GB1284421A - Data processing apparatus - Google Patents

Abstract

1284421 Determining optimum path J L SAUVAN 18 Sept 1969 [19 Sept 1968] 45976/69 Heading G4A Data processing apparatus is arranged to perform a method for the search for a set of optimum component trajectories in a set of networks, which includes starting a retrograde search from each of the target points of the networks and, when all the starting points have been reached by the search, identifying and storing for each network, as belonging to the optimum component trajectory sought, the last node reached by the retrograde search before the starting point, this last node then being used as a fresh starting point for a further retrograde search from the same target point. The set of optimum component trajectories, one per network, constitute an optimum trajectory for the set of networks, i.e. minimum length consistent with constraints. Assuming a network can be defined on a 12 x 12 grid with the links between nodes being no more than 2 units in either direction along each of the two co-ordinate directions in the grid, the apparatus of Fig. 3 permits the starting and target points for this network to be stored together with links traversed during the searches. Each small box is an element with one or more bi-stables. A node is entered using one of the elements CLY in combination with one of the elements CLX to define the position on the grid, the combination setting a bi-stable in the appropriate element of CAS XY. Two successive nodes entered set an element of CIY selected by the Y position of the first and the difference in the Y positions of the two, and set an element of CIX similarly for the X co-ordinate. An element of CAA XY is set, selected by the combination of the X and Y differences. During a search, bi-stables in elements are set representing the nodes and links reached in the search under control of bi-stables already set, but subject to constraints imposed by similar bi-stables in similar circuits relating to other networks of the set. If a retrograde search ends with a plurality of trajectories established in a given network, one is selected using priority orders in the co-ordinates (i.e. not values) and in the co-ordinate-value differences along links. Fig. 22 (not shown) shows the priority circuit for the latter, which is typical. Each of the five inputs, the highest priority one of which is to be selected, has a respective AND gate followed by a respective OR gate, both connected in that order in a loop common to all these gates. A counter-decoder partially enables all the AND gates except one (corresponding to the highest priority). The highest priority input present proceeds to a respective output through an output gate enabled through an inverter by the down output level of the corresponding AND in the loop, and enters the loop through the corresponding OR to produce up levels from the loop ANDs of lower priority (to disable the corresponding output gates). By driving the counter, the priority order is cyclically permuted. Co-ordinates can be removed from participation, and constraints can be suppressed. Shift registers can be used to weight nodes and links (producing multiple delays thereat during search). As each node of each optimum component trajectory is found, the node identity is supplied to an external system, e.g. controlled in real-time. Further information from this system may alter the stored information during determination of the optimum component trajectories, so that the trajectories being sought are continually changing. Several systems can be controlled concurrently, with some duplication of bi-stables &c. Each element of CAS XY may have some sort of information processing arrangement allotted to it and activated when the element is energized and the result may intervene in the above operations. The outputs from CIY and CIX in Fig. 3 towards CAA XY may instead go to the CLX and CLY of another system as in Fig. 3, permitting constraints relating to successions of links traversed to be memorized. Reference is made to Specification 1,284,422.