Issue with restarting AWI-CM-1 runs with a different leg length

[mathanase]

I have recently been trying to branch-off a simulation from a parent AWI-CM-1 run (on DKRZ Levante). The parent-run has a restart length of 1 day. For the simulations I am branching off, I was hoping to perform multi-days or 1-monthly leg lengths.
However, every single attempt ended with seemingly one component waiting for the other forever, and therefore the simulation hit the time limit.

See one example test runscript in:
/home/a/a270216/NRT/ERA5T_ENSEMBLE/runscripts/tests_extension
See also one example of failed experiment in:
/work/ba1264/a270216/NRT/runtime_ens/awicm1_T127L95_PD_T20_24H_20231208_20240108/awicm1_T127L95_PD_T20_24H_20231208_20240108_E1/

I suspect that doing a 1-month long leg starting not on the 1st of the month might be an issue too. Nevertheless, the multi-days option also does not work, so I am unsure what to do in this case.
I also may be doing something wrong here, but cannot figure out why.
If not, then it would be great to be able to change the restart length (from short to long) without issues. Note that changing from multi-days / multi-months length to daily was not an issue in the past.

FYI, @antoniofis10000 reported having faced similar issues in the past.
Thanks in advance!

[nwieters]

Hi @mathanase ,

would it be possible for you to quickly do a test, if branching off and changing from daily to monthly restarts would work if you start on a 1st of the month? Only if this is easily doable for you. If this is causing no error, we could then maybe narrow it down to the start date.

I will have a look on multi-days restarts.

Thank you.

[antoniofis10000]

Just to add. The multi-days issue is the same to #807.
However this issue is wider as reported by @mathanase as it also involve not able to do a 1-month leg starting not on the 1st of the month.

[mathanase]

@nwieters , Thanks for looking into this.

It is actually not that straightforward for me to restart on the 1st of the month. If it is important, I can try taking some intermediate steps to make that possible. But that would require some additional short runs.
And it might not solve the second part of the issue, which is "stopping before the end of the calendar month", right?

[nwieters]

Hi @mathanase ,
ok, I think I can reconstruct a similar experiment then myself.

One thing I tried so far is to run a simulation with 5days restarts with AWICM3 and the latest version of esm_tools. That works well. It also has no problems with runs that go over a month break (run_20000131-20000204).
With this run I just wanted to test if a multi-day restart it in general possible with esm_tools.

I will try this also with awicm-CMIP6.

Which esm_tools version are you using (esm_tools --version)?

I won't be here tomorrow but I will have a look again on Wednesday.

[mathanase]

I am using esm tools version 6.21.5.
Again I do not exclude to be doing something wrong here, but the "component freezing+time limit reached" makes it difficult to find out for sure what is going on...
Thanks a lot @nwieters

[nwieters]

Hi @mathanase ,
one question regarding the example you mentioned above.
From the log file

(/work/ba1264/a270216/NRT/runtime_ens/awicm1_T127L95_PD_T20_24H_20231208_20240108/awicm1_T127L95_PD_T20_24H_20231208_20240108_E1/log/awicm1_T127L95_PD_T20_24H_20231208_20240108_E1_awicm_compute_20231208-20240107_8403867.log)

it seems that it is actually starting the run correctly at 8.12.2023 but stops at the year break.

In the ECHAM stderr file

(/work/ba1264/a270216/NRT/runtime_ens/awicm1_T127L95_PD_T20_24H_20231208_20240108/awicm1_T127L95_PD_T20_24H_20231208_20240108_E1/run_20231208-20240107/work/echam.stderr)

there is a line saying:
Interrupt model, last prognostic date/time is: 1. Jan 2024 00:00:00

Could the time out be related to some files for year 2024 that are not found? E.g. nudging? Do you know if this could be the case?
Maybe ECHAM is stopping here and since the whole run would like to continue it is running into a time out here.

[nwieters]

Hi @mathanase ,
a small update on my last reply.

I am doing a run right now that starts from 8.12.2023 with a monthly restart but without nudging. And it looks as if it is hanging at the same step as yours. So my guess it now that ECHAM does not like restarts that include or go over a year break. I will do some more tests just to be sure.

[mathanase]

@nwieters I did find out that some nudging files were missing yesterday, but that did not resolve my own issues with monthly restarting from the middle of a month.
At the moment my "solution" is to keep running with a daily restarts, which is computationally inefficient, but at least it runs (so far)...

[antoniofis10000]

Hi @nwieters.
Regarding:
"Could the time out be related to some files for year 2024 that are not found? E.g. nudging? Do you know if this could be the case?
Maybe ECHAM is stopping here and since the whole run would like to continue it is running into a time out here.".

Using the same runscript from Marylou, I tried to run a similar run between 02 October 2023 to 01 November 2023 (/work/ba1264/a270148/Test1MonthF0210To0111) and the issue is the same. (It stuck at 00UTC 01 November, so 1 day before ending).

[nwieters]

Hi @antoniofis10000 , @mathanase , @mandresm ,

yes. I also get this behaviour without nudging. I tried monthly restarts and also restarts with 14 days but it is still hanging at the month break.
@antoniofis10000, I also find this 'Interrupt model ' error in your experiment
(/work/ba1264/a270148/Test1MonthF0210To0111/run_20231002-20231101/work/echam.stderr)
Can you confirm from previous failed examples that this is a problem that occurs always at the end of a month?

For me it seems that, for some reason and in some circumstances, ECHAM interrupts at a month break resulting in a hanging run. I will do some tests with ECHAM standalone to find out, whether a namelist entry is still not correctly set.

[antoniofis10000]

Hi @nwieters
I am not 100% sure about that but yes, in this experiment also the same issue emerges.

[nwieters]

Hi @mathanase , @antoniofis10000 ,

as we already discussed, I did a few test runs with ECHAM standalone (version echam-6.3.04p1 as in awicm-CMIP6).
In general, I was able to reproduce the behaviour you both described also with the standalone version. That is

1. not able to do a monthly (or yearly) restart for a run that starts other than on the 1. of the month (or year).
2. changing the restart rate or unit

To 1.: I am not really sure why, but it seems to me, that you need to initialize or restart always at the beginning of a restart unit (i.e. at the beginning of the day, month, or year), otherwise Echam will interrupt at the end of the chosen unit.

To 2.: It is possible to change the restart rate and unit, but there are some constraints to be considered:

• When restarting the simulation, Echam assumes that the rerun/restart events are calculated with respect to the overall start date of the experiment. This start date information is taken from the restart files.

  This means, when you change the restart rate on a restart you have to make sure, that your planned restarts fit to the restarts that Echam calculates with respect to the start date.

  Example: If you start/initialize the experiment on the 1.1.2000 and do two restarts with a restart rate '1' and unit 'month', you get two runs of length one month. If you now change the restart rate to '3', meaning you want to start the restart on 1.3.2000 and do a next restart on 31.5.2000, this will fail because Echam is calculating the next restart event with respect to the 1.1.2000, and will do a restart already on the 31.3.2000 and will then interrupt. What works is to have three one monthly restarts and then change to a restart rate of '3' because this fits to the overall start date 1.1.2000.

  I also tested this with restart unit 'days' and it showed the same behaviour.

In a coupled setup like awicm-CMIP6, the interruption of Echam will result in Fesom hanging while waiting for coupling data and eventually result in a time out.

I hope my explanation was clear to you. If not, please let me know or ask me directly.

In order to get more detailed information on Echam rerun events, you can turn on a debugging flag for this:
Add the following lines to your runscript in the echam section:

echam:
    add_namelist_changes:
        namelist.echam:
            runctl:
                ldebugev: ".true."

You will than find more information about Echam events in the echam6.log or echam.stderr file in your experiment (.../run_from-to/work/echam6.log, search for 'State of event <rerun interval>').

[nwieters]

Hi, I will for now turn this into a discussion. Please add more comments or raise another question if needed.