Hello, I’m very new to posting questions on here so I apologize in advance for any formatting/convention mistakes or if anything is unclear!

I am trying to solve a PDE using MethodOfLines.jl and receive the following warning when I “discretize” the system: “Warning: The system contains interface boundaries, which are not compatible with system transformation. The system will not be transformed. Please post an issue if you need this feature.”

However, my boundary conditions (in my 2 “parameters” T and x; and for my 3 “variables” u(…), v(…), w(…)) are as follows:

```
ic_bc = [u(0,x) ~ 0.0, v(0,x) ~ 0.0, w(0,x) ~ 0.0, # initial conditions
u(T,minimum(xrange)) ~ u(T,maximum(xrange)), # periodic bcs
v(T,minimum(xrange)) ~ v(T,maximum(xrange)),
w(T,minimum(xrange)) ~ w(T,maximum(xrange))]
```

My questions are:

(1) Is there a simple reason why I am seeing this Warning? I was under the impression that periodic boundary conditions and initial conditions are both supported, and I believe that is what I have here.

(2) How concerned should I be about this Warning? Should this significantly impede the solver’s ability to correctly solve my PDE? When I try to “solve” anyways, a solution is indeed generated, but the solution is all 0’s (i.e. not what I would expect). I ask this because, if it is the case that this Warning should not negatively impacting the solver, I would need to search for other possible errors in my code/parameters.

Please let me know if posting more of my code or more details on my simulation would make this question clearer. For a little context, I am trying to solve the semiconductor Bloch equations in the length gauge. Any help would be much appreciated!