monty

monty is a Java 23 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:

Monty 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:

Showdown showdown = monty.limit(1_000_000);

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

assert Math.abs(0.523d - showdown.equity()) < 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;

Accuracy tends to increase with further trials, subject to diminishing returns.