Via dotNetSlackers, an all-too-familiar story: If only we'd used ANTS Profiler earlier... we would have had a shot at the $2 million cash prize!.  The familiar part is how code profiling seems to always be a last consideration for developers – not the $2M part, obviously!

Written by a member of the Princeton DARPA Grand Challenge Team (the competition where entrants build driverless vehicles that must successfully negotiate a pre-set course), the post describes how an apparent “memory leak” in their .NET code was causing their test vehicle to literally crash:

We were unique among the teams in the finals, in that we used stereo vision, as opposed to scanning lasers, to detect and range obstacles. All in all, we wrote 10,000 lines of C# code to drive the cars.

In the finals, we ran for 9 miles before succumbing to a memory leak in the obstacle-detection code. Actually, most of our code is written in garbage-collected C#, so it wasn't a memory leak per se, but it wasn't until two weeks later that we discovered the true problem.

The nature of the problem?  Objects that while “deleted”, still maintained subscriptions to events, thus causing their heap to blow chunks.  How did they figure this out?  By profiling their code to see how it was working in real-time:

One of our team members downloaded the 14-day trial of ANTS Profiler, and we ran it on our car's guidance code. We profiled the memory usage and saw the obstacle list blowing up. How could this be? We called "delete" on those old obstacles! To our amazement, it was only minutes before we realized that our list of detected obstacles was never getting garbage collected. Though we thought we had cleared all references to old entries in the list, because the objects were still registered as subscribers to an event, they were never getting deleted.

We added one line of code to remove the event subscription and, over the next three days, we successfully ran the car for 300 miles through the Mojave desert.

Definitely a testament to the power of profiling!

Personally, I prefer AQTime to ANTS as the latter in my experience doesn’t profile SharePoint applications very well – if at all.  It also has an array of reports and dashboards that I like, eg. callgraphs, top-10 hit counts, longest methods to execute (with and without children) and more.  Nonetheless, it’s well worth trying the free versions of each on your own code to see how they work and what you prefer. 

To me, profiliers are the best investment you can make in your tools, outside of an IDE and refactoring aids.