find where lapack and blas exist on hpc

Daniel Parker

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24-02-2025

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Meta Description: Learn how to locate LAPACK and BLAS libraries on your High-Performance Computing (HPC) system. This comprehensive guide covers common locations, environment variables, and troubleshooting tips for efficient scientific computing. Discover how to verify installations and utilize these crucial linear algebra libraries for optimized performance in your HPC applications. (158 characters)

HPC systems often rely on highly optimized linear algebra libraries like LAPACK and BLAS for peak performance in scientific computing. Knowing where these libraries reside on your specific HPC cluster is crucial for successful compilation and execution of your applications. This guide outlines strategies for locating these essential components.

Understanding LAPACK and BLAS

Before diving into the search, let's briefly define these libraries:

• BLAS (Basic Linear Algebra Subprograms): Provides low-level routines for fundamental linear algebra operations, such as vector and matrix multiplication, dot products, and norms. BLAS forms the foundation for many higher-level linear algebra libraries.

• LAPACK (Linear Algebra PACKage): Built upon BLAS, LAPACK provides a broader set of routines for solving linear equations, eigenvalue problems, and singular value decompositions. It handles more complex linear algebra tasks efficiently.

Both libraries are typically highly optimized for specific architectures, leveraging features like vectorization and parallel processing to achieve significant speedups on HPC systems.

Locating LAPACK and BLAS on Your HPC System

Finding LAPACK and BLAS varies depending on your HPC system's configuration. Here's a systematic approach:

1. Check Common Installation Paths

Most HPC systems install these libraries in standard locations. Begin by checking these directories:

• /usr/lib/
• /usr/lib64/ (for 64-bit systems)
• /opt/intel/mkl/ (If using Intel MKL, a popular BLAS/LAPACK implementation)
• /usr/local/lib/
• /sw/lib/ (common in some HPC environments)

Look for files with names like liblapack.so, libblas.so, libmkl_rt.so, etc. The exact filenames might vary slightly based on the specific version and operating system.

2. Utilize Environment Variables

HPC systems often set environment variables pointing to the libraries' locations. Check for variables like:

• LD_LIBRARY_PATH: This variable specifies directories where the dynamic linker searches for shared libraries (.so files).
• LIBRARY_PATH: Similar to LD_LIBRARY_PATH, but might be used in some systems.
• MKLROOT: If Intel MKL is used, this variable indicates the root directory of the MKL installation.

Use the command echo $LD_LIBRARY_PATH (or other relevant environment variables) in your terminal to see their values. The paths listed in these variables should contain the directories where LAPACK and BLAS are located.

3. Use the locate Command

If you're still unsure, use the locate command (requires an updated database):

locate libblas.so
locate liblapack.so

This command searches the entire file system for files matching the specified pattern.

4. Consult Your System's Documentation

Your HPC system's documentation or administrator should provide information about the installed software packages and their locations. Check the system's website, manuals, or contact support if needed.

Verifying the Installation

After locating the libraries, verify they're correctly installed and accessible:

1. Compilation Test: Create a simple C or Fortran program that uses LAPACK or BLAS routines. Attempt to compile it using a compiler (like gfortran or gcc). Successful compilation indicates the libraries are linked correctly.

2. Running a Simple Example: Run a small program utilizing a BLAS or LAPAX function. Successful execution confirms functionality.

Troubleshooting

• Library Not Found: If the compiler can't find the libraries, ensure the correct paths are set in the environment variables (LD_LIBRARY_PATH, LIBRARY_PATH). You may need to add the library directory to these variables using export. Restart your terminal or shell after setting the variables.

• Version Mismatch: Ensure that the compiler and libraries are compatible. Using incompatible versions can lead to errors.

• Permissions Issues: Check if you have the necessary permissions to access the library files.

• Multiple Versions: Some systems may have multiple versions of BLAS and LAPACK installed. Ensure your application links to the correct version.

By systematically applying these steps, you can efficiently locate and verify the installation of LAPACK and BLAS on your HPC system, paving the way for efficient scientific computing. Remember to consult your system's specific documentation for the most accurate and up-to-date information.