Tag Archives: float

Please Calculate This Circle’s Circumference

Posted on June 26, 2014 by brucedawson

“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 const, constexpr, float, pi | 75 Comments

Float Precision Revisited: Nine Digit Float Portability

Posted on February 7, 2013 by brucedawson

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 | 17 Comments

Doubles are not floats, so don’t compare them

Posted on June 26, 2012 by brucedawson

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 | 24 Comments

Exceptional Floating Point

Posted on April 21, 2012 by brucedawson

Floating-point 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 | 24 Comments

Floating-point complexities

Posted on April 5, 2012 by brucedawson

Binary floating-point math is complex and subtle. I’ve collected here a few of my favorite oddball facts about IEEE floating-point math, based on the articles so far in my floating-point series. The focus in this list is on float but … Continue reading →

Posted in AltDevBlogADay, Floating Point, Programming | Tagged comparing, denormal, digits, float, floating point, floating point precision, floating point tricks, precision, printing | 15 Comments

Intermediate Floating-Point Precision

Posted on March 21, 2012 by brucedawson

Riddle me this Batman: how much precision are these calculations evaluated at? If you answered ‘double’ and ‘float’ then you score one point for youthful idealism, but zero points for correctness. The correct answer, for zero-idealism points and forty two … Continue reading →

Posted in AltDevBlogADay, Floating Point, Programming, Visual Studio | Tagged double, float, floating point, floating point precision, intermediate precision, precision | 43 Comments

C++ 11 std::async for Fast Float Format Finding

Posted on March 11, 2012 by brucedawson

After a recent post on float precision there was some debate about round-tripping of floats. My claim was that if you print a float with printf(“%1.8e”, f); and then scan it back in then you are guaranteed to get back … Continue reading →

Posted in Floating Point, Programming, Visual Studio | Tagged float, precision, print, scanf | 24 Comments

Float Precision–From Zero to 100+ Digits

Posted on March 8, 2012 by brucedawson

How much precision does a float have? It depends on the float, and it depends on what you mean by precision. Typical reasonable answers range from 6-9 decimal digits, but it turns out that you can make a case for … Continue reading →

Posted in AltDevBlogADay, Floating Point, Programming | Tagged double, float, floating point, floating point precision, precision, significant figures | 52 Comments

Comparing Floating Point Numbers, 2012 Edition

Posted on February 25, 2012 by brucedawson

This post is a more carefully thought out and peer reviewed version of a floating-point comparison article I wrote many years ago. This one gives solid advice and some surprising observations about the tricky subject of comparing floating-point numbers. A … Continue reading →

Posted in AltDevBlogADay, Floating Point, Programming | Tagged comparing floats, double, epsilon, float, floating point precision, floating point tricks, precision | 181 Comments

Don’t Store That in a Float

Posted on February 13, 2012 by brucedawson

I promised in my last post to show an example of the importance of knowing how much precision a float has at a particular value. Here goes. As a general rule this type of data should never be stored in … Continue reading →

Posted in AltDevBlogADay, Floating Point, Programming | Tagged double, float, floating point, game time, microseconds, precision, time resolution | 27 Comments