A Linear Solver for the Exascale Era

What is GaspiLS?

GaspiLS is a scalable linear solver library for the exascale age and is industry proven in CFD and FEM simulations. Its easily extendable standard API is compact, yet powerful for parallel computations and allows for smooth transitions from legacy applications in little to no time.

GaspiLS comes with a collection of iterative solvers (Richardson, (P)CG, BiPCGStab, GMRES) and preconditiones (Jacobi, ILU(0), MILU), which can be easily expanded by adding custom solvers and/or preconditioners.

A hybrid-parallel implementation for scalability results in a much better surface to volume ratio and the task based parallelization yields optimal load balancing. The design is multi-threaded with thread-safe matrix assembly and fully threaded matrix finalization.

GaspiLS inherits the Gaspi/GPI-2 programming model and leverages its unique advantages to achieve overlap of computation and communication.

Overlapping of computation and communication

GaspiLS is open-source GPLv3. Download and try it out now!

Performance & Scalability

The need for scalability is driven by the hardware trend of increased parallelism.

Scalability quantifies the additional benefit generated by adding extra resources to a computational problem. In case of optimal scalability, this benefit is 100 percent and only optimal scalability can guarantee full resource utilization. GaspiLS delivers superior performance and scalability, which means:

  • Time to solution can be practically reduced as much as required by adding extra resources.
  • There is pratically no limit on the modelling complexity and its enormous memory footprint, as memory is simply accumulated across nodes.
  • There is no need for expensive resources. Instead of high-end fat nodes, use a bunch of cheap commodity hardware nodes.
  • Optimal energy efficiency because hardware is used to capacity and never sits around being idle.

Jacobi preconditioned Richardson, 3D Poission equatoin (2nd order FD discretization), cubic grid (359³)


GaspiLS achieves its superior scalability and performance by striving for 100 percent resource utilization.

Explicit distinction between local and remote entries within a single matrix row allows to optimize overlap of local compute and communication of remote vector entries.

Dynamic load balancing avoids idle resources

Overlapping of computation and communication avoids aggregation of communication latencies.

Removing synchronization points wherever possible prevents aggregation of imbalances.

A hybrid-parallel implementation speeds up collective operations and reduces the inter-process communication overhead.


Don't take it from us, take it from those who are using GaspiLS already.


GaspiLS has received funding from the European Union’s Horizon 2020 research and innovation programme in the scope of the HYSCALA project under the grant agreement No 800881.