SwissTennis Seeding Placement Algorithm — Single Elimination¶

Author: Rafael (Domain Expert)
Date: 2026-04-12
Scope: R-category (club-level) single elimination brackets
Caveat: Based on SwissTennis Turnierreglement as of early 2025. Verify against latest published regulations on swisstennis.ch.

1. Does SwissTennis differ from ITF?¶

Short answer: The placement positions are identical to ITF. The differences are procedural/contextual.

SwissTennis explicitly adopts the ITF seeding placement template. The bracket positions for seeds are the same as used worldwide. The differences are:

Seeding basis: Swiss classification (Klassierung, R1-R9 scale) — not ITF/ATP/WTA rankings
Fewer seeds recommended: draw_size / 4 (not draw_size / 2)
Deterministic placement accepted at R-category level (no draw ceremony needed for seeds 3-4, 5-8 group assignment)
Wildcard seeding: Permitted but discouraged by convention

2. Regulation References¶

SwissTennis Turnierreglement — sections on "Setzliste" and "Tableau"
SwissTennis Wettspielordnung (WSO) — competition regulations
ITF Rules of Tennis, Appendix on Tournament Draws (adopted by reference for anything not overridden)

3. Number of Seeds by Draw Size¶

Draw Size	Min Seeds	Max Seeds	Recommended
4	2	2	2
8	2	4	2-4
16	2	8	4
32	4	16	8
64	8	32	16

Formula: recommended seeds = draw_size / 4 (rounded to nearest power of 2).

4. Qualifiers, Wildcards, Lucky Losers¶

Wildcards (WC): May be seeded if classification warrants it, but by convention are NOT seeded. Placed in unseeded slots.
Qualifiers (Q): NEVER seeded in main draw. Placed in designated qualifier slots (adjacent to seeds).
Lucky Losers (LL): NEVER seeded. Replace withdrawn players in their exact draw position. If a seeded player withdraws before the draw, the seed is reassigned to the next eligible player (not the LL). If withdrawal is after the draw, LL takes the position but loses the "seeded" label.
Byes: Adjacent to seeded players. Seed 1 gets first bye, seed 2 gets second, etc.

5. Placement Algorithm¶

General Principle¶

For a draw of size N (power of 2), seeds are separated maximally:

Seed 1 and 2 are in opposite halves (positions 1 and N)
Seeds 3-4 are at the opposite quarter boundaries
Seeds 5-8 are at the opposite eighth boundaries
Pattern continues recursively for seeds 9-16, 17-32, etc.

Deterministic Placement (Recommended for Implementation)¶

For R-category tournaments, use deterministic assignment (no random draw within seed groups):

Seed 1 -> Line 1 (top)
Seed 2 -> Line N (bottom)
Seed 3 -> Bottom of top half (line N/2)
Seed 4 -> Top of bottom half (line N/2 + 1)
Seed 5 -> Bottom of quarter 1 (line N/4)
Seed 6 -> Top of quarter 4 (line 3N/4 + 1)
Seed 7 -> Top of quarter 2 (line N/4 + 1)
Seed 8 -> Bottom of quarter 3 (line 3N/4)

For seeds 9-16, the same separation principle applies at the sixteenth level.

Draw of 8 — Position Map¶

Line 1: Seed 1
Line 2: (unseeded)
Line 3: (unseeded)
Line 4: Seed 3
Line 5: Seed 4
Line 6: (unseeded)
Line 7: (unseeded)
Line 8: Seed 2

With 4 seeds:

Line 1: Seed 1
Line 2: (unseeded)
Line 3: Seed 5/Q/unseeded
Line 4: Seed 3
Line 5: Seed 4
Line 6: Seed 6/Q/unseeded
Line 7: (unseeded)
Line 8: Seed 2

Draw of 16 — Position Map¶

Line 1:  Seed 1
Line 2:  (unseeded)
Line 3:  (unseeded)
Line 4:  Seed 5
Line 5:  Seed 3
Line 6:  (unseeded)
Line 7:  (unseeded)
Line 8:  Seed 7
Line 9:  Seed 6
Line 10: (unseeded)
Line 11: (unseeded)
Line 12: Seed 4
Line 13: Seed 8
Line 14: (unseeded)
Line 15: (unseeded)
Line 16: Seed 2

Draw of 32 — Position Map¶

Line 1:  Seed 1
Line 2:  (unseeded)
Line 3:  (unseeded)
Line 4:  Seed 9
Line 5:  (unseeded)
Line 6:  (unseeded)
Line 7:  (unseeded)
Line 8:  Seed 5
Line 9:  Seed 3
Line 10: (unseeded)
Line 11: (unseeded)
Line 12: Seed 11
Line 13: (unseeded)
Line 14: (unseeded)
Line 15: (unseeded)
Line 16: Seed 7
Line 17: Seed 6
Line 18: (unseeded)
Line 19: (unseeded)
Line 20: Seed 12
Line 21: (unseeded)
Line 22: (unseeded)
Line 23: (unseeded)
Line 24: Seed 4
Line 25: Seed 8
Line 26: (unseeded)
Line 27: (unseeded)
Line 28: Seed 10
Line 29: (unseeded)
Line 30: (unseeded)
Line 31: (unseeded)
Line 32: Seed 2

Programmatic Formula¶

To compute seeded positions for any draw size N:

function getSeedPositions(drawSize: number): Map<number, number> {
  const positions = new Map<number, number>();

  // Seed 1 always at line 1, Seed 2 always at line N
  positions.set(1, 1);
  positions.set(2, drawSize);

  // For each subsequent seed group (power of 2):
  // Group k contains seeds from 2^(k-1)+1 to 2^k
  // They are placed at the boundaries of 2^k sections

  // Seeds 3-4: quarter boundaries
  positions.set(3, drawSize / 2);
  positions.set(4, drawSize / 2 + 1);

  // Seeds 5-8: eighth boundaries
  if (drawSize >= 16) {
    positions.set(5, drawSize / 4);
    positions.set(6, 3 * drawSize / 4 + 1);
    positions.set(7, drawSize / 4 + 1);
    positions.set(8, 3 * drawSize / 4);
  }

  // Seeds 9-16: sixteenth boundaries
  // Pattern: each seed in the group fills the midpoint of remaining sections
  // ensuring maximum separation from all higher seeds

  return positions;
}

Note: The exact positions for seeds 9-16 and beyond follow a recursive halving pattern. The implementation should use the standard "binary tree" placement algorithm where each new seed group fills the midpoints of the sections defined by all previously placed seeds.

6. Non-Power-of-2 Draw Sizes¶

When the number of entries is not a power of 2:

Round up to the next power of 2 to determine bracket size
Place byes in the bracket (number of byes = bracket_size - num_players)
Byes are placed adjacent to seeds: Seed 1 gets first bye, Seed 2 gets second, etc.
Remaining byes go to seeds 3, 4, 5... in order
If there are more byes than seeds, remaining byes are distributed evenly (alternating top/bottom)

7. Implementation Recommendations¶

Use deterministic placement — no random draw needed for R-category
Default to draw_size/4 seeds — allow Tournament Director to override
Store the seed-to-position mapping in a lookup table for draw sizes 4, 8, 16, 32, 64
Validate: no two seeds in the same quarter (for seeds 1-4) or same eighth (for seeds 1-8)
Support manual override: Tournament Director may adjust seeding order based on recent form (Turnierreglement allows discretion)