Author: Robert Hyatt
Date: 08:17:50 06/24/04
Go up one level in this thread
On June 24, 2004 at 09:03:57, Gian-Carlo Pascutto wrote:
>On June 24, 2004 at 07:56:32, Anthony Cozzie wrote:
>
>>Bob's code looks like this in assembly:
>>
>>if(wtm)
>>{
>> xor eax+0x334, ebx //take memory at eax+0x334 and xor it with ebx
>> ...
>>
>>Your code would look like
>>
>> xor eax + 8*ecx + 0x334, ebx
>> ^--- Index register
>>
>>Register pressure is one of the biggest problems with bitboards on x86. Just
>>having 1 bitboard in registers requires almost 1/3 of the registers.
>
>I don't see how this is possibly a justification:
>
>1) Because of the same register pressure you're talking about, most of the
>data in x86 is retried from caches. Duplicating code is not helping
>cache pressure.
Caches are getting bigger and bigger. 1995 had 16kb as big. Today has
512-1024K as big and that can even be pushed higher if you want to pay...
>
>2) You need to handle the branch too. The cost of that is going to be way
>higher than the cost of setting up/restoring a register.
That branch is probably predicted perfectly. it is "yes" "no" "yes" "no".
something the PIV handles well although others do not.
>
>>Switch is _fast_. Again, in assembly:
>>
>> and eax, 0xF
>> jmp table[eax]
>
>An indirect jmp fast?
>
>Are you joking?
>
>Also good luck with getting the compiler to generate that code.
>
>--
>GCP
This page took 0.02 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.