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Portability vs. Optimisation and economical aspects

Although portable software-interfaces are available, this does not mean, that the generated code has high efficiency on any particular machine. Machines are too different. Some offer very fast synchronisation-mechanisms and low latency (e.g. Cray-T3D), others have hardware for good latency-hiding and asynchronity (e.g. intel Paragon) and others again have only a very fast processor (e.g. IBM SP/2). This means, that, starting with a parallelized code, there is still a lot of effort and time to be spent, until results are satisfactory. The following figure shows the history of LS-DYNA3D on the intel Paragon from the parallelized version to a really usable and cost-effictive solution. The scale on the right side shows the calculated cost relative to one processor of a Cray C-90. This means that the initial parallel code was neither cost-effective nor fast.
The final result however (after half a year of further optimisation) saves about 60-70 % of the cost at about the same turnaround-time. The testcase is a crash example from Audi.

Figure 1: Are MPPs an economic solution?
Tue Nov 14 16:00:38 PST 1995