Margus Ramst schrieb in Nachricht <36DFC21D.23FAFB0B@peak.edu.ee>...
>Damn. I was convinced that #swich is faster and used it whenever I
>could. It is faster in BASIC, if I'm not mistaken (or am I wrong there,
>too?)

I'm not sure switch () is generally slower in C (don't know about POV-Ray or
BASIC) at all. Good optimizers will code a range of consecutive values (e.g.
4, 5, 6, 7, and 8) as a calculated jump or a jump table. But if the values
are not arranged so well, you will have code similar to the if ()
statements. In fact a switch statments should at least be converted to
something like:

if (value == value1) dothis;
else if (value == value2) dothat;
else if (value == value3) .... etc.etc.
..
else dothedefault;

The speed increase should come from the fact, that "value" doesn't have to
be reloaded, but can be compared against an array of values and according
jumps to code. Now C could be a bit difficult from my favourite language,
Pascal, in that code can fall through (if there's not break) to the next
case statement, but I'm not sure this will really slow things down. The
break statement should just be translated into a jump to the end of the
switch.

Now the implementation of #switch in POV-Ray could be different, because
POV-Ray is really interpreted, so pre-calucalted jumps or jump tables etc,
are out of the question here.

--
Rudy Velthuis

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