Setting up a dual boot Mac and Ubuntu requires using GPT for the Mac and MBR for Ubuntu. rEFIt is commonly used to sync these. The Ubuntu bootloader should be written to the first Ubuntu partition but occasionally it can get written to the MBR. In my case it appeared in both the MBR and the Ubuntu partition rendering Ubuntu unbootable. So how can this be fixed? Start with backing up everything just in case. If you have one hard disk the following is the command to use to remove the bootloader from the MBR:

Using version control during software development allows experimentation without worrying about removing the experimental work when it does not pan out. Apple has gone a long way to integrating Subversion into Xcode but their instructions are oriented more towards groups of developers rather than a stand-alone version control for a single developer. There is a much easier and more secure way to use Subversion.

This serial routine computes the QR decomposition of a matrix A in Re^mxn, m > = n, such that