Troubleshooting CMake 4.x Build Issues With Palace

Hey guys! Ever run into those pesky build issues when trying to compile your projects? Today, we're diving deep into some common CMake 4.x build issues encountered while building Palace, a high-performance finite element analysis software. If you're wrestling with similar problems, you're in the right place! We'll break down the errors, understand the warnings, and, most importantly, explore how to fix them. So, grab your favorite beverage, and let's get started!

Introduction to CMake and Palace

First off, let's quickly introduce the key players here. CMake is a cross-platform, open-source build system generator. It's like the conductor of an orchestra, making sure all the instruments (your code and dependencies) play together harmoniously. It doesn't build the software itself; instead, it generates the build files (like Makefiles) that your native build tools then use. Palace, on the other hand, is a powerful finite element analysis software designed for high-performance computing. It's used in various engineering and scientific fields to simulate complex physical phenomena.

Building Palace often involves managing numerous dependencies, which are external libraries that Palace relies on to function correctly. These dependencies can sometimes be tricky to handle, especially when using newer versions of CMake. One common challenge is compatibility issues between the dependencies themselves and the build system. When you are using CMake, you might come across various errors and warnings, and that's exactly what we are going to discuss today.

The ScaLAPACK Error: A Compatibility Conundrum

The first major issue encountered was with ScaLAPACK, which stands for Scalable Linear Algebra PACKage. It’s a library for high-performance linear algebra computations on distributed memory systems. The error message pointed to a problem during the configuration stage, specifically with the cmake_minimum_required command within the BLACS (Basic Linear Algebra Communication Subprograms) installation process. The error message is pretty explicit:

CMake Error at CMakeLists.txt:1 (cmake_minimum_required):
 Compatibility with CMake < 3.5 has been removed from CMake.

 Update the VERSION argument <min> value. Or, use the <min>...<max> syntax
 to tell CMake that the project requires at least <min> but has been updated
 to work with policies introduced by <max> or earlier.

 Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.

This error essentially means that the version of CMake required by ScaLAPACK (or, more accurately, its build scripts) is older than the version being used (CMake 4.0). CMake is telling us that it no longer supports compatibility with versions older than 3.5. So, what’s the fix? There are a couple of ways to tackle this:

1. Updating the cmake_minimum_required version: The most straightforward solution is to modify the CMakeLists.txt file in the BLACS source code to specify a minimum CMake version of 3.5 or higher. This involves finding the line that looks like cmake_minimum_required(VERSION x.x) and changing it to cmake_minimum_required(VERSION 3.5). However, this might not always be feasible, especially if you're dealing with a library you don't want to modify directly.

2. Using CMAKE_POLICY_VERSION_MINIMUM: Another approach, as suggested by the error message itself, is to add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to your CMake configuration command. This tells CMake to behave as if the minimum required version is 3.5, potentially resolving the compatibility issue without modifying the source code. This is a cleaner approach as it doesn't require altering the library's files.

3. Checking for existing Issues: The user in the original report correctly identified a related issue on the ScaLAPACK GitHub repository (https://github.com/Reference-ScaLAPACK/scalapack/issues/135). This is a crucial step in debugging – always check if someone else has already encountered and potentially solved the same problem! The fix might involve patching ScaLAPACK or using a specific version that's compatible with your CMake version. Also, ensure that the minimum CMake version in the main CMakeLists.txt of your project is compatible with the versions required by all dependencies.

Navigating CMake Deprecation Warnings: Arpack-ng, Eigen, ParMETIS, and METIS

Besides the ScaLAPACK error, the build process also threw a series of CMake Deprecation Warnings for other packages like Arpack-ng, Eigen, ParMETIS, and METIS. These warnings look similar:

CMake Deprecation Warning at CMakeLists.txt:1 (cmake_minimum_required):
 Compatibility with CMake < 3.10 will be removed from a future version of
 CMake.

 Update the VERSION argument <min> value. Or, use the <min>...<max> syntax
 to tell CMake that the project requires at least <min> but has been updated
 to work with policies introduced by <max> or earlier.

These warnings are CMake's way of saying,