An fast realtime interactive fractal zoomer
3.4.6 Calculation of the Mandelbrot Set
Internal Mandelbrot caluclation loop is unrolled -- it calculates
first 8 iterations using normal method and then it expects that number
of iterations will be probably large so it switches into mode, where it
calcualtes iteratins in block of 8 with one bailout test at the end.
When bailout is received, saved values from previous iterations is
restored and last 8 iterations are recalcualted slowly to get exact
values. This leps a lot especially at pentium, where conditionals in
floating point code is slow.
Another stuff is periodicity checking. XaoS has both version of loops ---
with ans without periodicity checks. In most cases it uses nonperiodicity
checking version. Periodicity check version is used just in case, some inside
set pixel has beed found during solid guessing paste around. This is done
mainly because periodicity checking verson of loop is significnatly slower.