From my experience with some programs I am developing in C, I think the cause of this kind of error might be a variable that got an inf, -inf or nan value (IEEE specifications for floating numbers). Once a variable has got such a value, no operation (addition, multiplication, etc.) will change it, and this will be transmitted to other variables. Of course, this does not explain how this happened in the first place. What I don't know is what happens if you run fractint using exactly the same parameters once more. In case the symptom appears in a haphazard way, it might indicate an uninitialized variable is taking values left in the memory by other programs. Regards. ----- Original Message ----- From: Lee H. Skinner <skinner@thuntek.net> To: Fractint and General Fractals Discussion <fractint@mailman.xmission.com> Sent: Tuesday, May 20, 2003 1:55 AM Subject: Re: [Fractint] Multifractal
Ricardo M. Forno wrote:
Hi! I'm curious. How do you know that a pixel is "buggy"? Is this seen by looking at the screen, and if so, what are the symptoms? Does it happen with formulas other than Niekamp's? What is the cause of it? TIA. <<
After the showdot hits a buggy pixel, every pixel after that is colored the same. And the showdot usually slows down as if every pixel had the value maxiter. And it continues if you change passes or resolutions! You have to exit fractint and then restart it. I've not seen it in other than the multifractal formula. I'm told it only happens at 1600x1200. So far, no one knows the cause.
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