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Meeting News


There will be a PPP this week.
[Monica]: Ruban - University of Amsterdam - Using GPU as a decompression accelerator next week.



Few talks related to RNTuple:

Talks on ML:







1) Varied snapshot:
- Process output file separately. Different cardinalities and can be worked separately.

[Philippe]: This requires some duplication of data.
[Florine]: If you have T3 index you can only write the varied parts and can work around it.
[Philippe]: We still have duplicated all the sparse data, but right.
[Vincenzo]: They want to reconstruct data in a generic way, with some performance issues. It's worth a try and worth benchmarking.

2) Objectification of NanoAOD inputs.

[Jacob] Situation is much better than expected; there is a way to do it, but for CMS users, it's ok.
[Vincenzo] Bamboo is a whole framework on top of CMS. It's always a bargain.
[JonasH] Don't use objects if you need performance.

Impact of Cppy Upgrade:

Summary: In fact, Cppy has many parts python library, C++ extension, and wrapper around cling - this has root-meta. Synchronizing with upstream expect the part taken from ROOT meta and cling.

Implicit conversion of std:: string to Python string.

"Strict" memory policy

[Jacob]: This is a bit strange this heuristics when you look from the C++ perspective.
JonasR: There are some void pointer cases in the early versions of pyroot. It would not be difficult to go to strict memory policy.
[Vassil]: One can implement an LLVM pass if we see delete. Some annotation will be useful on the interfaces.
JonasR: We can annotate at the python level but it would be difficult, it would be nice to do it at C++ level
[Vincenzo]: Solution - set memory policy to strict by default. It only applies to older parts of root. It seems to me that it is, a clang annotation is an overkill.
[Jacob]: What about third parties that depend on this case.
[Vincenzo]: Anything/framework based on older pyroot before a certain point is going to break.
[Vassil]: It is very important to add annotations - nullability and ownership. If this is going to be null, then don't call.
[JonasH]: If we the APIs want to make sure there are no null pointers it should be a reference.
[Vincenzo]: Clarification: There is already an existing infrastructure so that we don't need any extra work need to do make this happen?

No implicit conversion for char to null

JonasR If it's not null-terminated Cppy already knows it. You can work around that
[JonasH]: Do we do this right now?

JonasR: In root we have some unit test with char buffers that contain country code - had to add asterisks to make it work.

- Just run the test but show that numbers. Compared the runtime with and without the upgrade, but it's basically the same.
JonasR: It could be that the implicit conversion isn't done anymore that might be the explanation for some improvement.
JonasR: We still have 2 months before release, we have time to fix it, if there are any.

- memory - stick with current heuristics - with next release change.
- remove implicit conversion.

[JonasH]: Are all the corner cases solved?
JonasR: There's even less tests failing than before.
[Vincenzo]: For further developments - we only have a patched cling wrapper, anything else in the Cppy stack is the same?
JonasR: No, there are some changes and reverts. Implicit std namespace is an example, TString needs a custom converter. ROOT type alias is long64_t etc.
[Vincenzo]: We can do something similar to what we did for LLVM. Create a monorepo and replicate what we did.
JonasR: All the patches are in one directory. Everything is traced.
[Vassil]: Real problem is going to be in the backend, for IO we want one thing. It is going to converge.
{Discussions without converging on a solution for future upgrades}
[Jacob]: Question of handling future upgrades we move it to the next slot or another meeting.


[Meeting Ended]