An iterative parallel region growing (IPRG) algorithm, developed and implemented on the massively parallel processor (MPP) at NASA Goddard, is described. The experience of porting the IPRG algorithm from the MPP to the MasPar MP-1 is related. Porting was very easy and straightforward, especially when the Dorband virtualization software was used. The porting discussed, consisting of 1879 lines of MPL code, was accomplished in just two weeks by the author. The major difference between the two implementations is that the looping over virtual parallel arrays had to be done explicitly and had to be the outermost loop (for efficiency) in the MPP Pascal implementation, whereas the same looping was done implicitly in the MPL implementation and could be done in the innermost loop. In a performance test on a 256*256 pixel section of a seven-band Landsat thematic mapper image data set, the smaller MasPar MP-1 computer had roughly the same or better performance as the MPP. In the initial iterations, when the regions were still very small, the MPP was about 25% faster than the MasPar MP-1. By iteration 14, the MasPar MP-1 was 33% faster than the MPP, and for ensuing iterations indications are that the MasPar MP-1 speedup versus the MPP will be even larger.
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