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Minutes from 125-th OpenVDB TSC meeting, March 22nd, 2022, (EDT)
Attendees: Ken M., Jeff L., Nick A, Dan B., Rich J., Andre P.
Additional Attendees: Sebastian Gaida, Serjio Rojas, Greg Hurst (United Therapeutics), Kyle Wardlow (United Therapeutics).
Regrets: None
Agenda:
- Confirm quorum
- Secretary
- Forum
- PRs
- vdb_tool update
- Threading and Interrupter
- Next meeting
- Confirm quorum
Quorum is present.
- Secretary
Secretary is Jeff Lait.
- Forum
a) Build Issue
Will be responded to.
b) Memory usage of a single point
Reported it takes 1.6mb used to allocate one voxel. The full internal leaves have a union, this non-trivial data type will be bloating the size of the internal nodes. Someone else should respond that this is expected. Ken to reply
c) How to use advection for VDB points
Code snippet unclear. Dan will look at.
d) Grid value assigned unexpected results
Not clear what they are referring to with the images. Jeff will reply to it.
- PRs
a) 1330: Updated UBSAN builds to fail on errors
Fixed most of the issues that can be fixed, suppressed the others, and added fail on error. So if we get any new undefined behaviour we'll trigger an error. Removes NanoVDB as there is a lot of UB in that.
b) 1334: AX improvements
For Richard to review. Updates point kernels to have same optimization as the volume kernels, to do the loops in LLVM rather than C++. Also adds codecs to AX to match VDB Points. This lets LLVM then do the optimization.
c) 1335: maxMemusage and TypeLists
Attempt to improve vdb_print's memory report. So we report delay-loaded data as maximum. Maximum could be confusing. But so are other possible choices, like "total". Also need an API method to return this, currently maxMemoryUsage. Perhaps "If Loaded" and "memUsageIfLoaded".
How to make a free standing function that can dispatch to the proper type of VDB? Traditionally we used virtual functions. This PR adds SupportedTypes as a type list that can be used when you apply.
We can then use apply<> and foreach<> to run dispatch. Ideally we could add SupportedGridTypes to the build process so custom grids can get access too.
Should it be AllGridTypes rather than SupportedGridTypes? Advantage of SupportedTypes is that are the types supported in default library tools.
d) PR1319 vdb_cmd relocation
Moves the command tools out from openvdb/openvdb/cmd to openvdb_cmd. Nick to look at. So vdb_tools will go to the new command folder. This allows our binaries to build after all tools, in particular ax.
- vdb_tool update
A new massive change is in-bound. Led down the rabbit-hole of Forth, there is a scripting language built with it. This clarifies a lot of the earlier decisions.
- Threading and Interrupter
threading = true is a dangerous way to set threading. Sometimes you want more grain sizes. And default parameters cause their own issues
- the nullptr from an interrupt got passed to the threading parameter so disabled threading.
We want to support different threading primitives in the future (other than TBB). We could demand a struct or object that defines state like threads/interrupter. Or we have a more global, some file-static data that sets threading levels.
There could be some context or state structure you have to specify. Morphology does some more dynamic scheduling that is hard to frame in terms of grain size. Often want to turn off threading at a top level and have everything below single threaded.
Maybe we have an enum with some policies. So threaded_8 rather than a separate 8 grain size parameter. We could have an enum with OFF and DEFAULT and then add policies as needed.
- Next meeting
Next meeting is at March 29th, 2022. 1pm-2pm EDT (GMT-4).