Author: Vincent Diepeveen
Date: 17:59:49 06/06/02
Go up one level in this thread
On June 06, 2002 at 20:33:02, Robert Hyatt wrote: >On June 06, 2002 at 19:54:24, Vincent Diepeveen wrote: > >>On June 06, 2002 at 10:24:27, Robert Hyatt wrote: >> >>There is a huge difference between the test on this >>processor, because running at 2 processors it was very >>slow from hardware viewpoint. Like 1.5 was mentionned >>then too. > >OK... so what? It was very fast on the single-cpu test... >> >>Also we talk about a very old version of crafty here compared >>to the crafty that's existing today. I remember that you had >>way less king safety and some other scans in these crafties >>and you did do less here and there. > > >it was the last 16.x version I believe. I am now on 18.15, but >king safety hasn't been greatly modified during that span... You have a big number of functions called 'evaluationBLABLA' where blabla stands for a lot of simplistic things. The evaluation itself eats just 10%, so obviously that other 30% you lose *somewhere* in these functions. We talk about crafty from a bunch of years ago now. > > > >> >>In short about all was allowed to get more nps, whereas >>right now the 'default' assembly used for K7/P4 is fucking >>slow beginners assembly. This was of course not put to >>'slow' at this alpha test, as there were no 'specint' >>limits. > >I don't know what you mean. I know for 100% certainty that Tim didn't >modify the source code. He was running gnuchess on ICC one night and we >noticed an impossible NPS. I asked if he would try crafty and he said >sure. I sent him the source, and a we had benchmark numbers about 10 >minutes later. He then ran WAC (one minute/pos) and sent me the results >which I include here: > >1 cpu 21264/600mhz: >total positions searched.......... 300 >number right...................... 300 >number wrong...................... 0 >percentage right.................. 100 >percentage wrong.................. 0 >total nodes searched.............. 236973211.0 >average search depth.............. 4.5 >nodes per second.................. 783641 > >4 cpus quad xeon 550: > >total positions searched.......... 300 >number right...................... 299 >number wrong...................... 1 >percentage right.................. 99 >percentage wrong.................. 0 >total nodes searched.............. 280348143.0 >average search depth.............. 4.5 >nodes per second.................. 722788 > >2 cpus, 21264/600mhz: > >total positions searched.......... 300 >number right...................... 300 >number wrong...................... 0 >percentage right.................. 100 >percentage wrong.................. 0 >total nodes searched.............. 330905102.0 >average search depth.............. 4.5 >nodes per second.................. 1266767 > >Not bad. I had remembered 1M and 1.5M. I just verified that those numbers >were produced on a 667mhz machine instead, at Compaq. A slightly faster version >of Tim's machine. And right in line with the 1.5M single-cpu speed of Mckinley >at 1ghz. > > > > > >> >>It was *not* a production alpha ever, the test was done long >>before this type of alpha was put on the market, so we don't >>know whether you can buy this alpha in the shop. > >I have no idea what you are talking about. I had exactly that machine >here in my lab, for 6+ months. (single-cpu version). It ran at 667 mhz >and produced 1M nodes per second. I didn't do much with chess on it as it >was here to do some work for someone up the street from here. But it was >(and is) available for purchase. > >I had that machine over a year ago. It was not a "black box" but had a name >plate on the front and could be ordered from whomever owned the DEC stuff >at that point in time. > >Someone up in the medical school bought the thing, left it here for me to >work on some code for him, and that was that... > > > >> >>There is another list of things wrong. >> >>For example if it was such a slow processor, why only getting >>1.5 hardware speedup out of 2 processors? > >Because the hash table used locks. And the locks were very bad on the >alpha. We later went to the "lockless hash table" that I now use. I >never had access to either machine (Tim's or the one in the medical >school here) to run WAC again after that was fixed. The out-of-order >memory writes on the alpha require a "barrier" prior to clearing the >lock, and the lock/unlock themselves are also very expensive. Both >together (lock/barrier) really produced a bottleneck. No mystery at >all... > >I think we mentioned this in the paper we wrote for ICCA which ought to >appear in the next issue. > > > >> >>That means a cheap dual K7 getting 2 million nodes a second is still >>faster than this 1.5 million nodes a second dual alpha. > >I have not yet seen a dual K7 get 2M nodes per second with Crafty... > > >> >>Note that we compare a todays crafty version with that special >>old thing then. Also we assume then beginners assembly for the >>current dual K7 crafty, versus optimal defines for the alpha. > >The version Tim had was not that old. The version I ran on the 667 mhz >machine was even newer, in the 17.x group... > >> >>That's not a very fair compare. > >Seems perfectly fair to me...
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