Definition
Centralised Algorithm ( Distributed System)
A centralised algorithm computes decisions for a distributed system at a central decision point, using information about the state of the participating components.
When decisions require complete system-wide information, collecting, storing and updating that information adds cost as the system grows. The central computation and its communication load can become bottlenecks even when the participating components have spare capacity.
A decentralised algorithm instead distributes decision-making among the participants.
Example
Routing from Complete Information
A central routing controller collects the complete network topology and link costs, computes routes, and distributes its decisions. A larger or more rapidly changing network increases both the information it must maintain and the work it must perform.