Parallel Computer Architecture

4.3 Evaluating an Architectural Idea or Trade-off 231

erally decrease with problem size, the benefit of an improved communication archi-

tecture can often be seen in the ability to run smaller problems well. Keeping

parallel efficiency fixed as the number of processors increases, in a sense, introduces

a new scaling model that we might call

efficiency-constrained

scaling.

Of course, this

metric must be used with care since capacity effects may dominate communication

differences and small problems may fail to stress important aspects of the system.

Parallel efficiency is useful but is not a general performance metric.

Percentage Improvement i ...