Thursday, November 26, 2009

Code dojo

I attended code dojo in Oslo today. This was my seconds dojo and a fun experience. We worked in four groups, two python, one java and one C#.

The task at hand was to create a scoring program for tennis. Simple enough to do in 2 hours, yet complex enough to spike good discussions. And it was interesting to see how some did top-down design and others bottom-up.

Coding in groups TDD style is a great experience which I recommend for anyone who haven’t tried it. The group dynamic is very different from coding by yourself and it broadens your problem solving skills.

Looking forward to the next dojo!

Wednesday, November 18, 2009

Upgrade from 32bit Office 2007 to 64bit Office 2010

I downloaded the beta of Office 2010, but wanted to go with the 64bit version, since one exists. 64bit Windows 7 deserves a 64bit Office.

My main concern since an upgrade is not possible from 32bit to 64bit was that my Outlook account wouldn’t be kept. To make sure I had a backup of it I exported the profile from registry:

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Outlook

I didn’t bother backing up any files, since everything is on the Exchange server.

My next step was to uninstall Office 2007, did a reboot, and started Office 2010 installations. Did a reboot, started Outlook and it all worked. The registry key had not been removed upon uninstalling 2007, so Outlook 2010 detected the profile and used it without any work on my part.

Conclusion is that you can just uninstall 2007 and install 2010 and keep your Outlook settings. But it never hurts to backup your outlook registry key just to be sure.

I had trouble activating but found a solution at

Thursday, November 12, 2009

Disk based data structures

codeplex-logo Last year I created a project where I used memory mapped files as storage for a large Array. I’ve now polished the project a bit and included generic List and Dictionary implementations as well. The project can be found at Disk Based Data Structures - CodePlex.

I’ve also created a serializer project which benchmarks and picks the fastest serializer method for your type. This serializer is used to persist the data to disk. The classes are also implemented thread safe.

Background for the project

A disk based version of an array would require a lot of caching logic to make it perform fast enough compared to a pure memory implementation and a couple of years ago I stumbled across Memory Mapped Files which has long existed in the operating systems and is typically used in OS’ for the swap space.

The first time I worked with Memory Mapped files I used a library from MetalWrench, but this time around I got hold of Winterdom's much nicer implementation of the Win32 API. I've included the patch from Steve Simpson, but removed the dynamic paging since it slows things down and it's not necessary on 64bit systems. (If you want to use arrays which hold over 2gb of data on 32bit systems I recommend reverting to Steve's original version and set a view size of 200-500mb.) Future releases will use .Net 4.0’s System.IO.MemoryMappedFiles namespace.

The beauty of 64bit is that you have virtually unlimited address space, so each thread can get it's own view of the mapped file without running out of address space. 32bit Windows can only address 4gb.

As for performance my theory is that Microsoft has implemented a fairly good caching algorithm for it's swap file, so it should prove good enough for me. A few tests show a much better disk IO with the Memory Mapped API than using .Net's file IO library. I haven't testet the performance if you add the SEC_LARGE_PAGES flag, but it might help some.

Hope this library is useful for someone out there :)