[plt-scheme] ->d Performance

Here is a graphical example where you can see the difference in speed.

The life-bitblt-slower.ss requires matrix-slower.ss (with ->d and no bounds
checking in the body of the code) and is really slow.

The life-bitblt-faster.ss requires matrix-faster.ss (with -> and bounds
checking in the body of the code) and performs okay.

Other than the contract and the corresponding presence or ansence of bounds
checking (to give the same functionality), the code is identical. [The only
difference between life-bitblt-slower.ss and life-bitblt-faster.ss is the
require statement.]

They all do better compiled. But it interesting to see the speed difference.

Note that the code used the science and animated-canvas collections from
PLaneT and will download them the first time any of them are run, which
takes some time.

I sent a response that also includes a version that doesn't use the matrix
abstraction at all (and therefore no contracts) that is much faster that the
'faster' version here. You'll get it when/if the moderator releases it.

Doug

On Sat, Apr 11, 2009 at 1:55 PM, Robby Findler
<robby at eecs.northwestern.edu>wrote:

> ->d actually evaluates the expressions (and/c
> exact-nonnegative-integer? (</c (matrix-rows matrix))) each time you
> call the function, and that evaluation involves building up a contract
> combinator (and doing various error checking) before actually checking
> the contract. That's where the extra overhead comes from. In
> comparison with the -> contract, all of that work is done once, before
> the contract is even attached to the value. I have experimented with
> various optimizations to avoid this work, but there is a lot to do to
> make that happen.
>
> Robby
>
>
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