.. highlight:: c++
  :linenothreshold: 5

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Module 4: OpenMP Case Study: N-body problem
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The problem
===========
Simulate the motion of stars, planets, etc.

Math
====
Divide time to small sections. Calculate physical variables at every time stop
progressively.

Serial Solution
===============
Two layer of nested loops. One outer loop and multiple inner loops. Data
dependency exists between loops in the inner layer.

OpenMP Optimization
===================
+ Optimize inner layer loops
+ Use ``#pragma omp parallel`` on outer loop to pre-fork threads
+ Use ``#pragma omp for`` on inner layers
+ Barriers and critical sections