Jaedong
Zherak
Profile Blog Joined November 2007
Norway256 Posts
March 15 2009 23:48 GMT
#14
Okay, all nonsense aside:

http://www.teamliquid.net/forum/viewmessage.php?topic_id=37059&currentpage=2

That ought to cover it.
The bowsprit got mixed with the rudder sometimes...
MasterOfChaos
Profile Blog Joined April 2007
Germany2896 Posts
March 15 2009 23:49 GMT
#15
There is only possible explanation for the deviation from 1/3: Blizzard has invented the improbability drive.
LiquipediaOne eye to kill. Two eyes to live.
Zherak
Profile Blog Joined November 2007
Norway256 Posts
March 15 2009 23:52 GMT
#16
That said, I would love somebody to post the actual details on how this thing works. Even the thread I linked is rather, well, unclear, on how it really works.
The bowsprit got mixed with the rudder sometimes...
Nytefish
Profile Blog Joined December 2007
United Kingdom4282 Posts
March 16 2009 00:00 GMT
#17
I'm quite curious about this "random" algorithm too.
No I'm never serious.
WhuazGoodJaggah
Profile Blog Joined January 2009
Lesotho777 Posts
March 16 2009 00:11 GMT
#18
this thread explains it good. dt says in th elast post that the chance of mirror is 1/8
http://www.bwhacks.com/forums/starcraft-hacking-related/30728-random-race-test.html
small dicks have great firepower
SonuvBob
Profile Blog Joined October 2006
Aiur21550 Posts
March 16 2009 00:27 GMT
#19
On March 16 2009 08:49 MasterOfChaos wrote:
There is only possible explanation for the deviation from 1/3: Blizzard has invented the improbability drive.

Even with infinite improbability Blizzard still can't release a game on time.
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