Second International UG Workshop 2021

Workshop on Parallel Algorithms in Tree Search and Mathematical Optimization

Date: September 30 - Ocotober 1, 2021
Place: Zuse Institute Berlin, Germany
Organizer: Zuse Institute Berlin


16. February 2021 Announcement of the Second International UG Workshop 2021.

About the UG Workshop

We are happy to announce our upcoming UG Workshop from September 30 to October 1, 2021.

The Ubiquity Generator (UG) is a generic framework for parallelizing branch-and-bound-based solvers. It has been used to create high-performance parallelizations of the mixed-integer programming solver SCIP, CPLEX (deprecated), Xpress, NUOPT, and the two-stage mixed integer stochastic programming solver PIPS-SBB. In the framework, the solvers are abstracted as a base solver. The SCIP Optimization Suite contains the UG parallelizations of SCIP for both shared and distributed memory computing environments, namely FiberSCIP and ParaSCIP.

The capability and flexibility of UG has been demonstrated on several occasions. The biggest computation conducted with ParaSCIP so far has harnessed 80,000 cores on the supercomputer TITAN at Oak Ridge National Laboratory. The results showed the capability of UG to handle up to 80,000 MPI (Message Passing Interface) processes. A UG parallelization of Xpress demonstrated that UG can parallelize multi-threaded base solvers, and the UG parallelization of PIPS-SBB proved that UG can parallelize distributed-memory base solvers. Both solvers have the potential to use over a million CPU cores to solve a single instance in a hybrid parallelization scheme combining UG and base solver parallelization.

The framework architecture allows the parallelization of any branch-and-bound code, but usually requires some extension of the base solver. However, if a parallel solver for a specific problem is developed within the SCIP by adding user-defined plugins, the customized SCIP solver can be parallelized with minimal efforts. Two of the most successful problem-specific parallelizations are SCIP-Jack, a solver for the Steiner tree problem in graphs and its variants, and SCIP-SDP, a solver for mixed-integer semi-definite programming.

This workshop has several goals:

  • showcase current applications of UG,
  • collect feedback from current and potential users on requirements for future features,
  • give hands-on tutorials on how to use the UG framework to parallelize your own branch-and-bound code and how to improve its performance.

More generally, we wish to

  • discuss open questions at the interface of high-performance computing and tree search algorithms, as well as
  • discuss challenges and best practices for sustainably developing, distributing, and maintaining research software.

In this sense, the workshop is also open to a wider audience of researchers and software developers working in this area.


The workshop will be mixed format between online and in-person events. The latter will take place at Zuse Institute Berlin, Takustr 7, 14195 Berlin - Steglitz-Zehlendorf

Accommodation And Travel Information

You can find some travel and accomodation hints on the ZIB Contact page or here (search for districts "Zehlendorf" and "Steglitz" for nearby locations).


The workshop is organized by Yuji Shinano and Franziska Schlösser

Previous Workshop

First International UG Workshop 2019


This research has been supported by the German Research Foundation (DFG) within the project HPO-NAVI:
Nachhaltige Archivierungs- und Veröffentlichungs-Infrastrukturen für High Performance Optimization (ID 391087700).