Wednesday, 27 April 2011

Completion tasks - the easy way

One of the good things about doing things in public – people point out when you’ve missed a trick.

Just the other day, I was moaning about how Task seemed too tightly coupled to schedulers, and wouldn’t it be great if you could have a Task that just allowed you to indicate success/failure – I even went so far as to write some experimental code to do just that.

So you can predict what comes next; it already existed – I just didn’t know about it. I give you TaskCompletionSource<T>, which has SetResult(…), SetException(…) and a Task property. Everything I need (except maybe support for result-free tasks, but I can work around that).

And wouldn’t you believe it, the TPL folks shine again, easily doubling my lousy performance, and trebling (or more) the performance compared to “faking it” via RunSynchronously:

Future (uncontested): 1976ms // my offering
Task (uncontested): 4149ms // TPL Task via RunSynchronously
Source (uncontested): 765ms // via TaskCompletionSource
Future (contested): 5608ms
Task (contested): 6982ms
Source (contested): 2389ms

I am hugely indebted to Sam Jack, who corrected me via a comment on the blog entry. Cheers!