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ComputerAided_Design_Engineering_amp_Manufactur.pdf

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FIGURE 9.15 (a) Nodes represented by expressions, (b) nodes represented by pointers.<br />

In this ex<strong>amp</strong>le, variable z is fixed in order to have as many equations as unknowns.<br />

Two tree structures are built to have fixed value at the end of branches as shown in Figure 9.15. The equivalent<br />

tree structure is exhibited in Figure 9.15(a) and includes all parameters and variables. Notice that constants<br />

occupy the terminal nodes. In Figure 9.15(b), all nodes are numbered in pointerindices. In determining the<br />

execution sequence, the problem is breaking down into smaller subproblems. Subproblems are solved in a<br />

sequence such that any subproblems of the same type will not be solved more than once. An ‘‘and/or’’ graph<br />

algorithm is applied here that makes a list of all pointers to unknowns for each node in a given level. These<br />

lists are then sorted according to tree levels and merged roots a and b, because the adjacency matrix has all<br />

the information regarding both roots; it is possible to evaluate an individual root as well as all roots present<br />

in the system. To determine the execution sequence for this ex<strong>amp</strong>le, we have for nodes<br />

© 2001 by CRC Press LLC<br />

a:<br />

Level unknown pointers<br />

4 none ...<br />

3 y 1<br />

2 x, y 3, 1<br />

1 a 4<br />

b:<br />

z �<br />

Constant<br />

level unknown pointers<br />

4 none ...<br />

3 y 1<br />

2 x 3<br />

1 b 2

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