High Performance Computing

For what purpose

High-performance computing is concerned with the use of parallel programs on compute clusters. A cluster is a set of computers that are connected together and configured so as to appear as a single, large, machine. It is used for large-scale scientific computations.

For whom

A typical desktop workstation is able to perform several dozens billion floating-point arithmetic operations per seconds, while a typical cluster as we are discussing here can do 200 to 300 times more operations per seconds. That compute power lies in the large number of CPUs present in the cluster, but also in the large memories (10 times to 20 times the memory of a typical workstation) and very fast interconnect (100 to 1000 times the office connection.) While the computing power is enormous, not every program/application can benefit of it ; only parallel programs, that use several CPUs at the same time, can run fast on clusters. Serial programs, that only use one CPU at a time, will not benefit from clusters, and might even run slower on a cluster than on a recent high-end laptop.


On the university campus, we operate two clusters :

  • Lemaitre3, dedicated to large parallel jobs (HPC), with a fast interconnect and a fast storage system;
  • Manneback, dedicated to High-Throughput Computing (HTC) and specific hardware such as GPU, suited for running a very large number of small jobs;

As we are part of CÉCI, the "Consortium des Équipements de Calcul Intensif", any user who is granted access to our compute clusters automatically also has access to all the CÉCI clusters. Read more on the CÉCI clusters...

Members of UCLouvain (intranet) can see the graphs of the load of the three clusters for the last 30 days and the cpu-hours spent by all UCLouvain groups (poles).


Access to the compute clusters is offered to any UCLouvain-affiliated researcher or student whose needs in computations grow beyond what a single workstation can offer, be it for numerical simulation, optimization, number crunching, etc. Our biggest users include for instance NAPS, for ab initio computations of chemical interactions, and TFL for computer simulations of physical models. Read more on how to request access...

Once the user is granted access, he or she is given a private SSH key that allows him/her connecting to the cluster of his/her choice, and transferring data back and forth. Read more on how to connect to the clusters...


Usage is mostly free, except for specific circumstances. Read more about the costs....