[Haskell-cafe] Re: Parallel combinator, performance advice

You create one MVar for each task in order to ensure all the tasks are done. This is pretty heavyweight. You could create a single Control.Concurrent.QSemN to count the completed tasks, starting with 0. Each task is followed by signalQSemN with a value of 1. (I would use "finally"). As parallel_ launches the tasks it can count their number, then it would call waitQSemN for that quantity to have finished. -- Chris