• Log InLog In
  • Register
Liquid`
Team Liquid Liquipedia
EST 05:27
CET 11:27
KST 19:27
  • 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
SC2 All-Star Invitational: Tournament Preview5RSL Revival - 2025 Season Finals Preview8RSL Season 3 - Playoffs Preview0RSL Season 3 - RO16 Groups C & D Preview0RSL Season 3 - RO16 Groups A & B Preview2
Community News
BSL Season 2025 - Full Overview and Conclusion6Weekly Cups (Jan 5-11): Clem wins big offline, Trigger upsets4$21,000 Rongyi Cup Season 3 announced (Jan 22-Feb 7)16Weekly Cups (Dec 29-Jan 4): Protoss rolls, 2v2 returns7[BSL21] Non-Korean Championship - Starts Jan 105
StarCraft 2
General
Stellar Fest "01" Jersey Charity Auction SC2 All-Star Invitational: Tournament Preview Weekly Cups (Jan 5-11): Clem wins big offline, Trigger upsets When will we find out if there are more tournament SC2 Spotted on the EWC 2026 list?
Tourneys
SC2 All-Star Invitational: Jan 17-18 Sparkling Tuna Cup - Weekly Open Tournament SC2 AI Tournament 2026 $21,000 Rongyi Cup Season 3 announced (Jan 22-Feb 7) OSC Season 13 World Championship
Strategy
Simple Questions Simple Answers
Custom Maps
Map Editor closed ?
External Content
Mutation # 508 Violent Night Mutation # 507 Well Trained Mutation # 506 Warp Zone Mutation # 505 Rise From Ashes
Brood War
General
BSL Season 2025 - Full Overview and Conclusion Video Footage from 2005: The Birth of G2 in Spain [ASL21] Potential Map Candidates Fantasy's Q&A video BGH Auto Balance -> http://bghmmr.eu/
Tourneys
[BSL21] Grand Finals - Sunday 21:00 CET [Megathread] Daily Proleagues [BSL21] Non-Korean Championship - Starts Jan 10 Small VOD Thread 2.0
Strategy
Soma's 9 hatch build from ASL Game 2 Simple Questions, Simple Answers Game Theory for Starcraft Current Meta
Other Games
General Games
Stormgate/Frost Giant Megathread Beyond All Reason Awesome Games Done Quick 2026! Nintendo Switch Thread Mechabellum
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
Vanilla Mini Mafia Mafia Game Mode Feedback/Ideas
Community
General
US Politics Mega-thread Things Aren’t Peaceful in Palestine Russo-Ukrainian War Thread Canadian Politics Mega-thread European Politico-economics QA Mega-thread
Fan Clubs
The IdrA Fan Club
Media & Entertainment
Anime Discussion Thread [Manga] One Piece
Sports
2024 - 2026 Football Thread
World Cup 2022
Tech Support
Computer Build, Upgrade & Buying Resource Thread
TL Community
The Automated Ban List
Blogs
My 2025 Magic: The Gathering…
DARKING
Physical Exercise (HIIT) Bef…
TrAiDoS
Life Update and thoughts.
FuDDx
How do archons sleep?
8882
James Bond movies ranking - pa…
Topin
Customize Sidebar...

Website Feedback

Closed Threads



Active: 1602 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
All-Star Invitational
03:00
Day 2
WardiTV1263
PiGStarcraft610
IndyStarCraft 255
EnkiAlexander 62
LiquipediaDiscussion
Sparkling Tuna Cup
10:00
Weekly #117
CranKy Ducklings94
LiquipediaDiscussion
[ Submit Event ]
Live Streams
Refresh
StarCraft 2
PiGStarcraft610
IndyStarCraft 255
MindelVK 108
StarCraft: Brood War
Rain 4814
firebathero 1116
Shuttle 706
Hyuk 659
Larva 576
BeSt 478
Stork 355
actioN 320
Hm[arnc] 230
Soma 212
[ Show more ]
Hyun 152
Mini 140
Light 127
sorry 124
Rush 110
Leta 100
Sharp 89
Last 88
Shine 63
ToSsGirL 51
Free 38
yabsab 32
HiyA 28
NotJumperer 24
zelot 20
Sacsri 18
ajuk12(nOOB) 16
Noble 13
Terrorterran 9
Dota 2
XcaliburYe292
League of Legends
JimRising 564
C9.Mang0458
Counter-Strike
allub415
Other Games
Fuzer 225
Sick212
crisheroes159
Mew2King52
EmSc Tv 8
Organizations
Other Games
gamesdonequick2263
EmSc Tv 8
StarCraft 2
EmSc2Tv 8
Blizzard YouTube
StarCraft: Brood War
BSLTrovo
sctven
[ Show 17 non-featured ]
StarCraft 2
• Berry_CruncH101
• naamasc228
• Kozan
• Migwel
• AfreecaTV YouTube
• sooper7s
• intothetv
• IndyKCrew
• LaughNgamezSOOP
• Laughngamez YouTube
StarCraft: Brood War
• blackmanpl 24
• STPLYoutube
• ZZZeroYoutube
• BSLYoutube
Dota 2
• lizZardDota289
League of Legends
• Jankos2191
• Stunt512
Upcoming Events
OSC
1h 33m
Shameless vs NightMare
YoungYakov vs MaNa
Nicoract vs Jumy
Gerald vs TBD
Creator vs TBD
BSL 21
9h 33m
Bonyth vs Sziky
Mihu vs QiaoGege
Sziky vs XuanXuan
eOnzErG vs QiaoGege
Mihu vs DuGu
Dewalt vs Bonyth
IPSL
9h 33m
Dewalt vs Sziky
Replay Cast
22h 33m
Wardi Open
1d 1h
Monday Night Weeklies
1d 6h
The PondCast
2 days
Big Brain Bouts
5 days
Serral vs TBD
BSL 21
6 days
Liquipedia Results

Completed

Escore Tournament S1: W4
Big Gabe Cup #3
NA Kuram Kup

Ongoing

C-Race Season 1
IPSL Winter 2025-26
BSL 21 Non-Korean Championship
CSL 2025 WINTER (S19)
KCM Race Survival 2026 Season 1
OSC Championship Season 13
SC2 All-Star Inv. 2025
Underdog Cup #3
BLAST Bounty Winter Qual
eXTREMESLAND 2025
SL Budapest Major 2025
ESL Impact League Season 8
BLAST Rivals Fall 2025
IEM Chengdu 2025

Upcoming

Escore Tournament S1: W5
Acropolis #4
IPSL Spring 2026
Bellum Gens Elite Stara Zagora 2026
HSC XXVIII
Rongyi Cup S3
Nations Cup 2026
Stake Ranked Episode 1
BLAST Open Spring 2026
ESL Pro League Season 23
ESL Pro League Season 23
PGL Cluj-Napoca 2026
IEM Kraków 2026
BLAST Bounty Winter 2026
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 © 2026 TLnet. All Rights Reserved.