caffe: use pre-CUDNN 8.x

[ConnorBaker]

Description of changes

Since #215578, the default for cudatoolkit 10.1 is CUDNN 8.0.5, the last version to support CUDA 10.1. However, caffe does not build with CUDNN 8.x, so we use CUDNN 7.6.5 instead. Earlier versions of cudatoolkit use pre-8.x CUDNN, so we use the default.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.05 Release Notes (or backporting 22.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[ConnorBaker]

Result of nixpkgs-review pr 217330 run on x86_64-linux 1

1 package marked as broken and skipped:

• python310Packages.caffeWithCuda

1 package built:

• caffeWithCuda

[ConnorBaker]

@abbradar @avitex would you mind giving this a quick once-over? The change is the addition of a conditional to ensure caffe isn't built with a version of CUDNN which is too new.

[samuela]

cc @NixOS/cuda-maintainers

[samuela]

Result of nixpkgs-review pr 217330 run on x86_64-linux 1

1 package marked as broken and skipped:

• python310Packages.caffeWithCuda

1 package built:

• caffeWithCuda

[ConnorBaker]

Removed the useless check in assert that CUDNN was of the correct version given that the let statement handles that.

Also removed the PR stack info in the header because it can be merged independently of the others.

[samuela]

Is there a reason to support cuda < 10.1? Why not just mark caffe as broken for cuda versions that are too old?

[ConnorBaker]

Maybe the way I wrote the if expression is weird -- CUDA 10.0 and all the prior versions of CUDA work fine because they only support up to CUDNN 7.6.5. (That's why we use their default cudaPackages.cudnn and don't need to fish around for a different version.)

CUDA 10.1 is special because it's the only release in the 10.x series to be supported by a version of CUDNN 8 (it's supported by CUDNN 8.0.5). So in the special case where we have 10.1, we need to fall back to the older version of CUDNN.

[samuela]

Ahh, I misunderstood -- thank you for explaining! Ok this LGTM then

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/tweag-nix-dev-update-45/26397/1