Bartolin

16-09-2007, 07:03 PM

Hi,

I would like to pick up a question discussed in the thread "Another sp error?" (http://chesschat.org/showthread.php?t=6619), namely: How should B3-B6 be incorporated into the pairing procedure given by C, especially C6?

There were a lot of useful remarks about this question before the thread moved in another direction. There is still an unanswered question waiting in that thread and I don't want to stop that discussion due to asking a completely different question. Therefore I opened this new thread. If this is regarded as bad practice, I beg your pardon.

Back to my question about B3-B6. Basically, there were two different positions:

1. C6 could be interpreted literal. That would mean that only B1 and B2 must be

fulfilled -- violations of B3 to B6 are irrelevant, since they aren't mentioned

in C6. (compare http://chesschat.org/showpost.php?p=167008&postcount=15,

http://chesschat.org/showpost.php?p=167079&postcount=21)

2. C6 could be seen as badly worded; it really should refer to B1 to B6 instead of just B1 to B2. This view is conform with section B, which states that "[B3 to B6] should be fulfilled as much as possible. To comply with these criteria, transpositions or even exchanges may be applied, but no player should be moved down to a lower score bracket." Bill Gletsos said that all FIDE approved programs act this way. (cp. http://chesschat.org/showpost.php?p=167088&postcount=22 and http://chesschat.org/showpost.php?p=167092&postcount=25).

If one takes the second position (and I think, it's the more convincing one), there remains the question, how B3 is to be incorporated in a pairing algorithm (http://chesschat.org/showpost.php?p=167008&postcount=15).

It has been pointed out that B3 is relevant only for heterogeneous groups or for groups that are actually heterogeneous, but are treated as homogeneous according to A3 (http://chesschat.org/showpost.php?p=167071&postcount=17).

Does one have to ignore the procedure from C for those groups and instead:

1. compute all possible pairings for those groups (by allowing transpositions and exchanges) first

2. check which fits best with B3 (let's assume, B3 refers to the sum of score differences)

3. if there are several pairings which are "best" according to B3, check which fits best with B4

4. if there are several pairings which fit with B4, check which fits best with B5

5. if there are several pairings which fit with B5, check which fits best with B6

6. if there are several pairings which fit with B6, return to C, apply the procedure and check, which one is obtained first?

This doesn't sound like a smart algorithm to me.

But enough of theoretical questions, here is an example. It's from a real tournament and trying to re-pair it, the above questions arose.

Round 4 Pairing Groups

-------------------------------------------------------------------------

Place No Opponents Roles Float Score

1

8 18,5,3 BWB D 3

2

1 11,10,6 WBW u 2.5

3-8

2 12,7,9 BWB 2

4 14,9,7 BWB 2

5 15,8,13 WBW 2

7 17,2,4 WBW 2

9 19,4,2 WBW 2

17 7,14,12 BWB D 2

9-14

3 13,6,8 WBW U 1.5

6 16,3,1 BWB 1.5

10 20,1,15 BWB 1.5

11 1,12,16 BWB d 1.5

15 5,20,10 BWW 1.5

16 6,19,11 WBW 1.5

15-17

13 3,18,5 BWB 1

19 9,16,14 BWB 1

20 10,15,18 WBB 1

18

12 2,11,17 WBW U 0.5

19-20

14 4,17,19 WBW 0

18 8,13,20 WBW 0

In the tournament the pairings were: 8-1, 2-5, 4-17, 9-7, 11-3, 6-15, 10-16, 13-19, 20-12 and 18-14.

The first 8 pairings are reasonably clear, but how to get the last two pairings.

20 is downfloated to 12, forming a score bracket (a homogeneous one, according to A3, last sentence). Unfortunately, 12 was upfloated two times. Therefore, 20-12 doesn't seem to fit according to C1-C9. Next, C10 doesn't seem to be relevant, since we don't have a homogeneous remainder group. Next, C11 applies, but increasing x doesn't help. Next C12 doesn't apply. Neither does C13. Therefore we arrive at C14, decrease p by 1 (to 0) and move both players down to a joined score bracket 20,12,14,18.

First question: Doesn't that contradicts with B, saying about Relative Criteria B3-B6: "no player should be moved down to a lower score bracket"? According to B, 20-12 seems to be a correct pairing -- even if one doesn't arrive there according to C. At what point of the pairing procedure should a computer program consider this?

But let's assume, 20 and 12 are to be moved down. Now S1 becomes 20,12 and S2 14,18. The first pairings one arrives with are 20-14 and 18-12. Those are fine as long one ignores B3. (For 20-14 there is a score difference of 1, for 12-18 the score difference is 0.5.) Better pairings are of course 20-12 (sic!) and 18-14. But again: At what point of the pairing procedure should a computer program consider this?

By the way: I tried to re-pair the given tournament with Games::Tournament::Swiss (http://search.cpan.org/~drbean/Games-Tournament-Swiss-0.08/) and it gave the pairings 20-14 and 18-12 for the last two boards. That is because it takes C6 literal and ignores B3.

I hope my questions aren't stupid. I don't have experience with the pairing rules, but I really want to understand them. (And I want to improve the pairing algorithm of Games::Tournament::Swiss.)

Thanks

Christian

I would like to pick up a question discussed in the thread "Another sp error?" (http://chesschat.org/showthread.php?t=6619), namely: How should B3-B6 be incorporated into the pairing procedure given by C, especially C6?

There were a lot of useful remarks about this question before the thread moved in another direction. There is still an unanswered question waiting in that thread and I don't want to stop that discussion due to asking a completely different question. Therefore I opened this new thread. If this is regarded as bad practice, I beg your pardon.

Back to my question about B3-B6. Basically, there were two different positions:

1. C6 could be interpreted literal. That would mean that only B1 and B2 must be

fulfilled -- violations of B3 to B6 are irrelevant, since they aren't mentioned

in C6. (compare http://chesschat.org/showpost.php?p=167008&postcount=15,

http://chesschat.org/showpost.php?p=167079&postcount=21)

2. C6 could be seen as badly worded; it really should refer to B1 to B6 instead of just B1 to B2. This view is conform with section B, which states that "[B3 to B6] should be fulfilled as much as possible. To comply with these criteria, transpositions or even exchanges may be applied, but no player should be moved down to a lower score bracket." Bill Gletsos said that all FIDE approved programs act this way. (cp. http://chesschat.org/showpost.php?p=167088&postcount=22 and http://chesschat.org/showpost.php?p=167092&postcount=25).

If one takes the second position (and I think, it's the more convincing one), there remains the question, how B3 is to be incorporated in a pairing algorithm (http://chesschat.org/showpost.php?p=167008&postcount=15).

It has been pointed out that B3 is relevant only for heterogeneous groups or for groups that are actually heterogeneous, but are treated as homogeneous according to A3 (http://chesschat.org/showpost.php?p=167071&postcount=17).

Does one have to ignore the procedure from C for those groups and instead:

1. compute all possible pairings for those groups (by allowing transpositions and exchanges) first

2. check which fits best with B3 (let's assume, B3 refers to the sum of score differences)

3. if there are several pairings which are "best" according to B3, check which fits best with B4

4. if there are several pairings which fit with B4, check which fits best with B5

5. if there are several pairings which fit with B5, check which fits best with B6

6. if there are several pairings which fit with B6, return to C, apply the procedure and check, which one is obtained first?

This doesn't sound like a smart algorithm to me.

But enough of theoretical questions, here is an example. It's from a real tournament and trying to re-pair it, the above questions arose.

Round 4 Pairing Groups

-------------------------------------------------------------------------

Place No Opponents Roles Float Score

1

8 18,5,3 BWB D 3

2

1 11,10,6 WBW u 2.5

3-8

2 12,7,9 BWB 2

4 14,9,7 BWB 2

5 15,8,13 WBW 2

7 17,2,4 WBW 2

9 19,4,2 WBW 2

17 7,14,12 BWB D 2

9-14

3 13,6,8 WBW U 1.5

6 16,3,1 BWB 1.5

10 20,1,15 BWB 1.5

11 1,12,16 BWB d 1.5

15 5,20,10 BWW 1.5

16 6,19,11 WBW 1.5

15-17

13 3,18,5 BWB 1

19 9,16,14 BWB 1

20 10,15,18 WBB 1

18

12 2,11,17 WBW U 0.5

19-20

14 4,17,19 WBW 0

18 8,13,20 WBW 0

In the tournament the pairings were: 8-1, 2-5, 4-17, 9-7, 11-3, 6-15, 10-16, 13-19, 20-12 and 18-14.

The first 8 pairings are reasonably clear, but how to get the last two pairings.

20 is downfloated to 12, forming a score bracket (a homogeneous one, according to A3, last sentence). Unfortunately, 12 was upfloated two times. Therefore, 20-12 doesn't seem to fit according to C1-C9. Next, C10 doesn't seem to be relevant, since we don't have a homogeneous remainder group. Next, C11 applies, but increasing x doesn't help. Next C12 doesn't apply. Neither does C13. Therefore we arrive at C14, decrease p by 1 (to 0) and move both players down to a joined score bracket 20,12,14,18.

First question: Doesn't that contradicts with B, saying about Relative Criteria B3-B6: "no player should be moved down to a lower score bracket"? According to B, 20-12 seems to be a correct pairing -- even if one doesn't arrive there according to C. At what point of the pairing procedure should a computer program consider this?

But let's assume, 20 and 12 are to be moved down. Now S1 becomes 20,12 and S2 14,18. The first pairings one arrives with are 20-14 and 18-12. Those are fine as long one ignores B3. (For 20-14 there is a score difference of 1, for 12-18 the score difference is 0.5.) Better pairings are of course 20-12 (sic!) and 18-14. But again: At what point of the pairing procedure should a computer program consider this?

By the way: I tried to re-pair the given tournament with Games::Tournament::Swiss (http://search.cpan.org/~drbean/Games-Tournament-Swiss-0.08/) and it gave the pairings 20-14 and 18-12 for the last two boards. That is because it takes C6 literal and ignores B3.

I hope my questions aren't stupid. I don't have experience with the pairing rules, but I really want to understand them. (And I want to improve the pairing algorithm of Games::Tournament::Swiss.)

Thanks

Christian