Effective Hand Strength (EHS) is a poker algorithm conceived by computer scientistsDarse Billings, Denis Papp, Jonathan Schaeffer and Duane Szafron that has been published for the first time in a research paper (1998). 'Opponent Modeling in Poker'(PDF). AAAI-98 Proceedings.

Welcome » On this site you can find all possible combinations of preflop hands that can occur in Texas Hold'em Poker. As a bonus you will also learn the nicknames of the different hands. The hands are ranked from #1 to #169, where #1 is the best. This ranking is applicable when the poker table is full ring (9-10 people). Sep 30, 2019 Six-Player Power Ratings in Texas Hold ’Em Introduction. The following table ranks the top hands in a 6-player game. This table assumes that all players stay in until the end. Explanation of column headings: Cards: Initial two-card hand. Probability of win: Probability that this hand will.

It has since then been considered as a reference in the realm of poker artificial intelligence and has been the basis of further research such as:

'Computer poker: a review'(PDF). Artificial Intelligence, Department of Computer Science, University of Auckland, New Zealand: 962–963. 2010.
'Application of AI in poker'(PDF). VU University Amsterdam Faculty of Sciences: 12–13. 2011.
'Advances in artificial intelligence – SBIA 2008 : 19th Brazilian Symposium on Artificial Intelligence, Salvador, Brazil, October 26–30, 2008 ; proceedings'. 2008: 85–86.Cite journal requires |journal= (help)

Algorithm[edit]

The algorithm is a numerical approach to quantify the strength of a poker hand where its result expresses the strength of a particular hand in percentile (i.e. ranging from 0 to 1), compared to all other possible hands.The underlying assumption is that an Effective Hand Strength (EHS) is composed of the current Hand Strength (HS) and its potential to improve or deteriorate (PPOT and NPOT):

{displaystyle EHS=HStimes (1-NPOT)+(1-HS)times PPOT}

where:

${displaystyle EHS}$ is the Effective Hand Strength
${displaystyle HS}$ is the current Hand Strength (i.e. not taking into account potential to improve or deteriorate, depending on upcoming table cards
${displaystyle NPOT}$ is the Negative POTential (i.e. the probability that our current hand, if the strongest, deteriorates and becomes a losing hand)
${displaystyle PPOT}$ is the Positive POTential (i.e. the probability that our current hand, if losing, improves and becomes the winning hand)

Pseudocode[edit]

Hand Strength (HS) will enumerate all possible opponent hand cards and count the occurrences where our hand is strongest (+50% of the cases where we are tied):

Texas Holdem Poker Hand Rankings

In addition, EHS will consider the hand potential (i.e. its probabilities to improve or deteriorate):

Applicability[edit]

EHS is applicable to a wide variety of poker games such as Texas hold 'em poker, Omaha hold 'em poker, ...

Given the complexity of the algorithm, it can not be computed manually and has to be used in an Artificial Intelligence context.

Texas Holdem Hand Strength Chart

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