Present CPUs are highly parallel processors with varying levels of parallelism. The typical situation can be described via the following three statements.

• Pursuit of shorter computation time and larger simulation size gives rise to parallel computing.
• Multiple processors are involved to solve a global problem.
• The essence is to divide the entire computation evenly among collaborative processors. Divide and conquer.

Before we proceed with a more detailed discussion of topics like vectorization and parallelization, we need to remind ourselves about some basic features of different hardware models.