NAS
A Revision of the NASA Kernel Benchmark Program

NAS is a C++ program which is a revision of David Bailey's NASA kernel benchmark program.

The NAS benchmark program was developed around 1984, and measured computational performance on a representative range of realistic calculations. One motivation for this benchmark was to move beyond the LINPACK benchmark, which focussed on a single highly structured procedure.

Benchmarking computers has become much more difficult now that memory, I/O, multicores and distributed memory have all become significant factors in computing performance. Nonetheless, the NAS benchmarks provide an interesting insight into the floating point processing power of a system, and so, for this reason, a version of the program has been created that retains the functionality of the original, while being somewhat easier to transfer to other languages.

One might expect comparable numerical performance of C++ and FORTRAN programs. That this does not seem to happen for the C++ and FORTRAN90 versions of NAS reflects, most likely, the fact that the C++ version was "translated" in a fairly straightforward manner, resulting in some awkward and inefficient expressions; in particular, FORTRAN arrays which were multiply-indexed were implemented in C++ as vectors, with the resulting overhead of computing indices explicitly. Thus, it is likely that a more careful revision of the C++ source code would result in substantial performance improvements. I, on the other hand, am simply terribly relieved that the C++ program gets the right answers.

Usage:

nas

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages:

NAS is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

LINPACK_BENCH, a C++ program which measures the time taken by LINPACK to solve a particular linear system.

MATMUL, a C program which is an interactive matrix multiplication benchmark.

MDBNCH, a FORTRAN77 program which is a benchmark molecular simulation calculation.

Reference:

1. David Bailey, John Barton,
   The NAS Kernel Benchmark Program,
   Numerical Aerodynamics Simulations Systems Division,
   NASA Ames Research Center,
   13 June 1986.

Source Code:

• nas.cpp, the source code.
• nas.sh, BASH commands to compile the source code.

Examples and Tests:

• nas_output.txt, the output file.

List of Routines:

• MAIN is the main program for NAS.
• MXMTST is the test program for MXM.
• MXM computes the matrix product C = A * B.
• FFTTST is the test program for CFFT2D1 and CFFTD2.
• CFFT2D1 performs complex radix 2 FFT''s on the first dimension.
• CFFT2D2 performs complex radix 2 FFT''s on the second dimension.
• CHOTST is the test program for CHOLSKY.
• CHOLSKY carries out Cholesky decomposition and back substitution.
• BTRTST is the test program for BTRIX.
• BTRIX is a block tridiagonal solver in one direction.
• GMTTST is the test program for GMTRY.
• GMTRY computes solid-related arrays.
• EMITST is the test program for EMIT.
• EMIT creates new vortices according to certain boundary conditions.
• VPETST is the test program for VPENTA.
• VPENTA inverts 3 pentadiagonal systems simultaneously.
• I4_MAX returns the maximum of two I4's.
• I4_MIN returns the smaller of two I4's.
• R8_ABS returns the absolute value of an R8.
• R8_MAX returns the maximum of two R8's.
• R8_MIN returns the minimum of two R8's.
• R8VEC_COPY copies an R8VEC.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• WTIME reports the elapsed wallclock time.

You can go up one level to the C++ source codes.