Answers.Body: <p>The <a href="https://en.wikipedia.org/wiki/Chess_World_Cup_2017#Participants" rel="nofollow noreferrer">participants</a> were seeded by their FIDE rating: the highest rated player (Magnus Carlsen, 2822) got #1; Wesley So, rated 2810, got #2, all the way down to Oluwafemi Balogun (2255), seed #128.</p>
  
  <p>In the first round, the player with number <em>x</em> plays against the opponent with number <em>129 - x</em>. So 1 vs. 128, 2 vs. 127, and so on.</p>
  
  <p>In the second round, assuming the stronger player (with the lower number) advances, the player with number <em>x</em> plays against the opponent with number <em>65 - x</em>. So 1 vs. 64 (this actually happened) and 9 vs. 56 (but this became 9 vs. 73 since 73 beat 56).</p>
  
  <p>The 'target sum' for the third round is 33, for the fourth round 17, and so on until the final where #1 is supposed to play against #2.</p>
  
  <p>This all is a standard <a href="https://en.wikipedia.org/wiki/Seed_(sports)" rel="nofollow noreferrer">seeding mechanism</a> used in many sports (sometimes with slight variations); actually, in most cases, only the top n% (25% is common) of the players is seeded and the rest are paired randomly. This tournament was 'completely' seeded, which is relatively rare.</p>
  
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Answers.Text: Thanks. This explains the pairings for the first round. But which bracket does each player get into?
Answers.UserDisplayName: Wais Kamal
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Answers.Text: @WaisKamal That's determined by the seeding. If you have 128 players and the brackets cover the first 4 rounds, then in round 5 you're aiming for seed 1 to play seed 8. So, if seed 1 is in bracket 1, seed 8 needs to be in bracket 2.
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Answers.Text: One also has to be clever in assigning colors. If you give all the top half the same color in round 1 you will soon run into problems.  The usual is to reverse color so the initial even numbers get black and the initial odds get white.  Some directors may flip a coin to see which color the top player starts with.
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Body: <p><a href="https://en.wikipedia.org/wiki/Chess_World_Cup_2017" rel="nofollow noreferrer">Here</a> are the pairings for the 2017 FIDE World Cup. The above pairings are for 128-player knockouts. I can't get the way the pairings were generated. I want to be able to generate pairings using the same criteria for knockouts with different numbers of players.</p>
  
  <p>Are there any FIDE published rules for single-elimination tournaments, such as the World Cup? If not, what are the criteria they use for such pairings?</p>
  
  <p><em>As it stands, there are no <a href="/questions/tagged/knockout" class="post-tag" title="show questions tagged &#39;knockout&#39;" rel="tag">knockout</a>, <a href="/questions/tagged/single-elimination" class="post-tag" title="show questions tagged &#39;single-elimination&#39;" rel="tag">single-elimination</a> or <a href="/questions/tagged/pairing" class="post-tag" title="show questions tagged &#39;pairing&#39;" rel="tag">pairing</a> tags. I couldn't find appropriate tags, so feel free to re-tag this question.</em></p>
  
Tags: <tournament>
Title: What are the pairing regulations for a single-elimination (knockout) tournament?
ThreadText: # What are the pairing regulations for a single-elimination (knockout) tournament?
  
  (Asked by: username_0 on 2019-05-24)
  
  [Here](https://en.wikipedia.org/wiki/Chess_World_Cup_2017) are the pairings for the 2017 FIDE World Cup. The above pairings are for 128-player knockouts. I can't get the way the pairings were generated. I want to be able to generate pairings using the same criteria for knockouts with different numbers of players.
  
  Are there any FIDE published rules for single-elimination tournaments, such as the World Cup? If not, what are the criteria they use for such pairings?
  
  *As it stands, there are no [knockout](/questions/tagged/knockout "show questions tagged 'knockout'"), [single-elimination](/questions/tagged/single-elimination "show questions tagged 'single-elimination'") or [pairing](/questions/tagged/pairing "show questions tagged 'pairing'") tags. I couldn't find appropriate tags, so feel free to re-tag this question.*
  
  **Tags:** tournament
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2019-05-24. Score: 4
  
  The [participants](https://en.wikipedia.org/wiki/Chess_World_Cup_2017#Participants) were seeded by their FIDE rating: the highest rated player (Magnus Carlsen, 2822) got #1; Wesley So, rated 2810, got #2, all the way down to Oluwafemi Balogun (2255), seed #128.
  
  In the first round, the player with number *x* plays against the opponent with number *129 - x*. So 1 vs. 128, 2 vs. 127, and so on.
  
  In the second round, assuming the stronger player (with the lower number) advances, the player with number *x* plays against the opponent with number *65 - x*. So 1 vs. 64 (this actually happened) and 9 vs. 56 (but this became 9 vs. 73 since 73 beat 56).
  
  The 'target sum' for the third round is 33, for the fourth round 17, and so on until the final where #1 is supposed to play against #2.
  
  This all is a standard [seeding mechanism](https://en.wikipedia.org/wiki/Seed_(sports)) used in many sports (sometimes with slight variations); actually, in most cases, only the top n% (25% is common) of the players is seeded and the rest are paired randomly. This tournament was 'completely' seeded, which is relatively rare.
  
  > **Comments:**
  > **username_0**: Thanks. This explains the pairings for the first round. But which bracket does each player get into?  
  > **username_2**: @username_0 That's determined by the seeding. If you have 128 players and the brackets cover the first 4 rounds, then in round 5 you're aiming for seed 1 to play seed 8. So, if seed 1 is in bracket 1, seed 8 needs to be in bracket 2.  
  > **username_3**: One also has to be clever in assigning colors. If you give all the top half the same color in round 1 you will soon run into problems.  The usual is to reverse color so the initial even numbers get black and the initial odds get white.  Some directors may flip a coin to see which color the top player starts with.  
  
  ---
  
  