************ Synthetic traffic with dragonfly network model **********
- traffic patterns supported: uniform random and nearest neighbor traffic.
- Uniform random traffic: sends messages to a randomly selected destination node. It is uniformly distributed throughout the network and gives a better performance with minimal routing and therefore higher simulation event rate.
- Nearest neighbor traffic: with minimal routing, it sends traffic to the single global channel connecting two groups (it congests the network when using minimal routing). May have a low simulation event rate because of the congestion being simulated.
arrival_time: inter-arrival time between the messages. Smaller inter-arrival time means messages will arrive more frequently (smaller inter-arrival time can cause congestion in the network and may overflow the network buffers).
traffic: 1 for uniform random traffic, 2 for nearest neighbor traffic.