Author: Robert Hyatt
Date: 18:51:19 02/01/05
Go up one level in this thread
On February 01, 2005 at 17:19:26, Vincent Diepeveen wrote: >On February 01, 2005 at 16:28:22, Robert Hyatt wrote: > >Still didn't read the subject title? > >[snip] > >>Because a cluster can't offer 1/100th the total memory bandwidth of a big Cray >>vector box. > >Actually todays clusters deliver a factor 1000 more or so. > >Total bandwidth a cluster can deliver is measured nowadays in Terabytes per >second, with Cray it was measured in gigabytes per second. Let's see. The last Cray I ran on with a chess program was a T932. Processor could read 4 words and write two words per cycle, cycle time was 2ns. So 6 words, 48 bytes per cycle, x 500M cycles per second is about 2.5 gigabytes per second, x 32 processors is getting dangerously close to 100 gigabytes per second. A "cluster" can have more theoretical bandwidth, but rarely as much _real_ bandwidth. This is on a shared memory machine that can do real codes quite well. > >Note it's the same network that gets used for huge Cray T3E's, but a newer and >bigger version, that's all. T3E isn't a vector computer. > >Crays had usually when in vector like what was is 4 cpu's or so? Sometimes up to >128. Above that it was T3E which had alpha's. > >that one used quadrics usually :) > >However look to France now. New great supercomputer. 8192 processors or so. >Say 2048 nodes. You're looking at 3.6 TB per second bandwidth :) > For a synthetic benchmark, not a real code, that's the problem with clusters so far... >Those Crays you remember were 100Mhz ones. Network could deliver of course >exactly what cpu could calculate. There was no "network" and the crays were 500mhz although on a fully pipelined vector machine that can do 5-10 operations per cycle that is not exactly a good measure of performance. > >Not so great if you look to the total number of Gflop it delivered. Nowadays the >big clusters, as all big supercomputers nowadays are clusters, are measured in >Tflop and one already in Pflop :) > >There is a 0.36 Pflop one now under construction :) > >Vincent Different computer for different applications. Ask a real programmer which he would rather write code for...
This page took 0.01 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.