Roger Alexander quoted a formula in
fractint.frm
GenInvMand_rjr { ; Jm Collard-Richard and rjr 2k03
c=z=1/pixel+p1:
z=fn1(z)*fn2(z+p2)+fn3(fn4(c))
|z|<=4
;SOURCE: fractint.frm
}
; Notice that fn3(fn4(c)) is a constant. In a
re-entrant function, constant input yields constant output,
; so the formula can be sped up quite a
bit like this:
GenInvMand_rjr { ; Jm Collard-Richard
and rjr 2k03
z=1/pixel+p1, c=fn3(fn4(z)):
z=fn1(z)*fn2(z+p2)+c
|z|<=4
;SOURCE: fractint.frm
}