locality

1. In sequential architectures programs tend to access data

that has been accessed recently (temporal locality) or that is

at an address near recently referenced data (spatial

locality). This is the basis for the speed-up obtained with a

cache memory.

2. In a multi-processor architecture with distributed memory

it takes longer to access the memory attached to a different

processor. This overhead increases with the number of

communicating processors. Thus to efficiently employ many

processors on a problem we must increase the proportion of

references which are to local memory.

(1995-02-28)