Serialise individual benchmarks seperately and plot collectively

[bjlittle]

@nschloe Thanks for perfplot, it's lovely 👍

I do have a use case for you that's not quite handled, but could be quite easily.

See https://github.com/bjlittle/bench/blob/main/README.md

Essentially, I'm using perfplot to benchmark OpenGL performance, but on separate hosts. Therefore, it's not possible to run perfplot in one single session.

Ideally, I'd like to use perfplot to run the same kernels, but on separate hosts. Then load all the benchmark results together in order to generate one single plot showing all the trends, rather than one plot per platform/host.

Unless you currently have a way to do this, it seems like it would be easy to extend perfplot to support serialising all kernel results for a session, say as yaml or json, then later load all serialisations to generate a single plot.

Let me know what you think or recommend.

Happy to push a pull-request to do this, or leave you to do this, if you feel this is a use case you'd like to support.

Thanks again 😀