Tournament blocks

This article is meant as a repository for tournament and competitive blocks used for seating arragements. The content is mainly present in tabular form: reading it for the sake of reading is not recommended.

Ideal blocks

Ideal blocks require the organizer to plan according to the situation hey are planning for. Block sizes of 4 and of 5 change the dynamic completely.

Tournament

Tournaments often require a single hanchan between 4 players and then a shuffling of new opponents, aiming to complete a maximum or a set number of hanchan with minimal or no repeats between players.

League play

Leagues may require being able to shift between blocks of 4 and 5 players who end up playing 4 hanchan among each other per session.

Block repository

Tournament blocks

Simplest solution: Dutch cycles

Dutch cycles (also called ____) serve a purpose of fairly distributing players across a set number of games, all while reducing/preventing repeats between pairs of players. This system works best when prime factors are in play, but breaks down when composite factors are used. Large player bases can mitigate some issues.

The obvious flaw with this solution is that players are segregated into blocks. The method is fair as long as players draw from one pool with all entries mixed AND that the draw occurs fairly, in the presence of all players, or failing that, that the location and time of draw be published beforehand with a fair chance for all to attend. Both NMB tournaments (2011 in Utrecht) and the 2014 WRC used this method, however they both had flaws in their implementation.

The general formula is that table t consists of players [t, t + n/4, t + 2n/4, t + 3n/4] in hanchan 0 {mathematically speaking so the formula works}, and for future hanchan h, tables consist of [t, ((t + 1*h) % n/4) + n/4, ((t + 2*h) % n/4) + 2n/4, ((t + 3*h) % n/4) + 3n/4]. Its usefulness can be demonstrated as soon as there are 44 or more participants, and preferably not a multiple of 3. Heavily composite numbers of players will lead to collisions when tables = h * factor. The 2014 WRC had 120 players over 30 tables: as 120 (as well as 30) is divisible by 3, it would lead to a collision when h = 10, making the 11th hanchan place naively two players who met before across all 30 tables.

Notes: Mathpuzzle.com has a few non-Dutch solutions for the "Social Golfer Problem". -- As does the web archive, from Warwick Harvey

Blocks of 4

Players	Block	Of	Raw data
16	1	5	ABCD EFGH IJKL MNOP
16	2	5	AEIM BFJN CGKO DHLP
16	3	5	AFKP BELO CHIN DGJM
16	4	5	AGLN BHKM CEJP DFIO
16	5	5	AHJO BGIP CFLM DEKN.
20	1	5	ABCD EFGH IJKL MNOP QRST
20	2	5	AEIM BFJQ CGNR DKOS HLPT
20	3	5	AFOT BELR CIPS DGJM HKNQ
20	4	5	AJPR BHMS CEKT DFIN GLOQ
20	5	5	ALNS BGIT CHJO DEPQ FKMR.
24	1	7	ABKU IJSE QRCM DGFX HLNO PTVW
24	2	7	ACLV IKTF QSDN EHGR BMOP JUWX
24	3	7	ADMW ILUG QTEO FBHS CJNP KRVX
24	4	7	AENX IMVH QUFP GCBT DJKO LRSW
24	5	7	AFOR INWB QVGJ HDCU EKLP MSTX
24	6	7	AEPS IOXC QWHK BEDV FJLM NRTU
24	7	7	AHJT IPRD QXBL CFEW GKMN OSUV.
28	1	9	ABCD EFGH IJKL MNab cdef ghij klmn
28	1	9	AEgk BFMc Ndhl GIem HJai CKbn DLfj
28	1	9	AFjn BEae bfim HKcl GLMh CINk DJdg
28	1	9	AIci BJNn EKMj FLdm begl CGaf DHhk
28	1	9	AGbd BHgm ELNi achn FKfk CJej DIMl
28	1	9	AKeh BLbk FIag EJfl Ncjm CHMd DGin
28	1	9	AHNf BGjl FJbh Meik EIdn CLcg DKam
28	1	9	ALal BKdi GJck Mfgn HIbj CEhm DFNe
28	1	9	AJMm BIfh CFil DEbc GKNg HLen adjk.
32	1	10	ABCD EFGH IJKL MNPO abcd efgh ijkl mnop
32	2	10	AEIm BgcH DFKp kPdf Maei ChbG jNoL lJnO
32	3	10	Alof Bhkm DNGi FaLO MbHK CPeJ Ejcp gIdn
32	4	10	AciL BjdK DkbJ FgoP fGOp CIla EhMn NeHm
32	5	10	AgNK BElP DIoH hdiO beLp Cjfm FMcJ kaGn
32	6	10	AhJp BFin DcmO INbf leGK CMod EgkL jPaH
32	7	10	AFde BoGJ DEaf hlNc PiKm CHLn gjbO IkMp
32	8	10	APbn BNap DglM koce fHiJ CEKO FhIj dGLm
32	9	10	AjMG BIeO DhPL gaJm cfKn CFkN Eobi ldHp
32	10	10	AkHO BMfL Djen Flbm IPcG Cgip ENdJ hoaK.
36	1	8	[ [1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16], [17, 18, 19, 20], [21, 22, 23, 24], [25, 26, 27, 28], [29, 30, 31, 32], [33, 34, 35, 36] ]
36	2	8	[ [1, 5, 9, 13], [2, 6, 10, 17], [3, 7, 11, 21], [4, 8, 12, 25], [14, 18, 22, 29], [15, 19, 23, 33], [16, 26, 30, 34], [20, 27, 31, 35], [24, 28, 32, 36] ]
36	3	8	[ [1, 6, 11, 25], [2, 7, 9, 16], [3, 5, 10, 20], [4, 14, 21, 33], [8, 15, 18, 32], [12, 13, 17, 22], [19, 27, 30, 36], [23, 28, 31, 34], [24, 26, 29, 35] ]
36	4	8	[ [1, 10, 18, 21], [2, 8, 13, 29], [3, 14, 31, 36], [4, 9, 20, 23], [5, 15, 17, 28], [6, 12, 16, 19], [7, 26, 32, 33], [11, 24, 27, 34], [22, 25, 30, 35] ]
36	5	8	[ [1, 14, 24, 30], [2, 12, 18, 34], [3, 9, 17, 32], [4, 6, 28, 35], [5, 21, 29, 36], [7, 10, 19, 25], [8, 16, 23, 27], [11, 13, 20, 33], [15, 22, 26, 31] ]
36	6	8	[ [1, 12, 23, 26], [2, 11, 22, 36], [3, 6, 13, 24], [4, 10, 16, 32], [5, 18, 27, 33], [7, 20, 28, 30], [8, 14, 19, 35], [9, 15, 29, 34], [17, 21, 25, 31] ]
36	7	8	[ [1, 19, 28, 29], [2, 5, 23, 30], [3, 12, 15, 27], [4, 11, 18, 31], [6, 9, 26, 36], [7, 14, 17, 34], [8, 10, 22, 33], [13, 21, 32, 35], [16, 20, 24, 25] ]
36	8	8	[ [1, 7, 15, 35], [2, 14, 25, 32], [3, 16, 18, 28], [4, 17, 27, 29], [5, 11, 19, 26], [6, 20, 22, 34], [8, 9, 21, 30], [10, 13, 23, 36], [12, 24, 31, 33] ]
40 (10*4)	Unkn.	5/6ND
44 (11*4)	Dutch	11
52 (13*4)	Dutch	13
68 (17*4)	Dutch	17
76 (19*4)	Dutch	19

League play blocks

Considering that league blocks contain 5 players, the counting mechanism has to be recalculated for Dutch cycles. These numbers are for 6-session events or seasons. These Dutch cycle blocks can drop the last fifth in order to make groups of 4, expanding the solved ranges of players from 80% to 100% of the maximal solutions. For 40, using the social golfer solution below will work for 32 to 40 players. Given the distribution of primes, there is a solution within that 20% range except for 66 and 67 players. A way around it would be to have two "separable" leagues running up to 35 players per side, thus covering 66 and 67.

Players	Round	Of	Match-ups
25	1st	of 6	[ [1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20], [21, 22, 23, 24, 25] ]
25	2nd	of 6	[ [1, 6, 11, 16, 21], [2, 7, 12, 17, 22], [3, 8, 13, 18, 23], [4, 9, 14, 19, 24], [5, 10, 15, 20, 25] ]
25	3rd	of 6	[ [1, 7, 13, 19, 25], [2, 8, 14, 20, 21], [3, 9, 15, 16, 22], [4, 10, 11, 17, 23], [5, 6, 12, 18, 24] ]
25	4th	of 6	[ [1, 8, 15, 17, 24], [2, 9, 11, 18, 25], [3, 10, 12, 19, 21], [4, 6, 13, 20, 22], [5, 7, 14, 16, 23] ]
25	5th	of 6	[ [1, 9, 12, 20, 23], [2, 10, 13, 16, 24], [3, 6, 14, 17, 25], [4, 7, 15, 18, 21], [5, 8, 11, 19, 22] ]
25	6th	of 6	[ [1, 10, 14, 18, 22], [2, 6, 15, 19, 23], [3, 7, 11, 20, 24], [4, 8, 12, 16, 25], [5, 9, 13, 17, 21] ]
30	1st	of 6	[ [1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20], [21, 22, 23, 24, 25], [26, 27, 28, 29, 30] ]
30	2nd	of 6	[ [1, 6, 11, 16, 21], [2, 7, 13, 19, 30], [3, 8, 14, 24, 29], [4, 9, 20, 25, 28], [5, 15, 18, 23, 27], [10, 12, 17, 22, 26] ]
30	3rd	of 6	[ [1, 8, 13, 20, 22], [2, 6, 12, 23, 28], [3, 9, 11, 18, 30], [4, 15, 16, 24, 26], [5, 7, 17, 25, 29], [10, 14, 19, 21, 27] ]
30	4th	of 6	[ [1, 7, 18, 24, 28], [2, 10, 11, 20, 29], [3, 6, 15, 19, 22], [4, 14, 17, 23, 30], [5, 9, 13, 21, 26], [8, 12, 16, 25, 27] ]
30	5th	of 6	[ [1, 10, 15, 25, 30], [2, 9, 17, 24, 27], [3, 7, 12, 20, 21], [4, 6, 13, 18, 29], [5, 14, 16, 22, 28], [8, 11, 19, 23, 26] ]
30	6th	of 6	[ [1, 9, 12, 19, 29], [5, 6, 20, 24, 30], [4, 7, 11, 22, 27], [8, 15, 17, 21, 28], [3, 10, 13, 16, 23], [2, 14, 18, 25, 26] ]
35	all	of 7	Dutch cycles. {28P-35P}
40	1st	of 6	[ [1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20], [21, 22, 23, 24, 25], [26, 27, 28, 29, 30], [31, 32, 33, 34, 35], [36, 37, 38, 39, 40] ]
40	2nd	of 6	[ [1, 6, 11, 16, 21], [2, 7, 12, 26, 31], [3, 8, 13, 17, 36], [4, 9, 14, 27, 32], [5, 10, 15, 22, 37], [18, 23, 28, 33, 38], [19, 24, 29, 34, 39], [20, 25, 30, 35, 40] ]
40	3rd	of 6	[ [1, 7, 14, 17, 22], [2, 6, 13, 28, 34], [3, 10, 11, 27, 40], [4, 8, 12, 20, 33], [5, 9, 16, 25, 39], [15, 21, 29, 31, 38], [18, 24, 26, 35, 36], [19, 23, 30, 32, 37] ]
40	4th	of 6	[ [1, 8, 15, 19, 35], [2, 16, 22, 27, 33], [3, 9, 12, 24, 38], [4, 6, 30, 31, 36], [5, 14, 23, 34, 40], [7, 11, 20, 28, 39], [10, 17, 21, 26, 32], [13, 18, 25, 29, 37] ]
40	5th	of 6	[ [1, 9, 13, 31, 40], [2, 15, 20, 24, 32], [3, 14, 21, 33, 39], [4, 16, 26, 34, 37], [5, 7, 27, 35, 38], [6, 12, 17, 23, 29], [8, 11, 18, 22, 30], [10, 19, 25, 28, 36] ]
40	6th	of 6	[ [1, 10, 12, 18, 39], [2, 9, 11, 23, 35], [3, 6, 15, 25, 26], [4, 13, 19, 22, 38], [5, 17, 24, 30, 33], [7, 16, 29, 32, 40], [8, 14, 28, 31, 37], [20, 21, 27, 34, 36] ]
45	1st	of 6	[ [20, 24, 32, 39, 43], [6, 29, 31, 33, 42], [7, 11, 17, 34, 45], [12, 14, 15, 18, 25], [2, 5, 8, 9, 19], [1, 4, 16, 27, 28], [3, 13, 23, 30, 35], [10, 22, 26, 38, 40], [21, 36, 37, 41, 44] ]
45	2nd	of 6	[ [5, 17, 28, 40, 41], [11, 13, 22, 24, 27], [8, 25, 32, 33, 37], [9, 10, 20, 30, 45], [2, 12, 16, 29, 44], [3, 15, 36, 42, 43], [4, 6, 18, 23, 26], [1, 14, 19, 21, 34], [7, 31, 35, 38, 39] ]
45	3rd	of 6	[ [4, 21, 25, 31, 40], [13, 16, 41, 43, 45], [2, 20, 22, 33, 34], [9, 14, 23, 27, 38], [17, 18, 19, 29, 32], [7, 8, 12, 30, 36], [1, 15, 26, 37, 39], [3, 5, 6, 24, 44], [10, 11, 28, 35, 42] ]
45	4th	of 6	[ [19, 27, 40, 42, 45], [4, 12, 17, 22, 39], [8, 13, 20, 26, 44], [18, 24, 30, 37, 38], [7, 23, 28, 29, 43], [6, 11, 15, 21, 32], [3, 9, 16, 25, 34], [1, 5, 33, 35, 36], [2, 10, 14, 31, 41] ]
45	5th	of 6	[ [4, 7, 9, 15, 41], [11, 25, 26, 29, 36], [8, 16, 18, 39, 40], [27, 30, 31, 34, 44], [14, 22, 35, 37, 43], [5, 12, 13, 21, 42], [6, 19, 20, 28, 38], [1, 2, 3, 32, 45], [10, 17, 23, 24, 33] ]
45	6th	of 6	[ [4, 8, 24, 29, 45], [6, 13, 14, 36, 40], [15, 16, 19, 22, 23], [5, 7, 10, 18, 27], [3, 17, 20, 31, 37], [1, 11, 38, 43, 44], [9, 21, 26, 28, 33], [12, 32, 34, 35, 41], [2, 25, 30, 39, 42] ]
50	all	of 5	Dutch cycles work for 5 sessions only.
50	1st	of 7	[ [5, 16, 18, 25, 29], [1, 7, 27, 42, 46], [4, 6, 15, 21, 41], [3, 11, 26, 30, 32], [9, 19, 24, 37, 38], [8, 13, 33, 43, 45], [35, 40, 47, 48, 49], [17, 23, 31, 34, 50], [2, 12, 14, 20, 36], [10, 22, 28, 39, 44] ]
50	1st	of 7	[ [8, 20, 40, 42, 44], [15, 16, 17, 22, 47], [1, 10, 23, 29, 38], [3, 6, 28, 36, 48], [2, 24, 27, 33, 39], [7, 11, 13, 21, 31], [4, 32, 35, 45, 46], [9, 14, 18, 34, 41], [25, 30, 37, 43, 50], [5, 12, 19, 26, 49] ]
50	1st	of 7	[ [19, 21, 29, 32, 47], [8, 24, 25, 28, 34], [3, 18, 31, 44, 46], [4, 14, 39, 43, 49], [2, 10, 15, 42, 45], [9, 11, 16, 20, 50], [5, 7, 23, 37, 40], [1, 13, 26, 41, 48], [22, 33, 35, 36, 38], [6, 12, 17, 27, 30] ]
50	1st	of 7	[ [10, 14, 16, 21, 26], [23, 25, 36, 39, 42], [9, 13, 32, 44, 49], [3, 5, 8, 22, 27], [4, 11, 17, 38, 40], [12, 24, 43, 46, 48], [2, 7, 19, 41, 50], [1, 18, 28, 30, 33], [6, 34, 37, 45, 47], [15, 20, 29, 31, 35] ]
50	1st	of 7	[ [13, 20, 22, 30, 34], [26, 27, 38, 45, 50], [1, 11, 36, 43, 44], [16, 32, 33, 37, 41], [4, 9, 12, 31, 47], [14, 28, 29, 40, 46], [5, 6, 24, 35, 42], [7, 15, 18, 39, 48], [2, 8, 21, 23, 49], [3, 10, 17, 19, 25] ]
50	1st	of 7	[ [6, 26, 31, 39, 40], [11, 14, 22, 37, 42], [2, 5, 9, 17, 48], [4, 24, 29, 44, 50], [15, 19, 34, 36, 46], [3, 7, 20, 33, 49], [10, 18, 27, 32, 43], [13, 16, 23, 28, 35], [1, 12, 21, 25, 45], [8, 30, 38, 41, 47] ]
50	1st	of 7	[ [11, 18, 23, 24, 47], [22, 31, 41, 45, 49], [3, 9, 21, 40, 43], [2, 6, 13, 38, 46], [14, 25, 27, 35, 44], [12, 15, 28, 32, 50], [4, 5, 10, 33, 34], [7, 8, 26, 29, 36], [1, 17, 20, 37, 39], [16, 19, 30, 42, 48] ]
55	all	of 11	Dutch cycles. {44P-55P}
60	all	of 6	G(25+35) or G(30+30).
65	all	of 13	Dutch cycles. {52P-65P}
70	all	of 7	G(35+35).
75	all	of 6	G(35+40), G(30+45) {both 60P-75P}; G(25+25+25) {72P-75P}.
{5*prime}	all	of {prime}	Dutch cycles. {{4*prime}P-{5*prime}P}; prime>=5. (25 is the special case, where it gets the sixth extra session by virtue of being 25 = 5^2.)

Trying to group a league with a variable amount of entries poses its own challenges. In order to start a league asymmetrically, it is possible to start seeding groups from 17 members and every 5 onward. However, this alone will guarantee that groups can be made but not that no rematches will occur. For an ideal solution like 35, in theory, 7 groups of 4 can use the same solution, however, with 3 groups pre-formed at 27 members, the minimum requirement would be to end up with 31 players [31, 35]. Likewise, for the 55 solution, overloading groups of 5 may render the ability to make 11 groups but with more groups of 4. If [48, 50] players are present, two separate blocks of 24/25 are usable for 6-session seasons.

Min	Groups of 5	Groups of 4	Spare	Max	Comment
27	3	0	12	35	<=30 : 6 groups, >=31 : 7 groups.
32	4	0	12	40	<=35 : 7 groups, >=36 : 8 groups.
37	5	0	12	45	<=40 : 8 groups, >=41 : 9 groups.
42	5	0	17	50	<=45 : 9 groups, >=46 : 10 groups.
48	7	0	12	50	<=50 : 10 groups in 25s, >=51 : 11 groups in 55.
52	7	0	17	60	<=55 : 11 groups in 55, >=56 : 12 groups in 25 and 35.
57	8	0	17	60	<=60 : 12 groups in 25 and 35, >=61 : 14 groups in 35s (5*8 + 4*4 + 5*1).
62	10	0	12	60	<=65 : 13 groups, >=66 : 14 groups.
67	11	0	12	60	<=70 : 14 groups, >=71 : 15 groups.
72	12	0	12	60	<=75 : 15 groups, >=76 : 16 groups.

X-player season

Min. Players	Max Players	Mechanism	Comment
10	10	5P randomize	Repeats will forcibly occur.
11	12	Not possible	With thirds promotion, 10 in top group, 18 in next, top group gets 13+.
13	15	Mix and randomize	Repeats will forcibly occur.
16	16	4P perfect + Siberian or Random (6th)	5 sessions covered, 6th pairing could be done randomly at the start or drawn later (at a pre-announced time) relative to current ranking.
17	23	Mix and randomize	Repeats will most likely occur.
24	25	5P perfect	For 24 players, ignore 25th player in grid, those sessions are 4P
26	27	Mix and randomize	{TBD.}
28	28	Use 4P
29	30	Use 5P	For 29 players, ignore 30th player in grid, those sessions are 4P
31	35	Use 5P grid for 35
36	40	Use 5P grid for 40	Grid can ignore last 5 players.

WAML-relevant summary

If we can get player blocks of 25♥, 35, 40, 55 (even 65) or sums of their multiples (60♥ = 25♥ + 35; 65 = 25♥ + 40; 70 = 35 + 35; 75yes; 80yes; 85♥♥yes; 90yes; 95yes; 100♥yes; ...) or a number significantly close, 80% + 4 per heart, then we can cover the whole span from 48+ if we stop forming asymmetrical groups after 4 are made. A fifth group can be drawn at 57 with no dificulty.