Hello Chi Hin,

 

Thanks for the info and I ran the the solver with AcousticSolver --set-start-time 0.

With this flag, I don’t see the error.

 

I have attached here a tar ball which contains a modification of one of the test cases that came pre-packaged with the source code.

 

The test case is first run for 0.001 with sampling every 20 time-steps. This is followed by sampling phase which is again simulated for 0.001 seconds. So, the FinTime = 0.002 seconds. The solution is again sampled every 20 time-steps.

 

The tar ball contains two folders

 

Both the folders contain .out files where the output from the HPC run is written. The error is shown in the .out file in the sampling_run directory.

 

Regards,

Ishan

PGR

 

From: Chan, Chi Hin <chi.chan19@imperial.ac.uk>
Sent: 27 November 2024 23:40
To: Nande, Ishan A. <ian9@leicester.ac.uk>; nektar-users <nektar-users@imperial.ac.uk>
Subject: Re: Restarting the solution from previous time-step

 

 

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Hi Ishan,

 

The error message you received is typically due to FinTime < timestamp of the initial condition. But it seems that this shouldn’t be a problem from your description as FinTime = t_init + t_sampling with the initial condition at t_init, so I’m not entirely sure. 



Perhaps for a quick workaround, could you try adding a flag to AcousticSolver --set-start-time 0 for your sampling simulation and see if that works.



Could you also share the example setup you have so that I can have a deeper look into it? 



Cheers

Chi Hin

From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Nande, Ishan A. <ian9@leicester.ac.uk>
Sent: Wednesday, November 27, 2024 10:53:34 PM
To: nektar-users <nektar-users@imperial.ac.uk>
Subject: [Nektar-users] Restarting the solution from previous time-step

 

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Hello,

 

I am solving Linearized Euler Equations using the AcousticSolver  on the cluster and I have encountered an issue.

 

I am running initial calculations using a few time steps. The last time-step’s field files are provided as an initial condition for the solution sampling phase of calculations.

 

Let’s say that the initial run’s total simulation time is t_init  and the same for next phase of simulations is t_sampling.

 

These are the key-points of my setup :

  1. In my initial run’s session file the FinTime is set as t_init. For the sampling run, the FinTime is set as t_init  + t_sampling
  2. I am running the calculations in parallel and hence, the last time-step’s folder( which has .chk in it’s name) from the initial run is supplied to the InitialConditions field in the session of sampling run.
  3. The time step for initial and sampling runs is the same.

 

With the previously outlined setup, I have found that while the sampling phase of simulation run’s for the desired total time of t_init + t_sampling , it gives the following error:

Fatal   : Level 0 assertion violation
m_timestep < 0

I have replicated the exact same setup on one of the example cases and it results in the same error. What does this error mean ?

 

Can someone please comment on what could be going wrong ?

 

Regards,

Ishan

PGR