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NESL

Language type:

P - Parallel or Multi-programming

Description:

NESL is a data-parallel functional programming language intended to be highly portable across different parallel computer architectures, easy to use, and efficient to compile.
The basic data types supported by NESL are: integers, reals, strings, and sequences (vectors). The sequences are heavily used for defining parallelism, NESL has special operators and syntax for operating on all elements of a sequence and on each element of a vector. In addition to its parallel computation constructs, NESL also supports conventional selection (if-then-else) and iteration (for, while) control-flow constructs.
The NESL function library provides a rich set of sequence operations, plus string manipulation, I/O, system interface, and windowing functions. Currently, NESL runs only on UNIX and related systems (or parallel computers attached to such systems); its windowing support is currently implemented only for X11.
NESL is usually compiled; the compilation process automatically generates a mapping from the computation defined by the NESL code onto the processors of the target computer. Variables and functions in NESL are not strongly typed, but the compiler seems to perform extensive type inference at compile-time. Releases 3.1 and later of NESL also include a lightweight interpreter for use in training and debugging. The NESL compiler is written in C, and the interpreter is implemented in Common Lisp.
Implementations of NESL are available from CMU. The documentation and a tutorial are also available on the web.

Origin:

Guy Blelloch, Carnegie-Mellon, 1992-93

See Also:

ML    Lucid    Clean   

Remarks:

NESL is a project of SCandAL group at CMU. They are working on porting the language to a variety of parallel architectures. They also have a system for translating NESL programs into multi-threaded Java programs.
NESL has special features for animating the execution of parallel algorithms, a helpful feature for presenting papers at conferences and for computer science education. Some live animations can be seen at the NESL pages at CMU.
NESL has been the experimental vehicle for research in provable performance bounds in parallel algorithms, as well as parallel-processing compiler research.

Links:

Interactive Interface to NESL

NESL distribution download site

Date:

Last updated 12/23/97

Sample code:

% Fits a line to a set of of points  %
% using a simple regression algorithm, %
% return line and goodness of fit.   %
% (from code examples with NESL 3.1) %
function line_fit(x, y) =
let 
  n    = float(#x);
  xa   = sum(x)/n;
  ya   = sum(y)/n;
  Stt  = sum({(x - xa)^2: x});
  b    = sum({(x - xa)*y: x; y})/Stt;
  a    = ya - xa*b;
  chi2 = sum({(y-a-b*x)^2: x; y});
  siga = sqrt((1.0/n + xa^2/Stt)*chi2/n);
  sigb = sqrt((1.0/Stt)*chi2/n)
in 
  (a, b, siga, sigb) $

Descriptions in this dictionary are ©1997-99 Neal Ziring. Some examples copyright of their respective authors. Some technologies and languages are trademarked. Permission to copy descriptions is granted as long as authorship credit is preserved.

Comments on this dictionary, corrections and suggestions, are all welcome. Please use email, the address is ziring@home.com