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PurdueME April 11, 2009 12:02

Time/iter
 
When printing the residuals during iterations, one of the things printed out is "time/iter". What does this number mean? For example, one iteration printed out 43:20:10. The iteration takes about one second, so I don't understand what that number means and I can't seem to find it online.

PurdueME April 13, 2009 15:06

Anyone have any idea?

ngrube April 13, 2009 20:02

To increase your chance of getting useful replies, you should tell us what program you are using, and what you are trying to use it for.

time/iter might mean something like CPU time per step or it could mean physical time per step.

In your case, unless you are dealing with some really big scales, neither makes much sense. If your simulation is crashing and generating NaNs, sometimes that can lead to an erroneously large delta t (computed from a CFL condition) for the next step. Perhaps that would give you a ridiculous number like you are reporting. If your simulation is running fine, then my guess would be that the number you see is simply incorrect and not worth worrying about. Or maybe there is some interpretation that I am overlooking. Obviously a manual is the best source of answers, and without knowing what program you are using, people probably can't help much.

PurdueME April 13, 2009 20:41

Wow, I didn't realize I never mentioned the program -- total oversight on my behalf.

I'm using Fluent 6.3 to run a steady turbulent model.

I'm referring to the print-out on the screen during iteration of a solution.

The iter continuity x-velocity y-velocity k epsilon time/iter line.

I understand all the others, obviously, but not the time/iter one.

ngrube April 13, 2009 21:02

Quote:

Originally Posted by PurdueME (Post 212754)
Wow, I didn't realize I never mentioned the program -- total oversight on my behalf.

I'm using Fluent 6.3 to run a steady turbulent model.

Okay. :-) Well, I should defer to people who use Fluent then. Even if you don't have a paper manual, for such a sophisticated program as that, I would be surprised if there isn't a manual available from a help menu or something.

PurdueME April 13, 2009 22:50

Quote:

Originally Posted by ngrube (Post 212756)
Okay. :-) Well, I should defer to people who use Fluent then. Even if you don't have a paper manual, for such a sophisticated program as that, I would be surprised if there isn't a manual available from a help menu or something.

Oh, I've looked through the documentation for it. Tried every corner of it that I could think of. Tried a Google search for it. Tried talking to my professor who uses it daily (he said he didn't even notice that it was there). It isn't so much a matter of technical importance as it is curiosity, honestly.

ngrube April 13, 2009 23:07

I wonder whether people who run Fluent on totally different machines get numbers that make more sense? If you are curious, you might try to find someone who uses as different an architecture as possible and ask them. It could be that however your system returns the system time info differs from what the Fluent programmers were expecting. I have seen garbage timing results in similar situations but I always just got the timing info in a different way rather than getting to the bottom of the mystery.

A_Lyaskin April 14, 2009 04:09

I'm not a Fluent user (BTW, why don't you try posting your question in Fluent forum, not in the general one?), but my guess that it can be CPU time passed from the beginning of the simulation till the end of the iteration.

jpando September 7, 2012 15:01

I think the time/iter is the total time left for how many iterations are left. i.e. 400:10:05 9910 will mean that there will be 400 hrs, 10 min, 5 sec, left to calculate 9910 iterations at the current iteration rate.

twolf59 July 1, 2015 11:22

A little late, but just want to say that this makes the most sense since the number appears to countdown from when I start my simulation.


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