Category Archives: Computers

Mac OS X and Windows

Switching between Visual Studio .Net and Mono with MonoDevelop

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For reasons best not examined too closely I switch between between Mac and PC which, since I earn my crust largely with .Net development, means switching between Visual Studio and MS.Net and MonoDevelop with Mono.

Mono is very impressive, it is not at all a half hearted effort, and it does some stuff that MS haven’t done. But when switching environments, there’s always the occasional gotcha. Here are some that have got me, and some solutions.

Gotcha: Linq Expressions don’t work on Mono

Solution: Add a reference to System.Core to your project.

Question: What version of NUnit is built in to mono?

As of Feb 2011, it’s nunit 2.4.8.

Highly Unlikely — The Mark of the Beast Bug

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In 1991, amongst a series of theorems about rounding in floating point arithmetic calculations, the author parenthetically noted that rounding a number to 53 significant digits, and then rounding it again to 52 significant digits, might produce a different answer compared to when you do the rounding to 52 digits all in one go. He all but apologised for the parenthesis, noting it was “highly unlikely to affect any practical program adversely.”

19 years and 10 months later a researcher discovered that the “Mark of the Beast Bug” could freeze almost any computer in the world, and that millions of webservers could be taken down by it almost at the touch of a button — because of an error when rounding a very very small number, first to 53 significant digits, and then to 52.