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1 This package provides library(callgraph), a tool for compiling a graph of calls between predicates in a module.
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2
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3 ---++++ Prerequisites
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4
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5 The graph layout programs from the GraphViz library (http://graphviz.org/) are
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6 used to render the end result. Whilst you can produce a dot file without them,
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7 you will need them for the final rendering.
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8 On Mac OS X with MacPorts installed, do this at the bash prompt.
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9 ==
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10 $ sudo port install graphviz
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11 ==
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12 On Debian based systems, do this:
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13 ==
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14 $ sudo apt-get install graphviz
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15 ==
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16 And so on.
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17 You will need a PDF viewer to see the results.
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18
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19
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20
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21 ---++++ Simple usage
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22
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23 To produce a call graph as a PDF, make sure that both this module and the
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24 module you wish to analyse are loaded, then do this:
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25 ==
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26 ?- module_dotpdf(<module_name>,[]).
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27 ==
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28 This will produce a PDF file <module_name>.pdf in the current directory.
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29 Often, the default layout program, dot, will produce a very wide graph.
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30 This can sometimes be alleviated by using the unflatten program from the
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31 Graphviz tools. In module_dotpdf/2, the default layout method does actually
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32 use unflatten without any parameters, but if this is not enough, you can
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33 provide values for the -f, -l and -c switches of unflatten (see the man
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34 page for unflatten for more details). For example, to produce a graph of
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35 callgraph itself, you can try the following:
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36 ==
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37 $ swipl
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38 ?- use_module(library(callgraph)).
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39 ?- module_dotpdf(callgraph,[method(unflatten([fl(4),c(4)]))]).
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40 ==
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41
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42 ---++++ Output formats
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43
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44 If you want the dot language source file, use module_dot/2 instead. The
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45 method option is then inapplicable.
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46
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47 The code can also produce rendered graphs in any format supported by
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48 Graphviz, but this functionality is not currently exposed.
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49
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50 ---++++ Limitations
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51
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52 The graph compilation relies on prolog_walk_code/1 to do the actual code
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53 analysis. This does a good job in most cases, using meta-predicate declarations
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54 or inferred meta-predicates to detect many high-order calling patterns.
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55 Ironically enough, callgraph fails to analyse itself fully because
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56 prolog_walk_code/1 does not detect that it itself calls a given predicate
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57 for each call detected. Thus, in the example, there is no edge from
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58 assert_module_graph/1 to assert_edge/4.
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59
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60 ---++++ Planned enhancements
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61
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62 The main thing to add next is to render graphs for multiple modules using dot's
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63 subgraph facility. Otherwise, the system for dealing with style attributes is
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64 a bit messy and could be cleaned up.
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