On Mar 25, 2011, at 13:58 , Gabriele Sclauzero wrote: > Before moving some complaints to the sysadmins, I would like to have > some feedback from those of you who have used this kind of > architecture. > Are you aware of similar kind of I/O issues? Is there any performance > tuning that can be done on the software/compiler side?
I also noticed that reading/writing the CP restart file on a BG takes a sizable amount of time, in the order of a few minutes for a typical system suitable for BG. I had attributed this to the "gathering" of the distributed pieces of wavefunctions that are subsequently written to file by a single process, though; in your case, it is the I/O by each process that takes a lot of time. You may want to try to reduce the I/O to the strict minimum: work with one k-point per processor (use k-point parallelization if needed), use disk_io='low' (or 'none'): the code should write only at the end (or never). P. --- Paolo Giannozzi, Dept of Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
