The C90 computer itself is already a parallel computer (with shared memory). In order to measure the effects of clustering several C90 systems rather than measuring the overall parallel efficiency (counting all computing nodes involved), we define the following expression as cluster speed-up
and as cluster efficiency
Here P denotes the number of supercomputers (C90 systems) used in the cluster
and 
the computing time of
the parallel code on a cluster consisting of P systems.
For the parallel IFS code, we consider the 2D partitioning
consisting of 
processes.
We assume that the parallel code is partitioned to the cluster
situation in an appropriate way. represents always the
shortest runtime among all partitionings and mappings implemented with the IFS
version RAPS 2.0.