Edge Conditions in Razz Showdowns
Thursday, 21 December 2006 11:40![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
shipitfishA good friend of mine and lurker here at my journal is a software developer for a startup online poker site. I have served from time to time as their “poker world expert”, which I've enjoyed immensely. These days, they are all accomplished low limit players themselves and don't need my expertise often, but my friend sent me this question that I think I have an answer for, but am curious what others think.
They are implementing Razz, and like all good programmers, they are making sure that every edge condition is handled. My friend has discovered a case where the otherwise excellent Poker Source hand evaluation library (which folks in the poker world who don't also live in the Software Freedom world know as “twodimes”, a web repackager of that library) does something suspicious. We are trying to decide what the right solution is.
Suspend your disbelief for the moment, and consider two Razz hands that
have gotten to showdown heads-up. One hand is the 5
Poker Source says that the winner is the latter hand. I disagree, I think the former wins. In Razz, we have all learned the rule “best five low cards, aces play low, straights and flushes do not count against you“. We've also learned that if all players at showdown must make at least one pair (because they paired twice, for example), the lowest pair wins. I would argue that this continues on up through the rankings of poker hands, skipping the straights and flushes. So, if all players in the hand must make at least two pair, they should make the lowest two pair they can. By this logic, sixes-up is a worse hand than eights-up, and therefore sixes-up should win.
I am not sure what case could be made for declaring the latter hand the winner. It can make four different five card poker hands: eights-up, nines-up, nines-full-of-eights and nines-full-of-fours. The other hand can also make four: sixes-up, sevens-up, sevens-full-of-sixes and sevens-full-of-fives. Can anyone therefore speculate why Poker Source would think the latter hand is a winner in Razz? Is it just a bug, or are we missing something?
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no subject
Date: 2006-12-21 18:12 (UTC)I'm not saying this means of evaluation is right, but that was my thinking on...uh...its thinking. :)
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Date: 2006-12-21 20:56 (UTC)This theory would dovetail nicely into the philosophy that we often apply to Razz hand evaluation when everyone has paired twice (i.e., lowest pair wins).
I think you've discovered correctly the reason the hand evaluation library does what it does (it must have a rule that says: . So, we know what it's doing, but is that right? This remains the question.
I should point out that if we step back a moment to 2-7 lowball games, where straights and flushes do count against you, I think everyone would argue the rule stated above would make no sense. I guess the question is:
Of course, only programmers would ask this question, because the number of times in real life where two hands of this nature get to show down are so statically low that it could easily be the case that this has never happened in any Razz game that humans ever played.
no subject
Date: 2006-12-21 22:20 (UTC)It might be slightly more complicated than that. Razz hands only make four distinct traditional poker hands: no pair, one pair, two pair, or a full house (in particular, you can't make trips or quads). Evaluating the first two is well understood and, really, the only case that comes up in real play. For two pair, I like the previous commenter's strategy of calling, say, JJ33x, "threes-down," and ranking that better than 9944x. Nevertheless, one could argue for having it the other way 'round, I suppose.
Razz full houses are a degenerate case: the only way you make one is to have a hand of the form WWWWXXX. If another player has YYYYZZZ, the winner should simply be the hand that contains the lowest rank among W, X, Y, and Z (see below).
Robert's Rules seem to imply that normal poker rankings apply in reverse (other than the business of aces being low and the lack of straights and flushes). This would mean pokersource is broken in even the two pair case.
I am almost certain pokersource's handling of extremely poor Razz hands is buggy anyway, though. For example, it says that KKKK333 beats 2222444 but loses to 4444222. The first seems wrong to me. Both hands are Razz full houses. If you choose to rank a full house on the lowest trips followed by the lowest pair, the first pair of hands would be 333KK and 22244; if you do it the other way 'round, the hands are KKK33 and 44422; either way, 2222444 beats KKKK333.
I think I would be embarrassed to report this bug.
A very simple answer
Date: 2006-12-22 03:13 (UTC)If after removing straights and flushes, if hand X beats hand Y under normal poker rules, the hand Y beats hand X under razz.
There should *never* be a case where one hand wins over another in both normal poker rules and razz (after removing straights and flushes).
It's as simple as that.
Therefore, 6s full of 5s loses 4s full of 8s in razz and likewise by the same logic 6s and 5s beat 4s and 8s in razz.
4s and 8s should definately *NOT* beat 6s and 5s in both 7-card stud and razz. If one hand wins in 7-card stud, the other hand wins in razz. It is that simple.
no subject
Date: 2006-12-22 17:31 (UTC)Like many others, my vote is no; I think you are correct and that eights-up should lose to sixes-up. Like the anon reply to your comment, I believe Robert's Rules imply that the mechanism for ranking two-pair hands in Razz is no different than in other poker games, save that the lower hand wins. In any case, it looks like this issue is being looked at/resolved already, so...yeah. :)
Why the first hand wins in razz
Date: 2006-12-21 21:46 (UTC)5555666 vs. 4444888
In razz to determine the winner, it is an easy two-step process. The fist step is to make the lowest 5 card hand possible with the 7 cards you have available. After step 1 we have:
55566 vs 44488
Next we see which of these hands would win under normal poker rules after removing straights and flushes. This gives us: 5s full vs 4s full. In normal poker rules the 5s full wins.
Finally, we take the lowest of the two hands for razz which is 4s full. Therefore in razz 4s full beats 5s full.
The same logic must be applied to the two-pair case. Under normal poker rules you consider both pair together as a single ranking. 6s up vs 8s up. In razz you do the opposite, so 6s up wins over 8s up in razz.
I like the concept of a "4s down vs 5s" down, but this logic does not work. If you applied that logic to the full house case, you could argue that KKK22 beats 33344 because the 2s are lower than the 3s. This obviously is incorrect.
I hope I've made this clear.
no subject
Date: 2006-12-21 22:40 (UTC)no subject
Date: 2006-12-22 00:16 (UTC)/* TODO -- review and fix code for hands with >5 cards, in particular
21: hands like KK77442, KKK7733, 777KK33, 333KK77, 4444KKK. */
http://cvs.gna.org/cvsweb/poker-eval/include/inlines/eval_low.h?rev=1.7;cvsroot=pokersource
I'll fix this.
Loic.
no subject
Date: 2006-12-22 00:27 (UTC)no subject
Date: 2006-12-22 00:29 (UTC)Bring-In Ties
Date: 2006-12-22 04:01 (UTC)In 7-card stud, bring-in ties are broken by suit rank (I'm not sure of the exact rank used).
In razz ties are broken by the person sitting closest to the dealer's left.
Re: Bring-In Ties
Date: 2006-12-22 16:46 (UTC)no subject
Date: 2006-12-22 16:46 (UTC)Actually, Loic is the friend that I left unnamed in the original post, whom I now mention by name since he identified himself in another comment. :) I've never dug in the poker source code, so I was just thinking of it from the black box perspective. Of course, I should have UTSL'd, I am glad someone is. :)
no subject
Date: 2010-11-15 03:26 (UTC)5 card stud (http://poker.winner.com/5_card_stud.html)