An example implementing a new kernel

[jasalper]

Hi - it'd be super useful to see an example implementing a new kernel (or a re-implementation of an existing one that doesn't rely on the implementation in green-kernels).

It's not quite as simple as just implementing the Kernel trait in green-kernels. It seems like the kifmm crate itself also has a bunch of trait implementations for existing kernels (e.g. for TargetTranslationMetadata, etc), that it'd be useful to see in one spot everything that is needed to replace the kernel.

[jasalper]

To illustrate some of the issues I've run into:

I'm trying to implement a Laplace2d Kernel, but using it in Kifmm seems to require (?) that I implement

impl<Scalar, FieldTranslation> SourceTranslationMetadata
    for KiFmm<Scalar, Laplace2dKernel<Scalar>, FieldTranslation>

However, because SourceTranslationMetadata and KiFmm are both defined in the kifmm crate, I can't implement the trait. So it appears that without forking the crate, (and possibly green-kernels along with it), I can't add my own kernel.

[skailasa]

Hi @jasalper , wow awesome to see what you're trying to do.

Yes, there are a number of required traits for developing support for a custom kernel - not just the kernel trait, and the redefinitions must be added directly to this crate and require a fork. I haven't got the capacity to document this at the moment, but I would be happy to jump on a call with you to explain how to do it, and maybe we can work on it together. Feel free to reach out to me at sk937@cam.ac.uk

As another resource, the final chapter in my phd thesis contains more explanations of how everything fits together.

https://scholar.google.com/citations?view_op=view_citation&hl=en&user=iKP_0P4AAAAJ&citation_for_view=iKP_0P4AAAAJ:qjMakFHDy7sC

[jasalper]

Thank you!

I'm a little busy the next couple of weeks but will reach out once I have some more time :)