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80 CHAPTER 5. ND-SYSTEMS APPROACH IN POLYNOMIAL OPTIMIZATION<br />

(a)<br />

(b)<br />

Figure 5.19: Region of points that occur in (a) 2-dimensional paths and (b) 3-<br />

dimensional paths<br />

Because the paths in the nD-systems approach for polynomial optimization are<br />

short and have much overlap, the use of parallel computations is not advisable. The<br />

overhead of communication is <strong>to</strong>o high in this case, especially for high-dimensional<br />

problems. In this particular case of polynomial optimization the difference between<br />

the performance of the linear method and the least-increments method will not be<br />

that high because of the shortness of the occurring paths.<br />

As said before in the beginning of this section, in a more general case, parallelization<br />

can be an improvement of the efficiency of the nD-system. One can imagine<br />

that in a certain application one wants <strong>to</strong> compute the action of a matrix A r , where<br />

r is a polynomial of high degree containing a lot of terms, without construction this<br />

matrix explicitly. The nD-system in such a case contains long separate paths with<br />

little overlap and therefore every path can be considered by a single processor. Parallelization<br />

even becomes more suitable when the number of variables increases in such<br />

a situation, but this still requires further research.

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