LogP Model. Motivation BSP Model Limited to BW of Network (g) and Load of PE Requires large load per super steps. Need Better Models for Portable Algorithms Converging Hardware Independent from Network Topology Programming Models Assumption
Limited to BW of Network (g) and Load of PE
Requires large load per super steps.
L,o,g : independent from P or node distances
Message length: short message
L,o,g are per word or per message of fixed length
k word message: k short messages (k*o overhead)
L independent from message length
sum with T-g as the root.
FFT on the Butterfly network
remaining can be also local
Communication time: g* (n/P**2) (P-1) + L
each PE has n/P data, each of 1/P goes to each other PE
Total time is (1+g/logn) optimal
topology independent usually works for n=1024 nodes.
The difference between average distance and max distance are not such different