Develop guidance for support for older linux-x86 processor variants

[johnkerl]

From time to time we have questions like this:
chanzuckerberg/cellxgene-census#1121

Issues involved:

• TileDB Core, TileDB-Py, TileDB-R, and TileDB-SOMA (Python and R) have precompiled binaries for OS the major architecture:
  • linux-x86 fully supported
  • macos-x86 fully supported
  • macos-arm64 fully supported
  • linux-aarch64 support is forthcoming: Formalize linux-aarch64 support #2482
• Issue here is support for processor variants within linux-x86
  • Symptom is Illegal instruction (core dumped) (see here for example)
  • The binaries we have pre-compiled for include certain instruction sets
  • Sometimes users run in environments not containing support for some newer instructions

Work to do:

• We need to decide, and document, which processor variants we support -- and "support" means:
  • Necessarily people will need to build from source -- since our precompiled binaries aren't right for older variants
  • People will need clear build-from-source instructions
• We need to decide, and document, which processor variants we don't support -- and that means:
  • Listing out processor variants for which we don't have a suggested recipe, and for which we don't intend to develop one

[sc-47640]

[eddelbuettel]

One small addition: The TileDB-R package has long used dual binary artifacts for x86_64 Linux provided by TileDB Embedded at each release. These artifacts differentiate between default and 'no AVX2' (same as the issue that spawned this) so on builds from R where artifacts are pulled in, the non-AVX2 machines are accomodated.

[rcurrie]

I was able to build and run from source on an old AMD Opteron(tm) Processor 6380 - specifically to use cellxgene-census. Order is install cellxgene-census and then build TileDB from source.

[eddelbuettel]

@rcurrie Awesome. If it is still fresh in your mind please do feel free to drop us a few bullet points about possible plusses or minusses of our docs with respect to building from source.

[rcurrie]

@eddelbuettel Docs work as advertised! Maybe add something like this (which I've added to the repo I'm working on using cellxgene-census):

TileDB-SOMA python wheels assume AVX2 generating an illegal hardware instruction (core dumped) on CPUs without AVX2 (cat /proc/cpuinfo | grep avx2 } head -1). To run on non-AVX2 cpus, build from source and install into your existing python environment or active virtualenv via:

git clone https://github.com/single-cell-data/TileDB-SOMA.git
pip install -v -e TileDB-SOMA/apis/python

[johnkerl]

@rcurrie I have the following up for review/comment:
#2643
https://github.com/single-cell-data/TileDB-SOMA/blob/kerl/older-arch-advice/apis/python/README.md