In this section we present some basic performance measurements to show that
NetStream is usually as fast as a raw MPI program, with a slight
overhead when sending packed data. The tests have been performed in a 100 Mbps
Fast-Ethernet cluster. We analyze the exchanges between two stations in this
cluster (Pentium III, 700 Mhz, 128 Mb RAM).
In Figure 1 we show the time in milliseconds of sending different
amount of data of the basic
char", \verb"int" and \verb"double values.
It can be observed that there is no overhead of
NetStream over MPI for
any amount of data.
In Figure 2 we show the trends for packets of different lengths of
the basic data types
int" and \verb"double as they are very usual in
numerical applications. A small overhead is then detected, especially for very
long packets. The user must decide whether these small delays is worth-wile in
the application at hands. In a WAN environment, and e.g. for optimization
tasks, the packets are usually in the region of less than 2 Kb, and the
overhead can be ignored.