![]() ![]() I also discovered that gnuplot allows user-defined variables to be declared, and supports mathematical operations on them. Fortunately, I recalled that a computer is good at this sort of thing (the clue is in the name, after all). And I was getting tired of keeping track of the running number of objects, and working out in my head the locations of the boundaries. So I started writing the script in this fashion:īut I hadn't got very far before realising that hardwiring all of the coordinate values wasn't a good idea if - say - the size of the boxes, or the spacing between them, needed changing. However, the elementary components aren't hard to find: thus, gnuplot has aset object rectangle command which creates a rectangle, given the coordinates of its diagonal corners, a set arrow command which creates an arrow (or a line) between two endpoints, and a set label command which adds text at a specified location. Whilst producing this sort of picture in gnuplot is comparatively straightforward, and can be done with a handful of commands, the diagram in Figure 1 presents a few more challenges. We use the program a lot for the display of the results from the example programs which form an important part of NAG Library documentation thus, Figure 2 is a plot of the output from the c06ab routine, which is used in the numerical summation of series.įigure 2. Several example scripts (and their associated output) are available at the gnuplot site - for example, these illustrate the range of the program's functionality for plotting analytical functions. the user either enters commands one at a time at its interactive prompt, or puts the commands into a script, which the program then loads and runs. Gnuplot's interface is command-driven - i.e. It runs on a variety of platforms, and is freely distributed. The request was to reproduce the figure using gnuplot, a plotting program that can be used to create a wide variety of two- and three-dimensional plots of data, functions and approximations to data. Data distribution across a grid of processors More specifically, this example shows the distribution of a two-dimensional matrix consisting of twelve rows and columns (each numbered from 1 to 12) across a two by three grid of processors.įigure 1. It's a schematic illustration of the way in which, for certain routines in the Library, elements of a matrix are distributed between compute processors. ![]() I received the latest of these queries last week, from a colleague who wanted to reproduce Figure 1 (below) as part of the documentation for the NAG Parallel Library. Accordingly, every now and again I get contacted by one of my colleagues who needs to draw a graph, or reformat an image, or incorporate a visualisation into a document, and is - usually - too busy with other (probably more important) activities to spend a lot of time figuring out how to make a graphics package behave itself and do the right thing. One of the side effects of having the word 'visualisation' in your job title is that people expect you to know something about the subject. Fortran Library for SMP & Multicore Versions.Software Optimization and Code Modernization. ![]()
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