# Thread: Sonneborn-Berger tie-break in Vega

1. ## Sonneborn-Berger tie-break in Vega

I have just noticed what seems to be a small bug in Vega's calculation of Sonneborn-Berger scores. Specifically, half-point byes are treated as wins against the virtual opponent, rather than draws.

Originally Posted by FIDE Handbook, C.02. Standards of Chess Equipment, venue for FIDE Tournaments, rate of play and tie-break regulations
13.15.2. For tie-break purposes a player who has no opponent will be
considered as having played against a virtual opponent who has
the same number of points at the beginning of the round and
who draws in all the following rounds. For the round itself the
result by forfeit will be considered as a normal result.

This gives the formula:

Svon = SPR + (1 – SfPR) + 0.5 * (n – R)

where for player P who did not play in round R:
n = number of completed rounds
Svon = score of virtual opponent after round n
SPR = score of P before round R
SfPR = forfeit score of P in round R
Here is a Vega output (Vega 8.2.1):

Code:
```2019 Southern Suburbs Championship
Cross Table at round 7 sorted by score

Pos NAME                           Rtg   T  Fed  Pts |   1     2     3     4     5     6     7    |  DirE    Mwns    MBlk    Buc1    BucT     S-B
---------------------------------------------------------------------------------------------------------------------------------------------------
1 Hardegen,Kathryn               2045 WFM  WA  6.5 | +B12  +W11  +W5   =B2   +W4   +B6   +W7    |    0.5      6      3    27.5    31.0   27.75
2 Ferozkohi,Ihsan                2309      WA  6.5 | +W18  +BYE  +B6   =W1   +W10  +B4   +B5    |    0.5      6      3    27.0    30.0   26.75
3 Holland,Dennis                 1957      WA  5.0 | +W7   =B19  +W13  -B4   =W15  +B16  +W12   |    0.0      4      3    22.0    24.5   17.00
4 Kuan,Han Sen                   2105      WA  4.5 | =BYE  +B17  +W19  +W3   -B1   -W2   +B15   |    0.0      4      3    28.0    30.5   17.50
5 Hare,Tim                       2175      WA  4.5 | +B9   +W10  -B1   +W11  +W8   =B15  -W2    |    0.0      4      3    27.5    31.0   16.25
6 Calado,Edward                  2070      WA  4.5 | +W23  +B16  -W2   =B15  +W19  -W1   +B10   |    0.0      4      3    25.5    27.5   12.75
7 Prunty,Jon                     1508      WA  4.0 | -B3   -W9   +B24  +W22  +B11  +W8   -B1    |    1.0      4      4    24.5    25.5   10.50
8 Ayling,Simon D                 1922      WA  4.0 | +B14  -BYE  +W9   +W12  -B5   -B7   +W16   |    0.0      4      3    23.5    26.5   13.50
9 Gao,Oscar                      1596      WA  3.5 | -W5   +B7   -B8   -W17  +B20  +W22  =B11   |    0.0      3      4    21.5    23.5   10.25
10 Soutar,Gavin                   1805      WA  3.5 | +BYE  -B5   +W23  +W14  -B2   =B12  -W6    |    0.0      3      3    25.5    27.5   10.25
11 De Heer,Alex                   1643      WA  3.5 | +W22  -B1   +W17  -B5   -W7   +B13  =W9    |    0.0      3      3    25.0    27.0   10.25
12 Sheridan,Wallace               1515      WA  3.5 | -W1   +B22  +W16  -B8   +BYE  =W10  -B3    |    0.0      3      3    25.0    27.0    9.75
13 Andrew,Christopher-Jack         959      WA  3.5 | =BYE  +W20  -B3   -B16  +W21  -W11  +B18   |    0.0      3      3    20.5    23.0   11.50
14 Hu,Tommy                       1500     AUS  3.5 | -W8   +B18  +W21  -B10  =BYE   --   +W20   |    0.0      3      2    20.5    23.0   11.50
15 Geronimo,Brent                 1778      WA  3.5 | -W17  +B21  +BYE  =W6   =B3   =W5   -W4    |    0.0      2      2    24.5    27.0   12.50
16 McAteer,Ian                    1736      WA  3.0 | +B24  -W6   -B12  +W13  +B17  -W3   -B8    |    0.0      3      4    23.5    24.5    7.50
17 Brown,Amy                      1248      WA  3.0 | +B15  -W4   -B11  +B9   -W16  -W18  +B24   |    0.0      3      4    21.0    22.0    8.00
18 Simonds,Marcus                 1632      WA  3.0 | -B2   -W14  -B20  +BYE  +W25  +B17  -W13   |    0.0      3      3    20.5    21.5    5.50
19 Gunawan,Tjermin            (W) 1668      WA  2.5 | +B25  =W3   -B4   +W20  -B6    --    --    |    0.0      2      3    24.0    25.0    6.00
20 Gough,Dylan                    1688      WA  2.5 | =W21  -B13  +W18  -B19  -W9   +BYE  -B14   |    0.0      2      3    18.5    20.5    6.25
21 Geronimo,Harry                 1131      WA  2.5 | =B20  -W15  -B14  +BYE  -B13  -W24  +BYE   |    0.0      2      3    16.5    17.5    4.75
22 Zhang,Emily                     596      WA  2.0 | -B11  -W12  +BYE  -B7   +W24  -B9   -BYE   |    0.0      2      3    19.5    20.5    3.00
23 Gunawan,Marco              (W) 1582      WA  2.0 | -B6   +W24  -B10  +W25  -BYE   --    --    |    0.0      2      2    19.5    20.5    2.00
24 Morrison,Robert                1136      WA  1.0 | -W16  -B23  -W7   -BYE  -B22  +B21  -W17   |    0.0      1      3    17.0    19.0    2.50
25 Howard,Bryan               (W) 1129      WA  1.0 | -W19  +BYE  -BYE  -B23  -B18  -BYE   --    |    0.0      1      2    16.5    18.5    2.50

Generated by Vega - www.vegachess.com
(copy licensed to: Perth Southern Suburbs Chess Club - AUS)```
#4 (Kuan, Han Sen) had a half-point bye in Round 1 which, at the close of the tournament, should be treated as a draw against a virtual opponent with score 3.5/7. We can manually calculate Kuan's Sonneborn-Berger score as follows:

S-B = 0.5 * 3.5 + 1 * 3.0 + 1 * 2.5 + 1 * 5.0 + 0 * 6.5 + 0 * 6.5 + 1 * 3.5 = 15.75.

Whereas Vega gives S-B = 17.5, which is what we would get if we replace the Round 1 term in the above sum by 1 * 3.5. Other examples within this tournament also show this to be happening.

2. Hello,

Without to see the file and how the tournament was set is difficult to say anything. However, before to do that sum there is a preliminary task that should be done and it seems you have not performed:
You need to ADJUST the score used for the tie-break. In fact there are many unplayed games and all need to be considered DRAW. Only then you can do the sum.
For example Gunawan has 3.5 tiebreack score and not the real 2.5, and so on.

Here http://www.vegachess.com/ns/node/22 you can find a powerpoint that shows how to apply the rule (bottom page kallithea rule).
Unfortunately the document is in Italian, however from slide 8 the example should be understood without problems.

Please send me the file of that tournament and I'll inquire better.
Thanks,
Luigi

3. This has been fixed in version 8.2.3 released 19th January.

4. Originally Posted by Bill Gletsos
This has been fixed in version 8.2.3 released 19th January.
Hi Bill,
The version available for download from http://www.vegachess.com/ns/node/4 is still 8.2.2. How does one go about getting 8.2.3? I am using Windows 64 bit. Thanks.

UPDATE: I just saw a Vega thread with latest releases where this query might better belong, but it does not answer my question.

Hi Bill,
The version available for download from http://www.vegachess.com/ns/node/4 is still 8.2.2. How does one go about getting 8.2.3? I am using Windows 64 bit. Thanks.

UPDATE: I just saw a Vega thread with latest releases where this query might better belong, but it does not answer my question.
Why do you claim it is still 8.2.2?

6. Originally Posted by Bill Gletsos
Why do you claim it is still 8.2.2?
I'll try again. Maybe something went wrong...

7. My apologies, Bill.
This time I temporarily disabled Norton Security and I have got 8.2.3.
Thanks, mate.

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