Parallel performance -- CFD Online Discussion Forums

August 29, 2006, 22:02	I have a case of about 1M cell	#1
liu Senior Member Xiaofeng Liu Join Date: Mar 2009 Location: State College, PA, USA Posts: 118 Rep Power: 17	I have a case of about 1M cells. I run it parallel on 32 partitions (16nodes X 2cores = 32). I want to simulate a process which takes about 1800s in reality. I run the case on the supercomputer for 12hours. It only simulates about 600s. One thing I noticed is the time information in the log file: at time step n: ExecutionTime = 25185.6 s ClockTime = 43755 s at time step n+1: ExecutionTime = 25194.1 s ClockTime = 43769 s The clocktime is almost twice that of execution time. Does execution time means CPU time and clocktime means CPU time plus communication time between nodes? Does it mean the program spent a lot of time just on waiting for data transfer? __________________ Xiaofeng Liu, Ph.D., P.E., Assistant Professor Department of Civil and Environmental Engineering Penn State University 223B Sackett Building University Park, PA 16802 Web: http://water.engr.psu.edu/liu/

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