<div class = "glossary-entry">
<h3>energy</h3>

<span class="help-block" style = "margin-top: 15px;">
  <em>Quick definition</em>
</span>
  
The <code>energy</code> is the value of the Hamiltonian (up to an additive 
constant) at each sample.

<br><br>
<h4>More details</h4>

<p>
While divergences can identify light tails and incomplete exploration of the target distribution, the energy diagnostic can identify overly heavy tails that are also challenging for sampling. Informally, the energy diagnostic for HMC quantifies the heaviness of the tails of the posterior distribution. The energy diagostic plot 
shows overlaid histograms of the (centered) marginal energy distribution
and the first-differenced distribution. Keep an eye out for 
discrepancies between these distributions.
</p>

For more details see 
<a href="https://arxiv.org/abs/1701.02434"> Betancourt, M. (2017). A conceptual introduction to Hamiltonian Monte Carlo.</a>

</div>
