gegl:maze processes multiple times the whole input
It is possible to speed up gegl:maze by implementing get_cached_region virtual function to exploit the fact that the algorithms used must process the whole input at once.
PS: 'depth_first{,_tileable}' use recursion, easily producing stack overflows. With the above speed-up I think it becomes feasible to transform the algorithms in their iterative form using a GArray instead of the stack.
This operation is used in GIMP's Filters->Render->Circuit... which is reportedly crash on big images See for instance gimp#1313 (closed) and gimp#1568 (closed)