Warning in NUTS sampler for _epsilon_bar

[nabriis]

Description
The line of code, below, in NUTS is repeated twice and it generates a warning, we want to fix the line to get rid of the warning.

if self._epsilon_bar == "unset": # Initial value of epsilon_bar for sampling

The warning:

/Users/amal/Documents/research_code/CUQI-DTU/CUQIpy/cuqi/experimental/mcmc/_hmc.py:315: FutureWarning: elementwise comparison failed; returning scalar instead, but in the future will perform elementwise comparison
  if self._epsilon_bar == "unset": # Initial value of epsilon_bar for sampling

Example to reproduce

See FENIcs notebook in CUQI book.
https://github.com/CUQI-DTU/CUQI-Book/pull/74/files#diff-65b82e897cf4d25e53f93d35bcc5f582f2a6ebc08a631af478f5546e7e591fd5

Related online discussion of this warning
https://stackoverflow.com/questions/40659212/futurewarning-elementwise-comparison-failed-returning-scalar-but-in-the-futur

DoD

• Fix to get rid of the warning is implemented
• Fix is reviewed and merged
• Issue created for CUQI-Book to rerun the notebooks that display this warning

[amal-ghamdi]

Can you please review the DoD @jakobsj? Thanks!

[jakobsj]

DoD approved @amal-ghamdi