why scientific programming does not compute

There are terrifying statistics showing that almost all of what scientists know about coding is self-taught,” says Wilson. “They just don’t know how bad they are.” As a result, codes may be riddled with tiny errors that do not cause the program to break down, but may drastically change the scientific results that it spits out.

full article

http://www.nature.com/news/2010/101013/full/467775a.html