Release 20.11

• The minimum C++ standard supported by Castro is now C++14. Most modern compilers
  support C++14; the notable exception is RHEL 7 and its derivatives like CentOS 7,
  where the default compiler is gcc 4.8. In that case a newer compiler must be loaded,
  particularly a version of gcc >= 5.0, for example by installing devtoolset-7 or (if
  running on an HPC cluster that provides modules) using a more recent gcc module. (#1284)

• A new option, castro.retry_small_density_cutoff, has been added. In some
  cases a small or negative density retry may be triggered on an update that
  moves a zone already close to small_dens just below it. This is not uncommon
  for "ambient"/"fluff" material outside a star. Since these zones are not
  dynamically important anyway, triggering a retry is unnecessary (and possibly
  counterproductive, since it may require a very small timestep to avoid). By
  setting this cutoff value appropriately, the retry will be skipped if the
  density of the zone prior to the update was below the cutoff. (#1273)