[petsc-users] Error with PetscMatlabEngineCreate

[Amneet Bhalla]

Thanks Barry. Adding absolute paths made it work with "master" hostname. We
have added both options in our code just in case the NULL hostname does not
work on a different machine.
https://github.com/IBAMR/cfd-mpc-wecs/blob/main/main.cpp#L346-L361

On Fri, Jun 10, 2022 at 1:48 PM Barry Smith <bsmith at petsc.dev> wrote:

>
>   Based on your report the issue is likely due to a MATLABPATH issue. The
> difference between using "master" and NULL is that when "master" is used,
> PETSc ssh's to "master" to startup the Matlab engine while with NULL it
> launches the Matlab engine directly from the current process in
> (presumably) the current directory.
>
>    When ssh is used it does not have information about the current
> directory nor would it have any tweaks you have made to your MATLABPATH in
> your shell. Thus it cannot find the script.
>
>    Thus when not using NULL you need to make sure that all scripts you
> plan to launch are findable in the MATLABPATH on the machine you are
> launching the Matlab engine, maybe by putting the directories in MATLABPATH
> on in your .bashrc or .profile file or whatever file gets sourced
> automatically when you ssh to master.
>
>   Barry
>
>  I have no explanation why the behavior would change with PETSc versions
> or Matlab versions but the above should resolve the problem; you may have
> previously just been "lucky" it could fine the script.
>
>
>
> On Jun 10, 2022, at 4:14 PM, Kaustubh Khedkar via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
> Hi all,
>
> I am using the Petsc’s Matlab engine to run some Matlab scripts from my
> c++ code.
>
> I have been using Petsc’s Github commit:
> 9babe2dd5ff256baf1aab74d81ff9ed4c6baba0b
> (HEAD -> master, origin/master, origin/HEAD)
> Merge: e9b74a6d12 bb2d6e605a
> Author: Satish Balay <balay at mcs.anl.gov>
> Date:   Fri Nov 6 17:46:10 2020 +0000
>
> I used the command:
>
> PetscMatlabEngineCreate(PETSC_COMM_SELF, "master", &(mengine));
>
> where, the hostname is master. (Verified by typing hostname in the
> terminal)
>
> Everything was working fine until I updated my PETSc version to 3.17.2.
> Using this version I get error using the command:
>
> PetscMatlabEngineEvaluate(mengine, "load_parameters;”);
>
> cannot read load_parameters script.  where, load_parameters is a Matlab
> script.
>
> When I switch the hostname to NULL from master as:
>
> PetscMatlabEngineCreate(PETSC_COMM_SELF, NULL, &(mengine));
>
> Everything starts working fine again. All of this was executed on the same
> machine.
>
> Has anything changed when using the PetscMatlabEngineEvaluate command?
>
>
> Thank you,
> Kaustubh Khedkar
>
>
>

-- 
--Amneet
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