Author: Alessandro Scotti
Date: 03:05:57 08/10/04
Go up one level in this thread
On August 10, 2004 at 05:27:54, Uri Blass wrote:
>some reasons:
>1)I understand that I need to get rid of them if I want to have an SMP version
>in the future.
>
>2)Speed.
>I believe that remembering a lot of global varaibles is not the fastest way for
>chess programs and it is better to remember a varaible only when you need it
>becaause there is limited space in the fast memory.
>
>3)Clarity
>It is better to have all the time related information in one place in the
>program and when I use it in many different places understanding what is going
>on is harder.
>
>4)Bugs
>With a lot of global varaibles I may do a mistake and change a global varaible
>that I do not mean to change(espacially when there are varaibles with different
>names).
>Without global varaible if I need to call a special class the risk for a mistake
>is smaller.
>
>Uri
Ok I start to understant better now! :-)
1) I haven't experience with SMP but in general the approach I prefer is to
study a problem and develop at least a tentative design before writing code.
Otherwise, there is the risk of doing work that one think *could* be useful but
eventually isn't.
2) I'm not sure you're going to gain speed by eliminating globals, and actually
you could possibly lose some by moving them to an object because sometimes the
extra indirection may cost a bit. But it's not at all easy to predict how these
modern processors behave, I have found some really counter-intuitive cases on
occasion.
3) A really good point and I like to keep my stuff well organized too. For this,
I find the "static" keyword very handy, for example:
struct Score {
static int bishopValue;
};
It behaves like a global (there is no need to have an instance of Score) but I
find it more readable and less error prone as code must then explicitly state
where the variable comes from:
if( material >= Score::bishopValue ) ...
If needed (say, when done with experiments) static variables can also be
replaced with compile time constants by declaring them with enum inside the
class: that could speed up things a little.
4) I think this is partially addressed by 3, but of course programming with all
those globals (whether wrapped in some class or not) definitely requires special
care...
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