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## LAPACK

As mentioned before, LAPACK, or Linear Algebra PACKage [3], is a collection of routines for solving linear systems, least squares problems, eigenproblems, and singular problems. High performance is attained by using algorithms that do most of their work in calls to the BLAS, with an emphasis on matrix-matrix multiplication. Each routine has one or more performance tuning parameters, such as the sizes of the blocks operated on by the BLAS. These parameters are machine dependent and are obtained from a table defined when the package is installed and referenced at runtime.

The LAPACK routines are written as a single thread of execution. LAPACK can accommodate shared-memory machines, provided parallel BLAS are available (in other words, the only parallelism is implicit in calls to BLAS). Extensive performance results for LAPACK can be found in the LAPACK Users' Guide [3].