Add Eiger and Instructions to compile ICON

docs/alps/SUMMARY.md

@@ -1,2 +1,3 @@
 * [Alps](index.md)
-* [Santis](santis.md)
+* [Santis](santis.md)
+* [Eiger](eiger.md)

docs/alps/eiger.md

@@ -0,0 +1,117 @@
+# Eiger
+
+Eiger is an Alps cluster that provides compute nodes and file systems designed to meet the needs
+of CPU-only workloads for the HPC Platform. For more information, please refer to the
+[CSCS Documentation](https://docs.cscs.ch/clusters/eiger/).
+
+C2SM only provides partial support for Eiger. Nevertheless, below you can find instructions on how
+to set up ICON on Eiger.
+
+## Setting Up ICON with Spack on Eiger
+
+### 1. Pull and Start the Environment
+
+```bash
+uenv image pull prgenv-gnu/24.11:v1
+uenv start --view=spack prgenv-gnu/24.11:v1
+```
+
+### 2. Clone and Setup Spack
+
+```bash
+git clone -b releases/v0.23 https://github.com/spack/spack
+source spack/share/spack/setup-env.sh
+```
+
+Set spack system config path:
+
+```bash
+export SPACK_SYSTEM_CONFIG_PATH=/user-environment/config/
+```
+
+
+### 3. Modify Compiler Flags for ICON
+
+Edit the file: `spack/var/spack/repos/builtin/packages/icon/package.pypackages.py`
+
+Add the following under the line `if self.compiler.name == "gcc":`:
+
+```python
+flags["LDFLAGS"].append("-Wl,--copy-dt-needed-entries")
+flags["ICON_FCFLAGS"].append("-fallow-argument-mismatch")
+flags["ICON_OCEAN_FCFLAGS"].extend([
+    "-O3",
+    "-fno-tree-loop-vectorize",
+    "-fallow-argument-mismatch"
+])
+```
+
+### 4. Create and Configure Spack Environment for ICON
+
+```bash
+spack env create my-icon
+```
+
+Modify the `spack.yaml` file in your `my-icon` environment. Example:
+
+```yaml
+# This is a Spack Environment file.
+#
+# It describes a set of packages to be installed, along with
+# configuration settings.
+spack:
+  specs:
+  - icon+art+rte-rrtmgp+grib2 -ocean ~coupling
+  view: true
+  concretizer:
+    unify: true
+  develop:
+    icon:
+      spec: icon +rte-rrtmgp +art +grib2 -ocean ~coupling
+      path: /capstor/store/cscs/empa/em05/ckeller/icon-kit
+  compilers:
+  - compiler:
+      spec: gcc@=7.5.0
+      paths:
+        cc: /usr/bin/gcc
+        cxx: /usr/bin/g++
+        f77: /usr/bin/gfortran
+        fc: /usr/bin/gfortran
+      flags: {}
+      operating_system: sles15
+      target: x86_64
+      modules: []
+      environment: {}
+      extra_rpaths: []
+  - compiler:
+      spec: gcc@=12.3.0
+      paths:
+        cc: /usr/bin/gcc-12
+        cxx: /usr/bin/g++-12
+        f77: /usr/bin/gfortran-12
+        fc: /usr/bin/gfortran-12
+      flags: {}
+      operating_system: sles15
+      target: x86_64
+      modules: []
+      environment: {}
+      extra_rpaths: []
+```
+
+!!! warning "Path to ICON code"
+    Ensure `develop.icon.path` points to your local ICON source code.
+
+### 5. Activate the Environment
+
+```bash
+spack env activate path/to/my-icon
+```
+
+### 6. Concretize and Install Packages
+
+```bash
+spack concretize
+spack install
+```
+
+`concretize` resolves dependencies, and `install` builds the packages.