Merge pull request #2532 from h-vetinari/cuda118

add announcement to drop CUDA 11.8

Author: h-vetinari

news/2025-05-29-cuda-118.md

@@ -0,0 +1,83 @@
+# Dropping CUDA 11.8 as a default CUDA version
+
+CUDA 11.8 is the last holdover from the old days before conda-forge
+[switched](https://github.com/conda-forge/conda-forge.github.io/issues/1963)
+to the new and shiny CUDA 12+ infrastructure, where the CUDA toolchain
+is provided as native conda-packages, rather than a blob in an image.
+
+For CUDA-enabled feedstocks, we've been building both 11.8 and 12.6 by default
+for a while now, but many feedstocks (notably pytorch, tensorflow, onnx, jax etc.)
+have dropped CUDA 11.8 for many months already.
+
+Due to various constraints (details below), we are dropping CUDA 11.8 as a default
+version in our global pinning on June 5th. It will still be possible to opt into
+building CUDA 11.8 on a per-feedstock basis where this is necessary or beneficial.
+
+<!-- truncate -->
+
+The above-mentioned contraints are mainly:
+
+- it [complicates our pinning](https://github.com/conda-forge/conda-forge-pinning-feedstock/issues/6967) due to needing to switch images and compilers with 11.8.
+- it keeps us from [migrating](https://github.com/conda-forge/conda-forge-pinning-feedstock/pull/7005)
+  to newer CUDA 12.x versions necessary to support new architectures.
+- it's [not compatible with VS2022](https://github.com/conda-forge/conda-forge.github.io/issues/2138#issuecomment-2916743741), which is due to become the default toolchain on windows
+  in conda-forge soon (the previous VS2019 has reached end-of-life more than a year ago).
+- it complicates our infrastructure in several places, due to the big differences between the
+  before/after of the new CUDA architecture.
+
+After we have removed CUDA 11.8 from the pinning, any feedstock still building that version
+will drop the respective CI jobs upon rerendering. For feedstocks wanting to keep building
+CUDA 11.8 a bit longer, here's a sample configuration you can put under
+`recipe/conda_build_config.yaml` (and then rerender).
+
+```yaml
+cuda_compiler:
+  - None
+  - nvcc                    # [linux or win]
+  - cuda-nvcc               # [linux or win]
+cuda_compiler_version:
+  - None
+  - 11.8                    # [linux or win]
+  - 12.4                    # [linux and ppc64le]
+  - 12.8                    # [(linux and not ppc64le) or win]
+
+# use the same 11.8-enabled image for all variants (changes to ubi8,
+# down from default alma9, also for non-CUDA and CUDA 12 builds)
+docker_image:                                               # [linux]
+  # CUDA 11.8 builds
+  - quay.io/condaforge/linux-anvil-x86_64-cuda11.8:ubi8     # [linux64 and os.environ.get("BUILD_PLATFORM") == "linux-64"]
+  # CUDA 11.8 arch: native compilation (build == target)
+  - quay.io/condaforge/linux-anvil-aarch64-cuda11.8:ubi8    # [aarch64 and os.environ.get("BUILD_PLATFORM") == "linux-aarch64"]
+  - quay.io/condaforge/linux-anvil-ppc64le-cuda11.8:ubi8    # [ppc64le and os.environ.get("BUILD_PLATFORM") == "linux-ppc64le"]
+  # CUDA 11.8 arch: cross-compilation (build != target)
+  - quay.io/condaforge/linux-anvil-x86_64-cuda11.8:ubi8     # [aarch64 and os.environ.get("BUILD_PLATFORM") == "linux-64"]
+  - quay.io/condaforge/linux-anvil-x86_64-cuda11.8:ubi8     # [ppc64le and os.environ.get("BUILD_PLATFORM") == "linux-64"]
+
+# CUDA 11.8 is not compatible with current compilers
+c_compiler:                 # [win]
+  - vs2019                  # [win]
+cxx_compiler:               # [win]
+  - vs2019                  # [win]
+c_compiler_version:         # [linux]
+  - 13                      # [linux]
+  - 11                      # [linux]
+  - 12                      # [linux and ppc64le]
+  - 13                      # [linux and not ppc64le]
+cxx_compiler_version:       # [linux]
+  - 13                      # [linux]
+  - 11                      # [linux]
+  - 12                      # [linux and ppc64le]
+  - 13                      # [linux and not ppc64le]
+fortran_compiler_version:   # [linux]
+  - 13                      # [linux]
+  - 11                      # [linux]
+  - 12                      # [linux and ppc64le]
+  - 13                      # [linux and not ppc64le]
+```
+
+Due to changes in the pinning structure (which keys are zipped together), it's possible that
+further adaptations are necessary; you can ping conda-forge/core for that. Also, please let us
+know in the [issue](https://github.com/conda-forge/conda-forge-pinning-feedstock/issues/7404)
+if your feedstock still needs to support CUDA 11.8 and why (later down the line we'll want to
+drop support also in conda-forge-ci-setup, and knowing what feedstocks - if any - still need
+CUDA 11.8 will help guide the decision on timing).