yComp

yComp is a Java-based interactive viewer for program dependency graphs and other compiler-related graph structures. It was developed at the IPD Goos group of the Karlsruhe Institute of Technology (KIT), the same research group behind the Firm/libFirm intermediate-representation compiler backend, and it is distributed under an academic yFiles license granted to IPD by yWorks GmbH. Because its rendering and automatic layout are built on yWorks' commercial yFiles library, yComp is licensed strictly for non-commercial use (research, teaching, coursework and application development); commercial use is prohibited. It requires a Java Runtime Environment version 5 or newer and is shipped as a small standalone application (current release 1.3.19).

Its primary input is the VCG format (Visualization of Compiler Graphs) and the closely related GDL (Graph Description Language) text specification originally introduced by the aiSee/VCG tools; the yComp source tree also handles yWorks' own YGF graph format (YGF) and GML (GML). VCG/GDL files are plain-text descriptions listing nodes, edges and rich visual attributes such as colors, shapes, edge classes and nesting into subgraphs, which compilers emit directly when dumping their internal representations. yComp parses these files and applies fully automatic hierarchical layout, so users see a readable arrangement without manual positioning.

The GUI supports panning, zooming and keyboard shortcuts for fast navigation of large graphs, and can export the rendered result to SVG or to PGF/TikZ for direct embedding in LaTeX documents. yComp is best known as the graph viewer bundled with GrGen.NET, a graph-rewriting system whose GrShell drives yComp to visualize and step through host-graph transformations; it plays an analogous debugging role for libFirm, letting compiler developers inspect SSA and dependency graphs during optimization passes.

Within the graph-data and format-conversion landscape yComp is a specialized visualization endpoint rather than a general converter: it consumes the compiler-oriented VCG/GDL family and produces static vector images, not interchange formats. Its strengths are high-quality automatic layout, LaTeX-ready output, and tight integration with compiler and graph-rewriting toolchains. Its limitations are the narrow input scope, the non-commercial license inherited from yFiles, dependence on an aging JRE, and the absence of graph editing or round-trip export; for broader interactive editing or format conversion, tools such as aiSee, yEd or Graphviz cover overlapping niches.