CMake Error: MPI_LIBRARY not found - How to Fix

This error message indicates that the CMake configuration for your project expects the variable 'MPI_LIBRARY' to be set, but it's currently set to 'NOTFOUND'. This means CMake couldn't find the MPI library.

Here's how to fix this error:

1. Verify MPI Installation: Ensure you have MPI (Message Passing Interface) installed on your system. It's crucial for parallel computing and often used in scientific and engineering applications.

2. Check MPI Library Location: If MPI is installed, confirm it's not in a non-standard location. If it is, you'll need to tell CMake its specific path.

3. Install MPI: If you haven't installed MPI, you'll need to do so before proceeding. Installation steps vary depending on your operating system.

   • Linux: Typically, you can install MPI using your package manager (e.g., 'apt' or 'yum').
   • Windows: Use a distribution like MS-MPI or MPICH.

4. Set the MPI_LIBRARY Variable: Once MPI is installed, you need to set the 'MPI_LIBRARY' variable within your CMake files. You can do this by:

   • Modifying CMakeLists.txt: Edit the file directly to specify the path to the MPI library.
   • Command-line Argument: Pass the variable as an argument to CMake during build file generation. For example:

   cmake -DMPI_LIBRARY=/path/to/mpi/library ..  
   

   Replace '/path/to/mpi/library' with the actual path on your system.

5. Regenerate Build Files: After setting 'MPI_LIBRARY', run CMake again to regenerate the build files. The error should be resolved if the MPI library is found correctly.

If you're still encountering issues, consult the project's documentation or seek help from the project's developers or community.