rescoring and walkovers

[a5sk4s]

the recent enhancement to allow rescoring under certain conditions (see: tournament-js/tournament#20) fails if either left or down is a walkover game - the down case can occur in the first round of double elimination tournaments

is it sufficient fix the criteria in the _safe routine for the walkover games, by looking one level deeper?

[clux]

That's interesting, if so then a _safe fix is in order.

Could you be a little more specific about the case you are looking at?

For a 5 player double elimination I can rescore the match that send a player down to a WO match in LB fine. Otherwise, if right is a WO match, then so is the current one so you cannot rescore it anyway. Unless I am missing something.

[a5sk4s]

This was my manual test with a 5 player tournament:

d = new Duel(5, { last: Duel.LB });
d.score({ s: 1, r: 1, m: 2 }, [0,1]);
d.unscorable({ s: 1, r: 1, m: 2 }, [1,0]);
'S1 R1 M2 cannot be re-scored'

m = d.findMatch({ s: 1, r: 1, m: 2 });
d._safe(m)
false

This is the relevant part of the loser bracket before

  { id: { s: 2, r: 1, m: 1 },
    p: [ -1, 0 ],
    m: [ 0, 1 ] },
  { id: { s: 2, r: 1, m: 2 },
    p: [ -1, -1 ],
    m: [ 0, 1 ] },
  { id: { s: 2, r: 2, m: 1 },
    p: [ 0, 0 ] },
  { id: { s: 2, r: 2, m: 2 },
    p: [ -1, 0 ] },

and after the d.score({ s: 1, r: 1, m: 2 }, [0,1]); call

  { id: { s: 2, r: 1, m: 1 },
    p: [ -1, 5 ],
    m: [ 0, 1 ] },
  { id: { s: 2, r: 1, m: 2 },
    p: [ -1, -1 ],
    m: [ 0, 1 ] },
  { id: { s: 2, r: 2, m: 1 },
    p: [ 0, 5 ] },
  { id: { s: 2, r: 2, m: 2 },
    p: [ -1, 0 ] },

I think the fact that match { s: 2, r: 1, m: 1 } is a walkover match interferes with the re-scoring.

Please let me know if I can help in any other way.

[clux]

Oh yeah, I see now. This is a nice find.

Since .score will change both LBR1M1 and LBR2M1 correctly so it's only an unscorable problem with the new fine grained access control in the _safe virtual. We want to ensure that the LBR2M1 match is not already scored before we blindly allow re-scoring WBR1M2.

Technically it is impossible for the relevant LBR2 match to be scored without also the WBR2 match right of the one we are re-scoring in WBR1 to also be scored. Unfortunately, a similar argument does not hold if you drop on top of a WO marker in LBR2 from WBR2 (then you can have played LBR3 match without WBR3 being touched). Thus, no short-cuts can be really be made; _safe must always check [right, down, down ∘ right] are all unplayed when exists (similar to how _progress does it).

I'll make a fix for this soon. Have written up a test for the cases discussed. Thanks for reporting this 👍

[clux]

Fixed in duel@3.0.1

Thanks again :]

[a5sk4s]

Your welcome. It's been my pleasure. Thanks for the quick turnaround.