monty

monty is a Java 22 library for estimating equity and expected value in Texas hold 'em using Monte Carlo simulation.

Usage

Tell monty your hole cards, the community cards, and the number of players including yourself:

var monty = Monty.pocket(EIGHT.of(CLUBS), NINE.of(CLUBS))
                 .flop(SEVEN.of(CLUBS), TEN.of(CLUBS), ACE.of(HEARTS))
                 .players(4);

Get a lazy, infinite, parallel stream that pseudorandomly samples the possible outcomes given those constraints, running independent simulations on every thread made available to it:

IntStream outcomes = monty.stream();

An outcome is represented by a nonnegative integer indicating the number of players that you split the pot with, including yourself: 0 means you lost, 1 means you won, and n > 1 means an n-way tie. Or monty can run a given number of trials and summarize the outcomes for you:

var showdown = monty.limit(1_000_000);

Your equity is the fraction of the pot that you won on average across every simulated outcome, which converges to the true average across every possible outcome:

assert Math.abs(showdown.equity() - 0.5228d) < 0.001d;

The expected value of a call is the ratio of your estimated winnings to the size of the raise:

var pot = 100;
var raise = 50;

assert showdown.expectedValue(pot, raise) > 1.0d;

The increase in precision obtained by further trials is subject to diminishing returns.