Re: [Chicken-users] spectralnorm algorithm from comp. language shootout

[felix winkelmann]

On 05 Jun 2005 17:20:40 +0200, Matthias Heiler <address@hidden> wrote:
> Hi,
> 
> I played with the spectral norm algorithm from the computer language
> shootout http://tinylink.com/?fFObJZJlyQ
> 

Here a few points:

- loop is (relatively) slow - it expands into at least one call/cc for example
  (this isn't as bad as it sounds, continuations are fast with chicken, but if
  you want to squeeze out perfornance, a simple 'do' loop is faster).
- I would add `(declare (block) (disable-interrupts))'. 
- The real whopper: f64vector. Extracting doubles from a f64vector is
  really costly: we have to cons flonums all the time. Putting the flonums
  into a vector instead reduces the need to create flonums (there are already
  consed and pointers to them are stored in the vector). This doesn't
  work with the FFI-wrapped code, of course, which wants f64vectors.

Attached an altenative version, here the Scheme code needs about
7 seconds (compared to 13 seconds for the original version).


cheers,
felix

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