Part of the DynGraphLab — Dynamic Graph Algorithms open source framework. Developed at the Algorithm Engineering Group, Heidelberg University.

Python Interface: An easy-to-use Python interface for this software is available in CHSZLabLib.

This repository implements and benchmarks state-of-the-art and new approaches for finding optimal as well as good delta-orientations in sparse graphs. The objective is to maintain an orientation of the edges in an undirected graph such that the maximum out-degree of any vertex remains low. When edges are inserted or deleted, it may be necessary to reorient some edges to prevent vertices from having excessively high out-degrees.

The repository contains two types of algorithms — exact algorithms and heuristics:

• The best heuristic algorithm, based on breadth-first search, computes the optimum result on more than 90% of instances and is on average only 2.4% worse than the optimum solution.
• The exact algorithm maintains an optimal edge orientation during both insertions and deletions, with update times up to 6 orders of magnitude faster than static exact algorithms.

For optimal static algorithms, see HeiOrient.

brew install DynGraphLab/dyngraphlab/dyndeltaorientation

Then run:

dyndeltaorientation FILE --algorithm=IMPROVEDOPT

git clone https://github.com/DynGraphLab/DynDeltaOrientation
cd DynDeltaOrientation
./compile_withcmake.sh -DILP=Off

All binaries are placed in ./deploy/. To enable ILP-based algorithms (requires Gurobi):

./compile_withcmake.sh -DILP=On

Alternatively, use the standard CMake process:

mkdir build && cd build
cmake ../ -DCMAKE_BUILD_TYPE=Release -DILP=Off
make && cd ..

dyndeltaorientation FILE [options]

./deploy/delta-orientations examples/youtube-u-growth.seq --algorithm=IMPROVEDOPT
./deploy/delta-orientations examples/youtube-u-growth.seq --algorithm=NAIVE
./deploy/delta-orientations examples/youtube-u-growth.seq --algorithm=MAXDECENDING --depth=10
./deploy/delta-orientations examples/youtube-u-growth.seq --algorithm=KFLIPS --flips=10

For all available algorithms and options:

./deploy/delta-orientations --help

Dynamic graph sequence format. The first line starts with # followed by the number of nodes and updates. Each subsequent line specifies an operation: 1 u v for edge insertion, 0 u v for edge deletion.

# 30399 87627
1 1 2
1 51 52
0 1 2

The program is licensed under the MIT License. If you publish results using our algorithms, please acknowledge our work by citing the following papers.

When using the heuristic algorithms:

@inproceedings{DBLP:conf/acda/BorowitzG023,
  author       = {Jannick Borowitz and
                  Ernestine Gro{\ss}mann and
                  Christian Schulz},
  title        = {Engineering Fully Dynamic {\(\Delta\)}-Orientation Algorithms},
  booktitle    = {{SIAM} Conference on Applied and Computational Discrete Algorithms,
                  {ACDA} 2023},
  pages        = {25--37},
  publisher    = {{SIAM}},
  year         = {2023},
  doi          = {10.1137/1.9781611977714.3}
}

When using the exact algorithms:

@inproceedings{DBLP:conf/alenex/GrossmannR0W25,
  author       = {Ernestine Gro{\ss}mann and
                  Henrik Reinst{\"{a}}dtler and
                  Christian Schulz and
                  Fabian Walliser},
  title        = {Engineering Fully Dynamic Exact {\(\Delta\)}-Orientation Algorithms},
  booktitle    = {27th Symposium on Algorithm Engineering and Experiments,
                  {ALENEX} 2025},
  pages        = {15--28},
  publisher    = {{SIAM}},
  year         = {2025},
  doi          = {10.1137/1.9781611978339.2}
}