Further parameters for the initial guess

The initial guess can be furthermore controlled by some parameters which are set to "no" by default.

• ahfinder::ahf_guessold (steerable)
  To use on old horizon as initial guess set ahf_guessold = "yes". However, if during the evolution the apparent horizon jumps discontinuously it might be lost by using this option.
• ahfinder::ahf_nn0, ahfinder::ahf_nn2
  If no old horizon is used the inital guess can be specified further for the minimization algorithm. This algorithm is sensitive to the initial guess, so this is important. The initial guess is set up by an expansion in spherical harmonics in the first two coefficients (l=0,l=2). The default for both these parameters are 10, in which case the algorithm tests 100 different combinations to find the best initial guess.
• ahfinder::ahf_sloppyguess
  It is also possible to use only a sphere as initial guess. This is much faster and is done by using ahf_sloppyguess = "yes". In this case a number of spheres (specified by ahf_nn0) with different radii are tested for the initial guess.
• ahfinder::ahf_inner
  If one wants to look for an inner horizon instead of an outer one, use ahfinder::ahf_inner = "yes". This only works with the minimization algorithm.