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Category Archives: Floating Point
Please Calculate This Circle’s Circumference
“Please write a C++ function that takes a circle’s diameter as a float and returns the circumference as a float.” It sounds like the sort of question you might get in the first week of a C++ programming class. And … Continue reading
There are Only Four Billion Floats–So Test Them All!
A few months ago I saw a blog post touting fancy new SSE3 functions for implementing vector floor, ceil, and round functions. There was the inevitable proud proclaiming of impressive performance and correctness. However the ceil function gave the wrong … Continue reading
FloatingPoint Determinism
Is IEEE floatingpoint math deterministic? Will you always get the same results from the same inputs? The answer is an unequivocal “yes”. Unfortunately the answer is also an unequivocal “no”. I’m afraid you will need to clarify your question. My … Continue reading
Float Precision Revisited: Nine Digit Float Portability
Last year I pointed out that float variables can be converted to text and then back to the same binary value using printf(“%1.8e”). You can also use %.9g for more compact results. I also supplied a test program that used … Continue reading
Posted in Floating Point
Tagged float, floating point, floating point precision, printf, scanf
13 Comments
Game Developer Magazine Floating Point
This is for references, code examples, and discussion regarding the floatingpoint article in the October 2012 Game Developer Magazine.
Doubles are not floats, so don’t compare them
I’ve seen a few online discussions linking to my Comparing Floating Point Numbers page for misguided reasons and I wanted to discuss those reasons to help people understand why throwing epsilons at the problem without understanding the situation is a … Continue reading
Posted in Floating Point, Programming
Tagged base conversion, epsilon, float, floating point, precision
17 Comments
FloatingPoint Poetry
I gave a talk at iFest on Saturday that briefly covered some performance and precision issues taken from my series of floatingpoint blog posts. My talk was after Ed Fries, who did a brilliant talk on art and constraints, centered … Continue reading
That’s Not Normal–the Performance of Odd Floats
Denormals, NaNs, and infinities round out the set of standard floatingpoint values, and these important values can sometimes cause performance problems. The good news is, it’s getting better, and there are diagnostics you can use to watch for problems. In … Continue reading
Posted in AltDevBlogADay, Floating Point, Performance, Programming
Tagged denormal, floating point, infinity, NaN, special numbers, specials
10 Comments
Exceptional Floating Point
Floatingpoint math has an answer for everything, but sometimes that’s not what you want. Sometimes instead of getting an answer to the question sqrt(1.0) (it’s NaN) it’s better to know that your software is asking imaginary questions. The IEEE standard … Continue reading
Posted in AltDevBlogADay, Floating Point, Programming
Tagged divide by zero, double, exceptions, float, floating point
20 Comments