Editing Load balancing (computing) (section)

===Static and dynamic algorithms===

====Static====
A load balancing algorithm is "static" when it does not take into account the state of the system for the distribution of tasks. Thereby, the system state includes measures such as the [[Load (computing)|load level]] (and sometimes even overload) of certain processors. Instead, assumptions about the overall system are made beforehand, such as the arrival times and resource requirements of incoming tasks. In addition, the number of processors, their respective power and communication speeds are known. Therefore, static load balancing aims to associate a known set of tasks with the available processors in order to minimize a certain performance function. The trick lies in the concept of this performance function.

Static load balancing techniques are commonly centralized around a router, or [[Master/slave (technology)|Master]], which distributes the loads and optimizes the performance function. This minimization can take into account information related to the tasks to be distributed, and derive an expected execution time.

The advantage of static algorithms is that they are easy to set up and extremely efficient in the case of fairly regular tasks (such as processing [[HTTP]] requests from a website). However, there is still some statistical variance in the assignment of tasks which can lead to the overloading of some computing units.

====Dynamic====
Unlike static load distribution algorithms, dynamic algorithms take into account the current load of each of the computing units (also called nodes) in the system. In this approach, tasks can be moved dynamically from an overloaded node to an underloaded node in order to receive faster processing. While these algorithms are much more complicated to design, they can produce excellent results, in particular, when the execution time varies greatly from one task to another.

Dynamic load balancing architecture can be more [[Modular design|modular]] since it is not mandatory to have a specific node dedicated to the distribution of work. When tasks are uniquely assigned to a processor according to their state at a given moment, it is a unique assignment. If, on the other hand, the tasks can be permanently redistributed according to the state of the system and its evolution, this is called dynamic assignment.<ref>{{cite journal |last1=Alakeel |first1=Ali |title=A Guide to Dynamic Load Balancing in Distributed Computer Systems |journal=International Journal of Computer Science and Network Security  |date=November 2009 |volume=10 |url=https://www.researchgate.net/publication/268200851}}</ref> Obviously, a load balancing algorithm that requires too much communication in order to reach its decisions runs the risk of slowing down the resolution of the overall problem.