CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

CPU Time using time command of unix

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   November 10, 2002, 12:56
Default CPU Time using time command of unix
Vinay Kumar
Posts: n/a
I want to compare the performance of two different programs for matrix inversion. Somebody suggested me that one can do so by comparing CPU time using time command ($time a.out). But it gives three times (real, user, sys) and I don't understand which time is to be compared.

Please help.


  Reply With Quote

Old   November 10, 2002, 13:28
Default Re: CPU Time using time command of unix
Posts: n/a
Most time the following relation is correct. real = user + system I always use user time if I am trying to tune the code, just like your current situation . But for actual purpose , for example , the total runnning time of my RANS3D code, I just use real time.
  Reply With Quote

Old   November 12, 2002, 09:42
Default Re: CPU Time using time command of unix
Posts: n/a
"user" time is the CPU time used to perform any tasks in so-called user space (including all the actual calculation etc). "system" time is the CPU time used to perform any system calls in the kernal space (such as "read" or "write" system call).
  Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
TimeVaryingMappedFixedValue irishdave OpenFOAM Running, Solving & CFD 28 May 28, 2015 13:37
Computational time sunnysun OpenFOAM Running, Solving & CFD 5 March 16, 2009 04:32
The method of Checking the CPU time JunYoung Park Main CFD Forum 2 April 19, 1999 15:34
On the reduction of cpu time lee Main CFD Forum 4 March 7, 1999 23:02
cpu time Gengsheng Wei Main CFD Forum 1 November 19, 1998 16:22

All times are GMT -4. The time now is 17:01.