Re-starting LS-DYNA from a check-point

[Nava Farhadzadeh]

Hi Len and James

I am currently running my model on a system that only allows run for 96 hours, my LS-DYNA file with small elements take much longer than that to run. One way I have found to allow to run it longer on the system is to interrupt LS-DYNA and re-start from a checkpoint.

Just wondering if LS-DYNA allows checkpointing i.e. if does a full run output periodically then I can re-start my simulation from that checkpoint.

Just wondering if you know anything about this? Do you know what the command is?

Kind regards 

Nava

[l...@schwer.net]

See *DATABASE_BINARY_RUNRSF in the User Manual Volume I

                --len

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[James M. Kennedy]

Dear Nava,

 

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Two types of dump files (d3dumpxx or runrsf) using either of the following data entries

 

*database_binary d3dump or

 

*database_binary_runrsf

 

can be written (saved).

 

The dump files write all the state variables values from your simulation at a particular integration cycle which will allow you to continue your simulation from that cycle, if your simulation has for some reason been unexpectedly terminated (power outage, program error, stability, etc.). Continuation of the simulation (changes allowed), called restarts, allow for changes in the input data.

 

I often suggest using the running restart dump, runrsf. This approach will write only one restart file (saves space) instead of multiple restart files when you use the d3dump option..

 

*database_binary_runrsf

$ dt/cycl

5000

 

The example entry of 5000 represents the output interval, in number of cycles (a cycle is a time step), that LS-DYNA will write out the restart file.

 

I probably would write a restart every six hours or so. Estimate the number of time steps it would take to achieve six hours of CPU and enter that as your output interval. You can increase or decrease the cycle interval as you see fit.

 

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Another short note.

 

The D3DUMP and the RUNRSF options create complete databases which are necessary for restarts. See *RESTART. When RUNRSF is specified, the same file is overwritten after each interval, unless the field NR is set which causes a series of restart files to be overwritten in a cyclic order. When D3DUMP is specified, a new d3dump file is created after each interval. After the first interval LS-DYNA will write d3dump01, after the second d3dump02 and so on. The default file names are runrsf and d3dump unless other names are specified on the execution line, see the GETTING STARTED, EXECUTION SYNTAX. Since all data held in memory is written into the restart files, these files can be quite large and care should be taken with the d3dump files not to create too many. If *DATABASE_BINARY_D3PLOT is not specified in the keyword deck, then the output interval for d3plot is automatically set to one twentieth of the termination time.

 

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Two comment comments regarding small restarts:

1. If you stopped your calculation prior to your original termination time, you can simply restart using the last saved d3dumpxx file with no input file needed.
2. If you stopped your calculation due to reaching your original termination time,

you can simply restart using the last saved d3dumpxx file and a new restart input deck; example given here:

*KEYWORD
*CONTROL_TERMINATION
[new termination time]
*END

 Please see pages 2-21 and 2-22 in the latest LS-DYNA User’s Manual for execution syntax for Restart Analysis:

http://ftp.lstc.com/anonymous/outgoing/jday/manuals/DRAFT_Vol_I.pdf

Some older notes that might be helpful:

Day, J., “Restarting LS-DYNA”.

http://ftp.lstc.com/anonymous/outgoing/jday/restart.pdf

Sincerely,

James M. Kennedy

KBS2 Inc.

December, 22, 2021

 

 

From: ls-d...@googlegroups.com [mailto:ls-d...@googlegroups.com] On Behalf Of Nava Farhadzadeh
Sent: Wednesday, December 22, 2021 5:28 AM
To: LS-DYNA2 <ls-d...@googlegroups.com>
Subject: [LS-DYNA2] Re-starting LS-DYNA from a check-point

 

Hi Len and James

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[Kağan GENÇ]

Hi Leonard and Kennedy,

I am simulating a blast explosion with MM-ALE method on a slab. Due to the power cutoff,  the run has been cut at the middle of the analysis which takes too much time. Fortunately, I used the keyword namely *DATABASE_BINARY_RUNRSF. As I know, RUNRSF or DUMP options can be used to restart run. Because of excessive storage allocation of DUMP files with the keyword namely *DATABASE_BINARY_D3DUMP, I preferred to use just the keyword namely *DATABASE_BINARY_RUNRSF which overwrites ever step on a file in a cyclic manner. However, in the previous info shared in this group, it is not mentioned how to restart from *DATABASE_BINARY_RUNRSF. No 'd3dump' file is written as output by this keyword but just one 'runrsf' file is written. What command should I use to restart my run from 'runrsf' file? 

Kind regards,

GENC OGUZ KAGAN

22 Aralık 2021 Çarşamba tarihinde saat 23:08:47 UTC+9 itibarıyla L...@Schwer.net şunları yazdı:

[l...@schwer.net]

I believe you just replace the dump file name with that of the last running restart file name on the execution line, i.e. r=runrsfxx           --len

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[James M. Kennedy]

Dear Kagan,

October 14, 2022

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