If it is some such tops, the preference is given to top with the maximum number of multiple edges. From a set of the tops adjacent to tops of the formed piece the column G1(X1,U, choose that which provides the minimum increment of communications of a piece with even unallotted tops. This top of xi X \X1 is included in G1(X1,U if there is no violation of restriction on number of external relations of a piece, i.e.
where p and h (p) – serial number and a position of fixing of the motionless rp element. If, carry out the shift of ri and rj leading to reduction of criterion function on then run for search and shift of the following couple of elements, etc. Process comes to an end with receiving such option of placement for which further improvement due to pair shifts of elements is impossible.
The main lack of consecutive algorithm is inability to find a global minimum of quantity of external relations (possible situations are not analyzed). The greatest efficiency of a method of consecutive splitting the count takes place, when number of tops column G much more tops in any part of splitting.
After transformation of a piece of G10(X10,U1 process is repeated for formation of the pieces of the initial count second, third, etc. with only that difference that the tops which did not enter the previous pieces are subject to consideration.
The greatest distribution in algorithms of placement was gained by the first criterion that is explained by the following reasons: reduction of lengths of connections improves electric characteristics of the device, simplifies trace of printed-circuit boards; besides, it is rather simple in realization.
The element wk, q of a matrix of W characterizes change of number of connecting edges between Gi and Gj at shift of tops and. Using W matrix, it is possible to find substitution which will increase number of elements in submatrixes of R1 and R1’. Such process repeats until in a submatrix of R1 the maximum number of units does not concentrate.
Simultaneous optimization of all connections at trace due to search of all options it is impossible now. Therefore generally locally optimum methods of trace when the route is optimum only on this step in the presence of earlier carried out connections are developed.
The orthogonal algorithms possessing big speed, than algorithms of the first group. Realization on the COMPUTER demands them 75-100 times less calculations in comparison with wave algorithms. Such algorithms apply at design of printed-circuit boards with the through metallized openings. Shortcomings of this group of algorithms are connected with receiving a large number of transitions from a layer to a layer, lack of a 100% guarantee of carrying out routes, a large number in parallel of the going conductors;