Author: J. Wesley Cleveland
Date: 15:05:15 06/20/02
Go up one level in this thread
On June 20, 2002 at 16:05:26, Robert Hyatt wrote: >On June 20, 2002 at 14:38:55, Robert Henry Durrett wrote: > >>On June 20, 2002 at 13:03:10, Robert Hyatt wrote: >> >>>On June 20, 2002 at 12:30:47, Keith Evans wrote: >>> >>>>On June 19, 2002 at 23:27:51, Robert Hyatt wrote: >>>> >>>>>On June 19, 2002 at 20:45:33, Keith Evans wrote: >>>>> >>>>>>On June 19, 2002 at 14:33:56, Tom Kerrigan wrote: >>>>>> >>>>>>>On June 19, 2002 at 13:10:42, Robert Hyatt wrote: >>>>>>> >>>>>>>>I don't care about the 32 bit specint. I care about the fact that a >>>>>>>>1.4ghz pentium runs Crafty at about 750K nodes per second. The 600mhz >>>>>>>>21264 ran it at over 800K. And 600mhz is _not_ the fastest 21264 around. >>>>>>>> >>>>>>>>The 1ghz mckinley runs it twice as fast as that 1.4ghz pentium, 1.5M nodes >>>>>>>>per second. _that_ is definitely "something to get excited about" IMHO.. >>>>>>> >>>>>>>So you like the 21264 and the McKinley. That's great. Maybe you can start a fan >>>>>>>club, instead of posting to a thread where people are trying to have an >>>>>>>intelligent conversation about 64-bit computing. >>>>>>> >>>>>>>-Tom >>>>>> >>>>>>Is there an easy way to compare a 1.4 GHz P3 to a 1 GHz McKinley and see where >>>>>>this Crafty performance increase is coming from? I'm not at all familiar with >>>>>>McKinley, but would it be possible to run a version of Crafty compiled for >>>>>>32-bits on a McKinley and compare that to a Crafty compiled for 64-bits on >>>>>>McKinley? Is this a dumb idea? If this isn't possible, then it's going to be >>>>>>difficult to tell where the performance gain is really coming from. >>>>>> >>>>>>-Keith >>>>> >>>>>I don't know that you could do this. It would require that the compiler know >>>>>how to implement 64 bit ints as 2x32 bits, which on a mckinley would be a waste >>>>>of the compiler-writer's time... >>>> >>>>So what's wrong with Tom's suggestion - "You can make a bitboard class that >>>>contains two 32-bit ints and overload all the int operators and run it on a >>>>64-bit chip. ... renaming his source files from .c to .cpp and writing this >>>>simple class" >>>> >>>>Is this is a valid experiment then why not do it and settle the argument? >>>>Someone might even consider publishing a paper on it. (Maybe Tom would volunteer >>>>to hack the code if you don't want to bother?) If it's not valid then what's >>>>wrong with it? Do you think that the compiler would outsmart Tom and use 64-bit >>>>words for the bitboards anyways? >>>> >>>>What would your prediction for such an experiment be? That the version with 2 x >>>>32-bit bitboards would run half as fast as the version with 64-bit bitboards? >>>> >>>>I'm pretty sure that we could find some willing volunteers to run some simple >>>>experiments on their hardware. >>>> >>>>-Keith >>> >>> >>>It could certainly be done. However, I don't see what it would prove. >>>Other than that 64 bit operations are more efficient when done in one >>>"chunk" than in two. That seems intuitive anyway. It would also present >>>a few problems, with the FirstOne() and LastOne() PopCnt() functions that >>>use assembly on the PC but not on the 64 bit machines (yet). >>> >>>Remember that my comparison results are for the "best" 32 bit crafty I have >>>vs the 64 bit machines. Unfortunately, the 64 bit machines have no assembly >>>so they are at a significant disadvantage to start with, yet they are >>>blazingly fast. When I have access to one for a period of time, that >>>advantage will go away completely. Then it will be 32 vs 64 in a _real_ >>>comparison, not a biased-toward-32-bit mode as it is done today. >> >>Bob H., as an "outsider" to "the world of professional software design," I don't >>know how to ask this using the "insider" terminology. Here is my question >>anyway: Does your 64-bit Crafty fully utilize all of the capability that >>"64-bit" has to offer? In other words, does it represent the ultimate >>performance one might get by using "64 bit," whatever that is? > >No. The 32 bit version has some assembly for important things like >finding the first 1 bit, etc. The 64 bit versions have used plain >software implementations of those functions. The same you would get >if you compile Crafty without any of the .asm stuff included. > >> I repeat: Do >>you fully utilize all that "64 bit" has to offer in your engine? Part of the >>question is whether or not there exist suitable compilers. > > >To make the test fair, 64 bit versions of the 32 bit assembly need to be >done. That won't happen until the processors are available of course. Then >the speed gain will be more significant. > It would be a lot simpler and equally fair to compile a 32 bit version of crafty without assembler.
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