 leapfrog step, the negative log probability function and its
gradient need to be evaluated at the position corresponding to the
current parameter values (a more detailed sketch is provided in the
next section). These are used to update the momentum based on the
gradient and the position based on the momentum.</p>
<p>For simple models, only a few leapfrog steps with large step sizes are
needed. For models with complex posterior geometries, many small
leapfrog steps may be needed to accurately model the path