Re: The old college try

On 30/05/2025 10:56, vallor wrote:

In the case I gave it, O(n) becomes O(1).  It was
a "trick" I figured out on the Commodore PET in
the 80's:  using the numeric keypad as an index
for arrays to add x/y values to compute a player's
movement in a rudimentary game I wrote.  (In BASIC,
I'm ashamed to say. ;)  The array computation replaced
a bunch of if-then statements, and it ran a lot faster
after that.

The time: 1989.
The date: Atari ST.
The program: ballistics.
Potential problem: trig functions are slow, right?
The optimisation: pre-calculate sine, cosine, and tangent lookup tables at the start of the program.
The result: slow to initialise, but acceptable speed thereafter.
The upgrade: remove the lookup table calcs and just call sin, cos etc when needed.
The result: blitzingly fast.
The lesson: premature optimisation is the root of all evil.
--
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
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