Author: martin fierz
Date: 11:17:08 04/10/04
Go up one level in this thread
On April 10, 2004 at 13:36:50, Anthony Cozzie wrote:
>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]];
i still don't understand: how does the compiler know what values table[value]
can take? in your example, the compiler knows from somewhere that these values
are in the range 0...X. how?
cheers
martin
>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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