Author: Anthony Cozzie
Date: 10:36:50 04/10/04
Go up one level in this thread
On April 10, 2004 at 12:51:28, martin fierz wrote:
>hi ed,
>
>you posted the stuff below a day or two ago, and i have a question about it:
>
>you suggest creating a "translation table" to get an unbroken and continuous
>string of characters and then use this in a switch statement. if i understand
>this right, i'd have to make a rather large first table which does something
>like
>
>material-signature = function(pieces); somewhere in the 0...~4000 range (as far
>as i can see, you need to be able to represent any combination of 1 vs 1 or
>better 2 vs 2 pieces)
>
>X=conversiontable[material-signature] ~ somewhere in the 0...20 range for all
>special cases you want to consider.
>
>then you do switch(X) - now how does the compiler know that the conversiontable
>values are in a single range?? i don't understand how it can possibly know this
>:-(
>
>cheers
> martin
By default it simply bounds checks.
e.g.:
if(value < 0) jmp default;
if(value > X) jmp default;
jmp[table[value]];
Or, you could always do the bounds check yourself (I think the compiler
is smart about this):
switch(a & 1023)
{
}
Lastly, I believe there is a #pragma for most compilers that removes the bounds
check.
anthony
>*******************************************************************************
>I think I misread, I thought one of your worry was all the time-consuming
>compares and jumps to go to the relevant parts of eval depending of the material
>on the board. If so, create a 2-dimensional translation table that converts the
>present material to an unbroken and continuous string of characters
>(0,1,2,3,4,5.....) and then use the result with switch-case.
>
>I have such an endgame table with over 30 entries (KPK, KRK, KBNK, KQKR, KNKPP,
>KBKPPP, KRPKR etc.) and instead of doing 30 expensive compares I just have to do
>2 initialization instructions, get the value of the translation table and then
>the switch-case will move me with just one assembler instruction to the right
>place (label). Imagine the speed gain.
>
> switch (val) { case 0 : goto KPK;
> case 1 : goto KRK;
> case 2 : goto KNBK;
> case 3 : goto KQKR;
> ...................
> case 99 : goto whatever;
> }
>
>Again, the compiler will translate this to just *one* instruction, even if you
>have 200 entries and thus save 200 compares.
>
>Ed
>*****************************************************************************
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