I don't know, from this I can't really see the memory cost or GC impact. And the parallel statement doesn't tell me anything of the threading model. I know that

I don't know, from this I can't really see the memory cost or GC impact. And the parallel statement doesn't tell me anything of the threading model. I know that I see a lot of intermediate states being created which is not so good. If this code were shown to compile to the imperative equivalent though, I'd definitely think about learning F#.