Parallel calculations

Zebulon has an iterative sub-domain parallel solver which have been proven effective and scalable for non-linear problems. Sub-domains are used in Zebulon, each having a small inverted matrix, and their joint contributions are solved using a conditioned iterative FETI (Finite Element Tearing and Interconnecting) approach. Even on single processor machines, this method has value because it is a good compromise between a full implicit solution with stiffness inverse, and a pure iterative solver (which is likely to diverge in non-linear solutions).

• PVM or MPI interface The parallel solver in Zebulon uses both standard interfaces for interprocess communication. These interfaces abstract the hardware or machine dependent issues so the calcul ation can run in particularly inhomogeneous environments. This means that a single processor machine can act like a multiprocessor machine, and a network of dissimilar computers (even remotely located) can be used as a parallel computer.
• Advanced solver The solver uses a preconditioned multi-domain FETI solver to handle the parallel matrix inversion. Tools are provided to automatically divide a mesh into well shaped, uniform size domains. This solver has been proven effective for strongly non-linear problems in viscoplasticity with thermal loading cycles.

• Scalability The nature of the domain method with a FETI solver gives reduced message passing requirements between processes, which is normally the limiting factor for large scale parallelism. The method therefore remains efficient up to several dozen processors.
• Local level parallelism For problems where the material law integration is more costly than the global solution (small meshes with a very large number of state variables) parallel calculations can be applied to the local integration. This has allowed interesting results using even separate finite element models for each Gauss point in a structure (FE inside FE)!