Category Archives: Floating Point

Intel Underestimates Error Bounds by 1.3 quintillion

Intel’s manuals for their x86/x64 processor clearly state that the fsin instruction (calculating the trigonometric sine) has a maximum error, in round-to-nearest mode, of one unit in the last place. This is not true. It’s not even close. The worst-case … Continue reading

Posted in Floating Point, Investigative Reporting, Programming | Tagged , , | 96 Comments

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

Posted in Floating Point, Programming | Tagged , , , | 57 Comments

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

Posted in Floating Point | Tagged , | 27 Comments

Floating-Point Determinism

Is IEEE floating-point 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

Posted in Floating Point, Visual Studio | Tagged | 47 Comments

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 , , , , | 13 Comments

Top Eight Entertaining Blog Facts for 2012

The end of the year is a traditional time for lists and I thought I’d do a post just to summarize the most interesting or surprising things that I discovered while writing this blog during 2012.

Posted in Bugs, Floating Point, Performance, Programming | Tagged , , , | 1 Comment

Game Developer Magazine Floating Point

This is for references, code examples, and discussion regarding the floating-point article in the October 2012 Game Developer Magazine.

Posted in Floating Point | Tagged | 3 Comments