# MrBayes

## Description

MrBayes is a program for Bayesian inference and model choice across a wide range of phylogenetic and evolutionary models. MrBayes uses Markov chain Monte Carlo (MCMC) methods to estimate the posterior distribution of model parameters.

In addition to the official MrBayes distribution, a modified version that uses the Gamma-Dirichlet and Inverse Gamma-Dirichlet priors for branch lengths (Rannala et al. in press; Zhang et al. 2012). This also includes the two exponential priors on internal and external branch lengths described by Yang & Rannala (2005) and Yang (2007). Please see Ziheng Yang's site for more information and citations. The modified version is only installed for openmpi and is called mb_Dirichlet. To run this version, simply replace mb with mb_Dirichlet in the examples below.

## Required Modules

### Serial

- mrbayes

### Parallel (OpenMP)

- intel
- mrbayes

### Parallel (OpenMPI)

- intel
- openmpi
- mrbayes

## System Variables

- HPC_MRBAYES_DIR - installation directory

For MPI jobs: Remember that the total number of cores cannot be greater than the total number of chains MrBayes is using. For example, if you have 2 runs, each with 4 chains, the maximum number of cores to request is 2*4=8 cores. As long as the number of cores is under 12, it is best to keep nodes=1 (nodes = physical machines) as that will keep all communication within a single node. If you need more than 12 cores, you will probably want to add :infiniband to the request. (e.g. nodes=4:ppn=8:infiniband).