NBench
Encyclopedia
NBench is a synthetic computing benchmark
program developed in the mid 1990s by the now defunct BYTE magazine
intended to measure a computer's CPU, FPU, and Memory System
speed.
, and was initially focused on PCs running the Microsoft Windows operating system. Independently of BYTE, in 1996 NBench was ported to Linux
and other flavors of Unix
by Uwe F. Mayer.
More recently Ludovic Drolez prepared an NBench App for the Android mobile device operating system.
NBench should not be confused with the similarly named but unrelated AMD N-Bench.
A run of the benchmark suite consists essentially of two phases for each of the tests. First, a calibration loop is run to determine the size of the problem the system can handle in a reasonable time, in order to adapt to the ever faster computer hardware available. Second, the actual test is run repeatedly several times to obtain a statistically meaningful result.
Originally, NBench and BYTEmark produced two overall index figures: Integer index and Floating-point index. The Integer index is the geometric mean of those tests that involve only integer processing—numeric sort, string sort, bitfield, emulated floating-point, assignment, Huffman, and IDEA—while the Floating-point index is the geometric mean of those tests that require the floating-point coprocessor—Fourier, neural net, and LU decomposition. The index figures where relative scores to get a general feel for the performance of the machine under test as compared to a baseline system based on a 90 MHz Pentium Intel CPU.
The Linux/Unix port has a second baseline machine, it is an AMD K6/233 with 32 MB RAM and 512 KB L2-cache running Linux 2.0.32 and using GNU gcc version 2.7.2.3 and libc-5.4.38. The original integer index was split into an integer-operation and a memory-operation index, as suggested by Andrew D. Balsa, reflecting the realization that memory management is important in CPU design. The original tests have been left alone, however, the geometric mean of the tests numeric sort, floating-point emulation, IDEA, and Huffman now constitutes the integer-arithmetic focused benchmark index, while the geometric mean of the tests string sort, bitfield, and assignment makes up the new memory index. The floating point index has been left alone, it is still the geometric mean of fourier, neural net, and LU decomposition.
), and on also on Macs (it is in particular available as a Darwin
port).
A results page from runs on many different hardware configurations, from high powered multi-CPU servers down to low-powered network switches, is maintained by the original porter.
Benchmark (computing)
In computing, a benchmark is the act of running a computer program, a set of programs, or other operations, in order to assess the relative performance of an object, normally by running a number of standard tests and trials against it...
program developed in the mid 1990s by the now defunct BYTE magazine
Byte (magazine)
BYTE magazine was a microcomputer magazine, influential in the late 1970s and throughout the 1980s because of its wide-ranging editorial coverage...
intended to measure a computer's CPU, FPU, and Memory System
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
speed.
History
NBench is essentially release 2 of BYTE Magazine's BYTEmark benchmark program (previously known as BYTE's Native Mode Benchmarks), published about 1995, which was just a few years before the magazine ceased publication. NBench is written in CC (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, and was initially focused on PCs running the Microsoft Windows operating system. Independently of BYTE, in 1996 NBench was ported to Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
and other flavors of Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
by Uwe F. Mayer.
More recently Ludovic Drolez prepared an NBench App for the Android mobile device operating system.
NBench should not be confused with the similarly named but unrelated AMD N-Bench.
Design
The NBench algorithm suite consists of ten different tasks:- Numeric sort - Sorts an array of long integers.
- String sort - Sorts an array of strings of arbitrary length.
- Bitfield - Executes a variety of bit manipulation functions.
- Emulated floating-point - A small software floating-point package.
- Fourier coefficients - A numerical analysis routine for calculating series approximations of waveforms.
- Assignment algorithm - A well-known task allocation algorithm.
- Huffman compression - A well-known text and graphics compression algorithm.
- IDEA encryption - A relatively new block cipher algorithm.
- Neural Net - A small but functional back-propagation network simulator.
- LU Decomposition - A robust algorithm for solving linear equations.
A run of the benchmark suite consists essentially of two phases for each of the tests. First, a calibration loop is run to determine the size of the problem the system can handle in a reasonable time, in order to adapt to the ever faster computer hardware available. Second, the actual test is run repeatedly several times to obtain a statistically meaningful result.
Originally, NBench and BYTEmark produced two overall index figures: Integer index and Floating-point index. The Integer index is the geometric mean of those tests that involve only integer processing—numeric sort, string sort, bitfield, emulated floating-point, assignment, Huffman, and IDEA—while the Floating-point index is the geometric mean of those tests that require the floating-point coprocessor—Fourier, neural net, and LU decomposition. The index figures where relative scores to get a general feel for the performance of the machine under test as compared to a baseline system based on a 90 MHz Pentium Intel CPU.
The Linux/Unix port has a second baseline machine, it is an AMD K6/233 with 32 MB RAM and 512 KB L2-cache running Linux 2.0.32 and using GNU gcc version 2.7.2.3 and libc-5.4.38. The original integer index was split into an integer-operation and a memory-operation index, as suggested by Andrew D. Balsa, reflecting the realization that memory management is important in CPU design. The original tests have been left alone, however, the geometric mean of the tests numeric sort, floating-point emulation, IDEA, and Huffman now constitutes the integer-arithmetic focused benchmark index, while the geometric mean of the tests string sort, bitfield, and assignment makes up the new memory index. The floating point index has been left alone, it is still the geometric mean of fourier, neural net, and LU decomposition.
Use
The benchmark suite has seen consistent use since the mid 1990s by the personal computing community, on PCs and other devices running various flavors of UNIX including Linux or BSD, or running Windows (usually in combination with CygwinCygwin
Cygwin is a Unix-like environment and command-line interface for Microsoft Windows. Cygwin provides native integration of Windows-based applications, data, and other system resources with applications, software tools, and data of the Unix-like environment...
), and on also on Macs (it is in particular available as a Darwin
Darwin (operating system)
Darwin is an open source POSIX-compliant computer operating system released by Apple Inc. in 2000. It is composed of code developed by Apple, as well as code derived from NeXTSTEP, BSD, and other free software projects....
port).
A results page from runs on many different hardware configurations, from high powered multi-CPU servers down to low-powered network switches, is maintained by the original porter.
Shortcomings
Using NBench as a benchmark has pitfalls:- These benchmarks are meant to expose the theoretical upper limit of the CPU, FPU, and memory architecture of a system. They cannot measure video, disk, or network throughput (those are the domains of a different set of benchmarks).
- NBench is single-threaded. Currently, each benchmark test uses only a single execution thread. However, most modern operating systems have some multitasking component. How a system "scales" as more tasks are run simultaneously is an effect that NBench does not explore.