The "DT RESTART" how to restart

[Kanchi]

Hello, everyone.
I have a FDS instruction set:

& Time T_END = 120, DT = 0.1 /
& DUMP NFRAMES = 120, DT_RESTART = 20.0 /

I have a few questions of these two lines commands
1.FDS → computation time of 120 seconds
2.DT = 0.1 → I do not know what this means
3.DUMP NFRAMES = 120 → I do not know what this means
4.DT_RESTART = 20.0 / → once every 20 seconds record

* 5 If the file operator to 60 seconds, the machine or power to stop,
I follow the FDS operation?

[Barbro Maria Storm]

2012/4/15 Kanchi <kan.ki...@gmail.com>:

Excluding the first four questions, you should try to avoid having to
actually restart a file as it's not foolproof, and I've had trouble
with numerical instability more often with it in use than without.

--
Barbro Storm

[徐睦淵]

I just want to know the meaning of the Directive, as well as how to use DT_RESTART.

2012/4/15 Barbro Maria Storm <bar...@gmail.com>

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[Tony Bova]

Hello,

The version 5 user guide has information on all of these. You can search for key words in the pdf of the user guide. 

1: you are correct

2: see section 6.2.2, p. 28

3: see section14.1, p. 155

4: once every 20 s, a restart file is saved. See section 6.4.2, p.37

I'm not sure I understand your last question, but Barbro is right -- you should try to avoid using restart for now (eliminate DT_RESTART).

 
~tony

On Sunday, April 15, 2012 8:02:13 AM UTC-4, Kanchi wrote:

I just want to know the meaning of the Directive, as well as how to use DT_RESTART.

2012/4/15 Barbro Maria Storm <bar...@gmail.com>

2012/4/15 Kanchi <kan.ki...@gmail.com>:

> Hello, everyone.
> I have a FDS instruction set:
>
> & Time T_END = 120, DT = 0.1 /
> & DUMP NFRAMES = 120, DT_RESTART = 20.0 /
>
> I have a few questions of these two lines commands
> 1.FDS → computation time of 120 seconds
> 2.DT = 0.1 → I do not know what this means
> 3.DUMP NFRAMES = 120 → I do not know what this means
> 4.DT_RESTART = 20.0 / → once every 20 seconds record
>
> * 5 If the file operator to 60 seconds, the machine or power to stop,
> I follow the FDS operation?
>

Excluding the first four questions, you should try to avoid having to
actually restart a file as it's not foolproof, and I've had trouble
with numerical instability more often with it in use than without.


--
Barbro Storm

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[徐睦淵]

I want to know, when I set "DT_RESTART" directive, and how the line executed? (Temporarily not to discuss the results of the FDS simulation correctness)

Assume that the computing time of 120 seconds, DT_RESTART = 20, 60 seconds a computer crash, how do I use "DT_RESTART continue to converge to continue to carry out computing.

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[Tony Bova]

That's in section 6.4.2.  DT_RESTART just tells fds to write a file, with the suffix '.restart', to the working directory every 20 s (or whatever period you want) of simulation time. The restart file is overwritten every time it's saved. You can restart from the point that the last restart file was saved. For example, if your simulation went past 40 s, but crashed just before it got to 60 s, then you can restart from 40s. If you made it past 60 s, then you may be able to restart from there. The method for using the restart file is in 6.4.2.  

[徐睦淵]

Thank you for your reply, let me try it~

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