"Richard Heathfield" <rjh@see.sig.invalid> wrote in message
> Malcolm McLean said:
>
> <snip>
>
>> if we're not doubling speed at least we aren't really speeding things up.
>
> Wrong. I can cite a 20% reduction in run-time in a (fairly hefty) program
> that had taken 25 seconds to produce one particular kind of quotation.
>
Another case is interactive graphics. It doesn't matter how long your
calculation takes as long as you make the next frame. If you miss it by a
few microseconds, you've got all of 17 millseconds to play with until the
next one come along.

However generally I regard a 100% speedup as about the threshold for code
worth my time optimising.

--
Free games and programming goodies.
http://www.personal.leeds.ac.uk/~bgy1mm