Solving a large model with millions of DOFs or a medium-sized model with nonlinearities that needs many iterations to reach convergence can require many CPU hours. To decrease simulation time, Ansys, Inc. offers different parallel processing options that increase the model-solving power of Ansys products by using multiple processors (also known as CPU cores). The following parallel processing capabilities are available:

Multicore processors, and thus the ability to use parallel processing, are now widely available on all computer systems, from laptops to high-end servers. The benefits of parallel processing are compelling but are also among the most misunderstood. This chapter explains the types of parallel processing available in Ansys and also discusses the use of GPUs (considered a form of shared-memory parallel processing) and how they can further accelerate the time to solution.

Currently, the default scheme is to use four cores with distributed-memory parallelism. For many of the computations involved in a simulation, the speedups obtained from parallel processing are nearly linear as the number of cores is increased, making very effective use of parallel processing. However, the total benefit (measured by elapsed time) is problem dependent and is influenced by many different factors.

No matter what form of parallel processing is used, the maximum benefit attained will always be limited by the amount of work in the code that cannot be parallelized. If just 20 percent of the runtime is spent in nonparallel code, the maximum theoretical speedup is only 5X, assuming the time spent in parallel code is reduced to zero. However, parallel processing is still an essential component of any HPC system; by reducing wall clock elapsed time, it provides significant value when performing simulations.

Distributed-memory parallel (DMP) processing, shared-memory parallel (SMP) processing, hybrid parallel processing, and GPU acceleration can require HPC licenses. You can use up to four CPU cores or a combination of four CPUs and GPUs without using any HPC licenses. Additional licenses will be needed to run with more than four. See HPC Licensing for more information.