Error: no real evaluate for ConstantCF-Complex

NGSolve
1

Hi,

I am working with complex grid and coefficient functions and compositions thereof. In the final calculation, only the real part has physical significance. To speed up the evaluation, I would like to compile the resulting CoefficientFunctions.

I took the following steps:

  1. Define complex CF
  2. Take real part
  3. Compile
  4. Efficiently evaluate

Then the following error gets thrown: netgen.libngpy._meshing.NgException: no real evaluate for ConstantCF-Complex

I am using:

  • python version: 3.13.1
  • ngsolve version: 6.2.2406

A Minimum Working Example is given below. I also included a similar example of such an error for complex ScaleCF.
MWE_ngsolve_eval_complexCF.py (615 Bytes)

I believe that this is a bug. If this is intended behaviour, then I would like to know how to do this properly.

Best,
Gotya

2

the CompiledCF evaluates all steps in real, or all steps in complex arithmetic, the type of the final result decides. You can swap your step 2 with step 3 to evaluate everything with complex numbers:

B = A.Compile(realcompile=True).real

I want to add that complex compile is not heavily used, since time-harmonic problems usually don’t have complicated expressions. Let us know if you have an use case where the un-compiled evaluate is the bottleneck.

3

Thank you. I will try that.

Some background of my use case. I am writing a semi-analytical perturbative computational model using NGSolve. In this model, the nonlinear equations are divided into a sequence of ordered linear problems (assuming the nonlinearities are small). In this approach, solutions of lower-order problems are needed as forcing in subsequent higher-order problems. This dependence on previously computed solutions together with the semi-analytical expressions can become quite time consuming when using the un-compiled evaluate when solving the higher-order problems. Using an intermediate projection using Set or Project on a GridFunction makes solving the higher-order bilinear form take fractions of a second compared to tens of minutes. But then the projection step takes most time and may introduce small projection errors.