On the BLI-model of program behaviour

Abstract

The BLI-model of program behaviour is sometimes referred to as an exact measure of the locality structure of the programs. However, only limited experimental data is available of the applicability of the BLI-model. In this paper the characteristics of the BLI-model are studied with relatively large empirical data. References to code segments, data segments and references to paged data segments are used in the experiments. The good coverage percentages reported in earlier studies with data segments, are present in our data also. However, the code referencing behaviour turns out to be totally different. Typically only some 50% of the execution time is covered with BLI's of acceptable length. This is shown to be a consequence of occasional references to segments not belonging to the phase or joining the phase during the phase. The behaviour of paged data segments is typically nearer to the behaviour of the code segments than that of the data segments. The BLI-model is also compared with the VMIN-algorithm. A relatively close correspondence between reasonably long BLI's and the VMIN-sets is observed. In general, the results reported in this paper indicate, that the BLI-model can be used with data segments only, or when information concerning short stable phases of the execution is sufficient.