On Fri, 18 Nov 2011 10:54:56 +0100 > Dear Pengju Ren, > when you increase the numebr of processors you increase the > available computing power, but also the amount of communications on > the network connectign those nodes. As the network has a finite > speed, there will be a point where the code looses more time > exchanging information between the cpus than doing any calculation. > > Possible solutions: > 1. use fewer cpus (between 8 and 160 there is plenty of space) > 2. try with a different number of pools (you could try > nkpoints*ncores_per_node) > 3. buy some faster network hardware > > best regards >
Dear Lorenzo Paulatto, Thanks for your kind answer. When I ran pw.x with 160 cpus it was about 10 times faster than with 8 cpus, I think the parallel efficiency is reasonable. So does gipaw.x need more communications between nodes than pw.x? Maybe the gipaw code could be improved by reducing the communication frequency. Best Wishes ================================================ ??? Pengju Ren renpj at dicp.ac.cn State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 zhongshan Road, Dalian, 116023, P.R. China
