Module One

At Cardiff work has been completed on linking simple nCUBE2 C programs into the Xmosaic hypertext environment on SUN workstations. This simple introductory module, which uses an nCUBE2 multicomputer, has the objectives of

1. familiarizing undergraduates with the Xmosaic environment,
2. instructing them in the communications routines used on the nCUBE2 computer for message passing,
3. introducing the students to the concept of distributed memory parallel computers and the need for message passing.

Both graphics and text are used in the modules to aid students understanding of various concepts, for example, Figure 1 is one of several diagrams used to explain message passing and the presence of local memory in individual processors.

Two example programs are provided in the module to illustrate the use of the communication routines to pass data around the processors in some specified manner. Figure 2 contains the user screen for describing the two example programs with links for viewing the C source code and for running the programs on the nCUBE 2 to show program output.

In order to run programs and also to list program source code we usually embed programs in a UNIX script. This is so that formatting of the output can be controlled. For this reason we favour PERL scripts although any UNIX scripts (i.e. C and Bourne shells) could be used.

Links to program source and executable code is achieved by running a PERL script in one of two ways:

Embedding program listing in HTML output

- the (standard) output of the PERL script is HTML code it may include titles, headers etc. but must include an HTML flag to embed the listed code in a preformatted command (<pre>...</pre>).

The browser being instructed to recognise raw text

- If the first line of a file (or standard output from a script) includes the line Content-type: text/html then all following text is treated as being straight ASCII text.

The hypertext link in the HTML file is a path to the executable shell (or program) just as if it were a HTML file.