Biomedical Parallel Image Processing on Propal 2

Abstract

PROPAL 2 is a mini parallel associative computer with an SIMD architecture. Each Processing Element (PE) works in a serial bit mode, with words of variable length from 1 to 256 bits. The most sophisticated feature of this computer is a special bus called “ascenseur” which allows an easy loading of data from the host computer and performs shifting of information from one PE to others. The assembly language is an overset of the MITRA SEMS assembler. Thus programming is done in FORTRAN through assembly language subroutines in order to improve the already existing software. The ability to work on variable length words gives PROPAL 2 a great efficiency in picture processing. On large picture processing problems (scaling — filtering — convolution — feature extraction ...), the computation time T_p of PROPAL 2 is given by:

$${{T}_{p}}\underline{\tilde{\ }}1,4{{T}_{M}}/NPE$$

where T_M is the computation time of a standard mini-computer (with floating point arithmetic unit) and NPE the number of elementary processors.

Compared to a SEMS MITRA 15–35, PROPAL 2 with “128 PE” being a standard configuration, the average gain to be expected is close to 90, but it depends on the problem. Real interactivity, which is a key problem in picture processing is then achieved.

A practical application will be shown.