On Tue, 30 Dec 2008, Wang Qinjing wrote: QW> Dear all:
QW> I noted that if I made calculation by pw.x in paralllel, there were QW> too many data communications between nodes. That was attributed to QW> the data communication of wave functions. There is a severe delay to QW> get information from these nodes. please provide more detail about the kind of job you are running, how you were running it and the kind of hardware you are running it on. there are several ways how you can improve parallel efficiency. please see the documentation and the many previous discussions on this topic and then make some scaling and performance tests to see how to run most efficiently. the best settings can vary a lot between different inputs and calculation types. QW> If I set disk_io='low', things are much better. But the main node this is only one option and indicates that you are most likely not running your job in a very efficient manner. QW> (or the first node) still has problem in net communication. I QW> noticed a charge density file is still written after each scf step. QW> Is that the problem? Or is there anything I can do to improve this QW> situation? there is a lot that can be done, but since you don't provide any information on what you are already doing, it is impossible to give any recommendation beyond urging you to (re-)read the documentation and FAQs. cheers, axel. QW> Thanks in advance. QW> QW> Yours Wang QW> QW> ------------------------------------ QW> ???????????????????????????? QW> Wang Qinjing, Physics Department, QW> Fudan University -- ======================================================================= Axel Kohlmeyer akohlmey at cmm.chem.upenn.edu http://www.cmm.upenn.edu Center for Molecular Modeling -- University of Pennsylvania Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323 tel: 1-215-898-1582, fax: 1-215-573-6233, office-tel: 1-215-898-5425 ======================================================================= If you make something idiot-proof, the universe creates a better idiot.