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function composition and short-lived objects
f#functional

I'm trying to write a set of functions that can be used as arguments to some other functions.

Here is a cooked example of what I'm trying to do:

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let pass1 x = Vector.init 1 (fun _ -> Seq.hd x)

let pass2 (v:vector) = v.[0]

let use1 xForm = 


     let first = Vector.zero 1

     first |> xForm

let use2 xForm = 


     let first = seq{ 0 }

     first |> xForm

use1 pass2

use2 (pass1 >> pass2)

My problem is that (pass1 >> pass2) will be called quite a lot. So, I really need to avoid the unneeded vector allocation. Is there a way to keep the functional niceness while avoiding allocations.

.

I doubt it, but hopefully someone cleverer than me will suggest something.

By on 3/18/2009 9:27 AM ()

I changed it to use Seq, and it is much faster. I went from about 40-50% to 80-90% utilization on my quad core.

Also, I tried inputing a temp vector in the parent scope. but, that didn't improve things. I think the problem was more to do with vector than the alloc. But, I'm not sure. This code improved things. But, not as much as I expected.

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let pass1 (v:vector) x = Vector.inplace_mapi (fun _ -> Seq.hd x) v

v

Is Seq is the ideal container for ``forrested'' maps? In what cases should I convert to LazyList?

By on 3/18/2009 9:44 AM ()

Try it and measure.

By on 3/18/2009 10:05 AM ()

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