unhelpful ReadOnlyMemoryError message

[gaelforget]

I am trying to differentiate this function (main branch) and use the resulting adjoint.

using ECCO, Enzyme
x=[0.004]
glacier_ad(x)=autodiff(Reverse, ECCO.glacier_model.integrate, Active(x[1]))
glacier_ad(x)

The autodiff step does return a function,glacier_ad, but this function errors out, and I have no idea what to do to resolve the issue.

julia> glacier_ad(x)
ERROR: ReadOnlyMemoryError()
Stacktrace:
 [1] forward_problem
   @ ECCO.jl/src/mountain_glacier.jl:19

I looked through the docs of Enzyme.jl and searched for ReadOnlyMemoryError via github but did not immediately find any help.

How should I proceed to debug this? Where is the error message actually coming from? Am I missing something obvious?

Please advise.

[wsmoses]

That error is being thrown by Julia itself, not Enzyme.

Do you have a stacktrace or error log?

[gaelforget]

Thank you very much for the quick feedback.

The above is all the whole error message / stack trace.

Maybe a hint as to what happens : setting the number of time step is set to 6*5000 works, but at 8*5000 I get the above error message.

Does this make sense to you?

[gaelforget]

• I just pushed (this commit) a version that works by setting nt=6*5000 here
• To reproduce the error it suffice to edit the file and set nt=8*5000, e.g. with Revise.jl

[gaelforget]

• Should have probably mentioned that results reported above were done with Version 1.10.5.
• with Version 1.11.0 , the nt=6*5000 test crashes Julia as seen in this CI run
• but it seems that Enzyme + 1.11 has broader issues based on that CI run

[wsmoses]

Will need to investigate this further, but perhaps it's useful to apply Checkpointing.jl on your timestep loop?

Enzyme hasn't yet adapted to 1.11 changes so the 1.11 error is expected (and you should use 1.10 for now)

cc @swilliamson7 @heimbach @michel2323