Comments on: Challenge #1: How Small Things Have Big Impact

By: Damion

Damion — Thu, 30 Mar 2006 06:52:02 +0000

Not quite the same, but they once had a bug on Ultima Online where the programmers accidentally redefined TRUE = 0. You wouldn’t believe the stuff that breaks.

By: Justin

Justin — Mon, 27 Mar 2006 19:36:27 +0000

I realize I’m late for not reading feeds over the weekend, but…

When i first saw this (though now i see above that it was a printing error more than a comparison error) I immediately thought of having it pounded into me from a young age never to compare foating point numbers directly in C.. so I’d always do:

#define EPSILON 0.0000001 // adjust for accuracy

if( fabs( a – b )

By: Captain P

Captain P — Sun, 26 Mar 2006 20:29:04 +0000

As we always say: 1 + 1 = 3 for large values of 1. :)

I went for the string/float solution. I’d reason that 70.492 would be printed as such. But not in php I understand? Odd…

By: Tim Fisher

Tim Fisher — Sun, 26 Mar 2006 10:20:38 +0000

It was actually just a debug issue, the debugger was always rounding up! The data types were both doubles.

By: Duncan

Duncan — Sun, 26 Mar 2006 04:43:59 +0000

I’ve noticed that even with identical types, sometimes the process of getting to the desired values can result in a minor discrepancy. For example (in C/C++) if both values were floats, but the incremental process to get the values is different, the data in memory can still be different. One can be 70.49 and the other might wind up 70.899999999999. I was always taught that when using floating point variables in comparisons to avoid direct equates at all cost. Always make it a range, or a = comparison.

By: John H Scott

John H Scott — Sat, 25 Mar 2006 21:37:56 +0000

Using the “==” operator does not always compare the value of two objects, but whether or not the two objects are the same peice of data. This could very well be the case in the example given.

By: Alexei A. Korolev

Alexei A. Korolev — Sat, 25 Mar 2006 18:04:10 +0000

I got similar error when did BSP subdivision :)

By: Thomas White

Thomas White — Sat, 25 Mar 2006 15:25:54 +0000

I’ve had this problem once before, but luckily Visual Studio has an ASP.NET debugger ;)

By: Tim Fisher

Tim Fisher — Sat, 25 Mar 2006 10:30:21 +0000

I know I’m not allowed BUT, it was PHP. When you debug it seems to round everything to 2 decimal places!!!

By: Juuso - Game Producer

Juuso - Game Producer — Sat, 25 Mar 2006 08:24:34 +0000

@KGodwin: no no no, I won’t. You gotta think harder ;)
(or read the solution from other posts ;)

@Ben: yeh, I noticed your post after sending mine :)