Error Calculating Hand Strength for OmahaEightOrBetterLowHand

[pauldalewilliams]

I was trying to use this to calculate Omaha High Low hand strengths but I think I ran into a bug:

import pokerkit as pk

pk.calculate_hand_strength(
    3,
    pk.parse_range('AsAd3d2s'),
    pk.Card.parse('4s8c3s'),
    4,
    5,
    pk.Deck.STANDARD,
    (pk.hands.OmahaEightOrBetterLowHand,),
    sample_count=700,
)

results in this error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\pdw\code\bp\Lib\site-packages\pokerkit\analysis.py", line 403, in calculate_hand_strength
    equities = calculate_equities(
               ^^^^^^^^^^^^^^^^^^^
  File "C:\Users\pdw\code\bp\Lib\site-packages\pokerkit\analysis.py", line 324, in calculate_equities
    for i, equity in chain.from_iterable(map(enumerate, mapper(fn, indices))):
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\pdw\code\bp\Lib\site-packages\pokerkit\analysis.py", line 208, in __calculate_equities_1
    return __calculate_equities_0(
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\pdw\code\bp\Lib\site-packages\pokerkit\analysis.py", line 182, in __calculate_equities_0
    hands = list(
            ^^^^^
  File "C:\Users\pdw\code\bp\Lib\site-packages\pokerkit\hands.py", line 542, in from_game
    raise ValueError(
ValueError: No valid ABCMeta hand can be formed from the hole and board cards.

It seems like the evaluation for low hands isn't properly calculating the "max_hand" as best as I can tell from digging in the code. But I have no idea what to test next - none of my attempts to fix it have worked so far. Any suggestions or am I just doing something wrong?

It works great for OmahaHoldemHand, so thank you for that!

[pauldalewilliams]

Ah, I think I'm on to something - the problem may be with what happens when the random hands generated can't create a valid low hand:

pk.calculate_equities(
    (pk.parse_range('3d2sAsAd'),
     pk.parse_range('5dJcQcKd'),
    ),
    pk.Card.parse('8c4s3s'),
    4,
    5,
    pk.Deck.STANDARD,
    (pk.hands.OmahaEightOrBetterLowHand,),
    sample_count=700,
)

fails but this one works:

pk.calculate_equities(
    (pk.parse_range('3d2sAsAd'),
     pk.parse_range('5d3cAcKd'),
    ),
    pk.Card.parse('8c4s3s'),
    4,
    5,
    pk.Deck.STANDARD,
    (pk.hands.OmahaEightOrBetterLowHand,),
    sample_count=700,
)

This is the most direct route to triggering the error:

pk.OmahaEightOrBetterLowHand.from_game('5dJcQcKd','8c4s3s')

For my purposes, I managed to work around it by modifying hands.py BoardCombinationHand and HoleBoardCombinationHand to go from:

            except ValueError:
                pass
            else:
                if max_hand is None or hand > max_hand:
                    max_hand = hand

        if max_hand is None:
            raise ValueError(
                (
                    f'No valid {type(cls).__qualname__} hand can be formed'
                    ' from the hole and board cards.'
                ),
            )

        return max_hand

to this:

            except ValueError:
                pass
            else:
                #if max_hand is None or hand > max_hand:
                if hand is not None and (max_hand is None or hand > max_hand): # added by PDW
                    max_hand = hand

        #if max_hand is None:
        if max_hand is None and not cls.low: # added by PDW
            raise ValueError(
                (
                    f'No valid {type(cls).__qualname__} hand can be formed'
                    ' from the hole and board cards.'
                ),
            )

        return max_hand

I'm sure this isn't a valid permanent fix but I'm sharing what I found as the root cause - EightOrBetterLookup adds no entries for non-qualifying hands because it generates a ValueError it tries to create an instance of the Hand class and the init fails on the self.lookup.has_entry(self.cards) call on line 90 of hands.py.

[AussieSeaweed]

Hi,

Sorry for the late response. Thanks for sharing this!

Also, I find the error message containing 'ABCMeta' to be problematic. It should be the actual hand class.

I will think of ways to fix this... I think the change can be isolated to pokerkit/analysis.py.

I don't have the bandwidth to work on this right now, but will aim to get this done by early November.

Thanks!

[pauldalewilliams]

No worries! My fix is working for my purposes but I'm mainly using it for the equities/hand strength anyway, so I'm not worried about side effects (yet...). Thanks for your work on this!