# Overview+
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+
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The Ideal Graph Visualizer is a tool developed to help examine the intermediate+
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representation of C2 which is commonly referred to as the "ideal graph". It was+
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developed in collaboration with the University of Linz in Austria and has been+
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included as part of hotspot since that was the primary target of the tool. The+
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tool itself is fairly general with only a few modules that contain C2 specific+
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elements.+
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The tool is built on top of the NetBeans 7 rich client infrastructure and so+
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requires NetBeans to build. It currently requires at least Java 6 to run as it+
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needs support for JavaScript for its filtering mechanism and assumes it's built+
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into the platform.  It should build out of the box with NetBeans 7.0 and Java 6+
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or later.+
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# Building and Running+
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The build system used for IGV is ant. To download all required libraries and+
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build IGV, issue `ant build`. To run IGV, use the `igv.sh` command; it will put+
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all log messages generated by the run to the file `.igv.log`. To see all log+
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messages generated during an IGV run, use `ant run`.+
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# Usage+
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The JVM support is controlled by the flag `-XX:PrintIdealGraphLevel=#` where `#`+
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is:+
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* 0: no output, the default+
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* 1: dumps graph after parsing, before matching, and final code (also dumps+
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     graphs for failed compilations, if available)+
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* 2: more detail, including after loop opts+
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* 3: even more detail+
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* 4: prints graph after parsing every bytecode (very slow)+
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By default the JVM expects that it will connect to a visualizer on the local+
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host on port 4444. This can be configured using the options+
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`-XX:PrintIdealGraphAddress=` and `-XX:PrintIdealGraphPort=`.+
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`PrintIdealGraphAddress` can actually be a hostname.+
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It is advisable to run the JVM with background compilation disabled (-Xbatch).+
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Compilations going on in the background may be cancelled when the VM terminates,+
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which can lead to incomplete dumps being sent to IGV.+
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Alternatively the output can be sent to a file using+
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`-XX:PrintIdealGraphFile=filename`. Each compiler thread will get it's own file+
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with unique names being generated by adding a number onto the provided file+
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name.+
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+
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More information about the tool is available at+
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https://wiki.openjdk.java.net/display/HotSpot/IdealGraphVisualizer.+
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