Debugging Spheral Build Issues On OpenHPC With Sundials

Are you wrestling with building Spheral on your local OpenHPC cluster? It's a common challenge, especially when dependencies like Sundials get involved. Let's dive into the specifics of your situation and explore some potential solutions to get your build process back on track. We'll focus on how to troubleshoot the Sundials build failure that you're encountering, providing you with actionable steps to diagnose and resolve the issue.

The Problem: Sundials and MPI on OpenHPC

Your core problem seems to stem from Sundials failing to detect a suitable MPI library during the build process, even though Spack (your package manager) appears to have identified the compiler and MPI instance correctly. This is a classic symptom of an environment configuration mismatch or a problem with how the MPI libraries are being made available to the build system. Let's break down the likely culprits and how to tackle them.

Firstly, it's great that you can build Sundials directly from the source directory with the same configuration options Spack passes to CMake. This confirms that the issue isn't fundamentally a problem with your MPI installation or the Sundials source code itself, but rather a problem with how Spack is integrating the dependency.

Potential Causes

• Environment Variables: MPI libraries rely heavily on environment variables to communicate their location and configuration to build processes. If these variables aren't set correctly when Spack initiates the build, Sundials won't be able to find the necessary MPI headers and libraries.
• Module System Conflicts: OpenHPC clusters typically utilize a module system (like lmod or environment-modules) to manage software dependencies. Incorrectly loaded or conflicting modules can lead to build failures. Ensure that the correct MPI module is loaded and that no conflicting modules are interfering.
• Compiler Wrappers: MPI implementations often provide compiler wrappers (e.g., mpicc, mpic++, mpif90) that simplify compiling MPI-aware code. If these wrappers aren't correctly configured or used by Spack, Sundials might not be able to link against the MPI libraries.
• Spack Configuration: Spack has its own configuration and build processes. It's possible that there's an issue with how Spack is configured to handle MPI on your specific OpenHPC cluster. Check your Spack configuration files for any overrides or specific settings related to MPI.

Deep Dive: Troubleshooting Steps

Let's get hands-on. Here's a structured approach to debugging the Sundials build failure:

1. Verify MPI Environment Variables

Before you start, make sure you're in a clean environment where only the necessary modules are loaded. A clean environment ensures you're not inheriting environment variables that might interfere with the build. Check the following:

• MPI Module: Use module avail to list available modules and module load <mpi_module> to load the appropriate MPI module for your cluster (e.g., module load openmpi/4.1.4). Verify that the MPI module is correctly loaded using module list. Make sure you only have one MPI module loaded.
• Environment Variables Inspection: After loading the MPI module, print out all environment variables using the env command. Look for variables related to MPI, such as MPI_HOME, MPICC, MPI_INCLUDE_PATH, MPI_LIB_PATH. These variables should point to the correct locations of your MPI installation. If any of these are missing or incorrect, it's a sign that the MPI module is not setting up the environment properly.
• Compiler Wrappers: Test the compiler wrappers provided by your MPI installation. For example, try compiling a simple