• Log InLog In
  • Register
Liquid`
Team Liquid Liquipedia
EST 05:23
CET 11:23
KST 19:23
  • Home
  • Forum
  • Calendar
  • Streams
  • Liquipedia
  • Features
  • Store
  • EPT
  • TL+
  • StarCraft 2
  • Brood War
  • Smash
  • Heroes
  • Counter-Strike
  • Overwatch
  • Liquibet
  • Fantasy StarCraft
  • TLPD
  • StarCraft 2
  • Brood War
  • Blogs
Forum Sidebar
Events/Features
News
Featured News
RSL Season 3 - Playoffs Preview0RSL Season 3 - RO16 Groups C & D Preview0RSL Season 3 - RO16 Groups A & B Preview2TL.net Map Contest #21: Winners12Intel X Team Liquid Seoul event: Showmatches and Meet the Pros10
Community News
[BSL21] Ro.16 Group Stage (C->B->A->D)1Weekly Cups (Nov 17-23): Solar, MaxPax, Clem win2RSL Season 3: RO16 results & RO8 bracket13Weekly Cups (Nov 10-16): Reynor, Solar lead Zerg surge2[TLMC] Fall/Winter 2025 Ladder Map Rotation14
StarCraft 2
General
Weekly Cups (Nov 17-23): Solar, MaxPax, Clem win SC: Evo Complete - Ranked Ladder OPEN ALPHA Weekly Cups (Nov 10-16): Reynor, Solar lead Zerg surge RSL Season 3: RO16 results & RO8 bracket RSL Season 3 - Playoffs Preview
Tourneys
RSL Revival: Season 3 $5,000+ WardiTV 2025 Championship StarCraft Evolution League (SC Evo Biweekly) Constellation Cup - Main Event - Stellar Fest 2025 RSL Offline Finals Dates + Ticket Sales!
Strategy
Custom Maps
Map Editor closed ?
External Content
Mutation # 501 Price of Progress Mutation # 500 Fright night Mutation # 499 Chilling Adaptation Mutation # 498 Wheel of Misfortune|Cradle of Death
Brood War
General
Data analysis on 70 million replays 2v2 maps which are SC2 style with teams together? [BSL21] Ro.16 Group Stage (C->B->A->D) soO on: FanTaSy's Potential Return to StarCraft What happened to TvZ on Retro?
Tourneys
[Megathread] Daily Proleagues [BSL21] RO16 Tie Breaker - Group B - Sun 21:00 CET [BSL21] RO16 Tie Breaker - Group A - Sat 21:00 CET Small VOD Thread 2.0
Strategy
Game Theory for Starcraft How to stay on top of macro? Current Meta PvZ map balance
Other Games
General Games
Stormgate/Frost Giant Megathread Should offensive tower rushing be viable in RTS games? Nintendo Switch Thread Clair Obscur - Expedition 33 Path of Exile
Dota 2
Official 'what is Dota anymore' discussion
League of Legends
Heroes of the Storm
Simple Questions, Simple Answers Heroes of the Storm 2.0
Hearthstone
Deck construction bug Heroes of StarCraft mini-set
TL Mafia
Mafia Game Mode Feedback/Ideas
Community
General
US Politics Mega-thread Russo-Ukrainian War Thread YouTube Thread Artificial Intelligence Thread Things Aren’t Peaceful in Palestine
Fan Clubs
White-Ra Fan Club The herO Fan Club!
Media & Entertainment
[Manga] One Piece Movie Discussion! Anime Discussion Thread
Sports
2024 - 2026 Football Thread Formula 1 Discussion NBA General Discussion MLB/Baseball 2023 TeamLiquid Health and Fitness Initiative For 2023
World Cup 2022
Tech Support
Computer Build, Upgrade & Buying Resource Thread
TL Community
The Automated Ban List
Blogs
The Health Impact of Joining…
TrAiDoS
Dyadica Evangelium — Chapt…
Hildegard
Saturation point
Uldridge
DnB/metal remix FFO Mick Go…
ImbaTosS
Customize Sidebar...

Website Feedback

Closed Threads



Active: 2065 users

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.
Administrator
Please log in or register to reply.
Live Events Refresh
Next event in 1h 37m
[ Submit Event ]
Live Streams
Refresh
StarCraft 2
SortOf 188
StarCraft: Brood War
Calm 4108
Sea 1942
Larva 467
BeSt 451
Killer 336
Stork 283
PianO 270
Hyun 233
ZerO 221
firebathero 179
[ Show more ]
Pusan 151
Leta 101
Light 96
Rush 87
soO 83
ToSsGirL 78
sorry 48
Sacsri 37
Backho 28
Sharp 25
Free 23
ajuk12(nOOB) 22
Terrorterran 11
Bale 10
Dota 2
XcaliburYe6
League of Legends
JimRising 532
Trikslyr27
Counter-Strike
olofmeister1408
shoxiejesuss582
oskar67
Other Games
summit1g9425
ceh9600
Fuzer 217
crisheroes197
Mew2King136
QueenE100
NeuroSwarm61
ZerO(Twitch)13
MindelVK13
Pyrionflax11
Organizations
Other Games
gamesdonequick605
Dota 2
PGL Dota 2 - Main Stream460
StarCraft 2
Blizzard YouTube
StarCraft: Brood War
BSLTrovo
sctven
[ Show 17 non-featured ]
StarCraft 2
• Berry_CruncH224
• LUISG 28
• Adnapsc2 10
• Kozan
• AfreecaTV YouTube
• intothetv
• sooper7s
• Migwel
• IndyKCrew
• LaughNgamezSOOP
StarCraft: Brood War
• iopq 9
• STPLYoutube
• ZZZeroYoutube
• BSLYoutube
Dota 2
• WagamamaTV159
League of Legends
• Jankos1246
• HappyZerGling130
Upcoming Events
Wardi Open
1h 37m
PiGosaur Cup
14h 37m
Replay Cast
22h 37m
Wardi Open
1d 1h
OSC
1d 2h
Tenacious Turtle Tussle
1d 13h
The PondCast
1d 23h
Replay Cast
2 days
OSC
3 days
LAN Event
3 days
[ Show More ]
Replay Cast
3 days
Replay Cast
3 days
WardiTV Korean Royale
4 days
Sparkling Tuna Cup
4 days
WardiTV Korean Royale
5 days
Replay Cast
5 days
Wardi Open
6 days
Replay Cast
6 days
Liquipedia Results

Completed

SOOP Univ League 2025
RSL Revival: Season 3
Eternal Conflict S1

Ongoing

C-Race Season 1
IPSL Winter 2025-26
KCM Race Survival 2025 Season 4
YSL S2
BSL Season 21
CSCL: Masked Kings S3
SLON Tour Season 2
META Madness #9
SL Budapest Major 2025
BLAST Rivals Fall 2025
IEM Chengdu 2025
PGL Masters Bucharest 2025
Thunderpick World Champ.
CS Asia Championships 2025
ESL Pro League S22
StarSeries Fall 2025
FISSURE Playground #2

Upcoming

BSL 21 Non-Korean Championship
Acropolis #4
IPSL Spring 2026
HSC XXVIII
RSL Offline Finals
WardiTV 2025
IEM Kraków 2026
BLAST Bounty Winter 2026
BLAST Bounty Winter 2026: Closed Qualifier
eXTREMESLAND 2025
ESL Impact League Season 8
TLPD

1. ByuN
2. TY
3. Dark
4. Solar
5. Stats
6. Nerchio
7. sOs
8. soO
9. INnoVation
10. Elazer
1. Rain
2. Flash
3. EffOrt
4. Last
5. Bisu
6. Soulkey
7. Mini
8. Sharp
Sidebar Settings...

Advertising | Privacy Policy | Terms Of Use | Contact Us

Original banner artwork: Jim Warren
The contents of this webpage are copyright © 2025 TLnet. All Rights Reserved.