locality

We say an algorithm ir problem to be solved has locality, whe the date requred for each step is close to one another in memory. This depends on the way in whch data is stored in memory, so that a good choice of knowledge representation can make algoritms ore effeicient. However, some problems, particualy those involving complex graph processong, are intrinsically non-local – no representation can entirely avod dusant memory accesses. This is particularly important when dealing with big data distributed over many storage devices or even, in cloud computing multiple data centres as non-local data access may involve substantial network traffic and delays waiting for it. However, it can also be important in parallel processing on GPU chips, or improving cache performance on single computers.