slowness

[Jonathan Crook]

Hi, I have been working on a mandelbrot fractal generator, and have
decided to use GMP, to maintain precision through extensive zooming.
However, whereas a fractal would generate in <1s using long doubles,
with mpf_class it takes around 180s. I understand that in my code, this
causes an incredible amount and frequency of function calls, and thus
also GMP arithmetic, but am I to expect this kind of performance
overhead, or am I merely doing something wrong?

Thanks, Jonny.