LINPACK is a computer benchmark used to rank supercomputers, most notably for the well recognized "TOP500" list maintained by the University of Mannheim and the University of Tennessee.
Originally devised and designed by Jack Dongarra, LINPACK consists of a highly parallel algorithm for solving a system of linear equations. It is recognized as being a good representation of a given computer's dedicated processing power for solving the typical problems that are run on supercomputers -- namely, simultaneously solving numerous equations with floating point values.
For more info:
http://www.netlib.org/benchmark/performance.ps (a VERY long report by Dongarra)