JP5502802B2 - Route determining apparatus and route determining method - Google Patents

Description

  The present invention relates to a route determination device and a route determination method for determining a shortest route between two nodes in a communication network composed of a plurality of nodes.

  In a communication network composed of a plurality of nodes connected to adjacent nodes via links, the node is a node other than the start point node among the plurality of nodes from the start point node that is one of the plurality of nodes. There may be a plurality of communication paths to the end node. Therefore, it is necessary to determine the shortest route that is the most efficient communication route among the plurality of communication routes.

  Therefore, by setting a weight value called a cost value for the link and calculating the cost value of each of the plurality of communication paths from the start node to the end node, the communication path with the minimum cost value is determined as the shortest path. It is common.

  For example, Non-Patent Document 1 discloses a Dijkstra method that is one of the algorithms for determining the shortest path by the calculation as described above.

  FIG. 8 is a flowchart for explaining the operation of determining the shortest path using the Dijkstra method.

  First, it is confirmed whether or not there is a node that is not selected as a starting point node among a plurality of nodes constituting the communication network (step S101).

  As a result of the confirmation in step S101, if there is no node that is not selected as the start point node, the process ends.

  On the other hand, if there is a node not selected as the start point node as a result of the confirmation in step S101, one of the nodes not selected as the start point node is selected as the start point node (step S102). Note that the node selected as the start point node is recognized as the end point node of the determined shortest path.

  Next, when there is a node adjacent to the end point node of the determined shortest path and the shortest path from the start point node is not determined, the communication path from the start point node to the node is set as the shortest path candidate, A cost value is calculated (step S103).

  Next, it is confirmed whether or not the shortest path candidate exists (step S104).

  If the shortest path candidate exists as a result of the confirmation in step S104, the shortest path candidate having the minimum cost value is determined as the shortest path (step S105), and the operation proceeds to step S103.

  On the other hand, as a result of the confirmation in step S104, if there is no shortest path candidate, the operation proceeds to step S101.

  Thereafter, the operations in steps S101 to S105 are repeated, and the shortest path is determined when each of the plurality of nodes constituting the communication network is set as the start node.

  9 to 11 are diagrams for explaining a specific example of the operation for determining the shortest path according to the flowchart shown in FIG. 8, (a) is a diagram showing an example of a communication network, and (b) is a diagram. It is a figure which shows an example of the shortest path | route candidate. Here, a specific example of the operation in which the shortest path is determined will be described with reference to FIGS.

  Note that the communication networks shown in FIGS. 9A, 10A, and 11A are the same.

  Further, in FIG. 9A, FIG. 10A and FIG. 11A, the nodes are indicated by circles, and the alphabets described in the circles indicate a plurality of nodes constituting the communication network. Each has been identified. Hereinafter, for example, a node described as A in a circle is referred to as a node A. The communication path is expressed using <>. For example, in the case of a communication path from node A to node B, it is expressed as <A → B>.

  In FIGS. 9A, 10A, and 11A, a solid line or a broken line between circles indicating nodes indicates a link, and a number in the vicinity of the link indicates the link. The set cost value is shown.

  First, in accordance with the operation of step S101 described above, it is confirmed whether there is a node that is not selected as the start point node among the nodes A to I configuring the communication network. Here, it is assumed that none of the nodes A to I is selected as the start point node.

  Therefore, one of the nodes A to I is selected as the start point node in accordance with the operation of step S102 described above. Here, it is assumed that node A is selected as the start point node. Thereby, the node A is recognized as the end point node of the determined shortest path.

  Next, according to the operation of step S103 described above, a communication path to a node that is adjacent to node A and for which the shortest path from node A has not yet been determined is the shortest path candidate, and a cost value is calculated. Here, nodes that are adjacent to node A and whose shortest path from node A has not been determined are node B, node C, and node D.

  Therefore, three of <A → B>, <A → C>, and <A → D> are shortest path candidates. The communication path that has been the shortest path candidate so far is shown in FIG. 9B, and is shown by a solid line in FIG. 9A.

  Next, whether the shortest path candidate exists is confirmed according to the operation of step S104 described above. Here, there are three shortest path candidates as shown in FIG. That is, there is a shortest path candidate. Therefore, in accordance with the operation of step S105 described above, among the three shortest path candidates, <A → D> having the minimum cost value is determined as the shortest path.

  Next, the process proceeds to the operation of step S103 described above, and a communication path to a node that is adjacent to the node D and for which the shortest path from the node A has not yet been determined is the shortest path candidate, and a cost value is calculated. Here, the nodes that are adjacent to the node D and whose shortest path from the node A has not been determined are the node E, the node F, and the node G.

  Therefore, in addition to <A → B> and <A → C> that are already shortest path candidates, <A → D → E>, <A → D → F>, and <A → Three of D → G> are shortest path candidates. The communication path that has been the shortest path candidate so far is shown in FIG. 10B, and is shown by a solid line in FIG. <A → D> has already been determined as the shortest route, and is excluded from the shortest route candidates.

  Next, whether the shortest path candidate exists is confirmed according to the operation of step S104 described above. Here, there are five shortest path candidates as shown in FIG. That is, there is a shortest path candidate. Therefore, according to the operation of step S105 described above, among the five shortest path candidates, <A → D → F> having the minimum cost value is determined as the shortest path.

  Next, the process proceeds to the above-described operation of step S103, and a communication path to a node that is adjacent to the node F and for which the shortest path from the node A has not yet been determined is the shortest path candidate, and a cost value is calculated. Here, the nodes adjacent to the node F and whose shortest path from the node A has not been determined are the node H and the node I.

  Therefore, in addition to the four shortest path candidates <A → B>, <A → C>, <A → D → E>, and <A → D → G>, <A → B> Two of D → F → H> and <A → D → F → I> are shortest path candidates. The communication path that has become the shortest path candidate so far is shown in FIG. 11B, and is shown by a solid line in FIG. Note that <A → D → F> has already been determined as the shortest path, and is therefore excluded from the shortest path candidates.

  Next, whether the shortest path candidate exists is confirmed according to the operation of step S104 described above. Here, there are six shortest path candidates as shown in FIG. That is, there is a shortest path candidate. Therefore, in accordance with the operation of step S105 described above, among the six shortest path candidates, <A → C> having the minimum cost value is determined as the shortest path.

  Such an operation is repeated until the shortest path from the node A to each of the nodes B to I is determined. Then, when the shortest path from the node A to each of the nodes B to I is determined, the shortest path when each of the nodes B to I is set as the start node is determined. Then, when the shortest path is determined when all the nodes A to I are set as the start point nodes, the calculation for determining the shortest path ends.

Dijkstra, E. W. (1959). "A note on two problems in connexion with graphs" .Numerische Mathematik 1: 269-271

  An algorithm such as the Dijkstra method described above is the shortest path candidate for all communication paths from the start point node to the end point node of the determined shortest path and the shortest path from the start point node to the undecided node. Add as Therefore, when the node is adjacent to many other nodes via links, the number of shortest path candidates increases. In this case, there is a problem that the amount of calculation for determining the shortest path candidate having the minimum cost value increases, and the time until the shortest path is determined becomes long.

  The present invention relates to a route determination method and a route determination device capable of avoiding an increase in the time until determining the shortest route when a node is adjacent to many other nodes via a link. The purpose is to provide.

In order to achieve the above object, the route determination device according to the present invention includes a node other than the node among the plurality of nodes connected to the adjacent nodes via the link in which the cost value is set. A route determination device that determines the shortest route to an end point node,
A selection unit that selects each of the plurality of nodes one by one as a starting point node;
The start point node selected by the selection unit is recognized as the end point node of the determined shortest path, and then from the start point node, adjacent to the end point node of the determined shortest path, and from the start point node A communication route to an undetermined node whose shortest route is an undetermined node is determined as a shortest route candidate that is a candidate for the shortest route, and among the shortest route candidates, a shortest route candidate having a minimum cost value is determined as the shortest route And repeatedly recognizing the end node of the determined shortest path as the end node of the determined shortest path instead of the node recognized as the end node of the determined shortest path. And
The determination unit determines a communication path from the start point node to an undecided node having a minimum cost value set in a link between the undecided node and an end point node of the determined shortest path. Let it be the shortest path candidate.

In addition, in order to achieve the above object, the route determination method of the present invention uses a node other than the node among the plurality of nodes connected to each other via a link in which a cost value is set with an adjacent node. A route determination method in a route determination device for determining a shortest route to an end node that is a node of
A process of selecting each of the plurality of nodes as a starting point node;
Processing for recognizing the selected start point node as the end point node of the determined shortest path;
The communication path from the start node to the undecided node that is adjacent to the end node of the determined shortest path and whose shortest path from the start node is an undecided node is the shortest candidate for the shortest path. The shortest path candidate having the lowest cost value is determined as the shortest path among the shortest path candidates, and the end node of the determined shortest path is recognized as the end node of the determined shortest path. Instead of the existing node, a determination process that repeats newly recognizing as an end node of the determined shortest path, and
In the determination process, a communication path from the start point node to an undecided node having a minimum cost value set to a link between the undecided node and an end point node of the determined shortest path is Let it be the shortest path candidate.

  Since the present invention is configured as described above, all of the communication paths from the start point node to the end point node of the determined shortest path and from the start point node to the undecided node Is not added to the shortest path candidate.

  Therefore, the number of shortest path candidates is suppressed, and the amount of calculation when determining the shortest path with the minimum cost value can be reduced.

  Therefore, when a node is adjacent to many other nodes via a link, it is possible to avoid an increase in the time until the shortest path is determined.

It is a figure for demonstrating the property of the algorithm of a Dijkstra method. It is a block diagram which shows the structure of one Embodiment of the route determination apparatus of this invention. 3 is a flowchart for explaining an operation in which the route determination device shown in FIG. 2 determines the shortest route. 3 is a flowchart for explaining details of an operation in which the route determination device shown in FIG. 2 determines the shortest route. FIG. 5 is a diagram for explaining a specific example of an operation in which the route determination device determines the shortest route according to the flowcharts shown in FIGS. 3 and 4. FIG. 5 is a diagram for explaining a specific example of an operation in which the route determination device determines the shortest route according to the flowcharts shown in FIGS. 3 and 4. FIG. 5 is a diagram for explaining a specific example of an operation in which the route determination device determines the shortest route according to the flowcharts shown in FIGS. 3 and 4. It is a flowchart for demonstrating the operation | movement which determines the shortest path | route using the Dijkstra method. It is a figure for demonstrating the specific example of the operation | movement which determines the shortest path | route according to the flowchart shown in FIG. 8, (a) is a figure which shows an example of a communication network, (b) shows an example of the shortest path candidate. FIG. It is a figure for demonstrating the specific example of the operation | movement which determines the shortest path | route according to the flowchart shown in FIG. 8, (a) is a figure which shows an example of a communication network, (b) shows an example of the shortest path candidate. FIG. It is a figure for demonstrating the specific example of the operation | movement which determines the shortest path | route according to the flowchart shown in FIG. 8, (a) is a figure which shows an example of a communication network, (b) shows an example of the shortest path candidate. FIG.

  In the following, embodiments of the present invention will be described with reference to the drawings, but before that, the nature of the algorithm of the Dijkstra method described above will be described.

  FIG. 1 is a diagram for explaining the nature of the Dijkstra algorithm. Here, the description will be made based on a plurality of nodes and cost values constituting the communication network shown in FIG. 9A, FIG. 10A, and FIG.

  1 (a), FIG. 1 (b), FIG. 1 (d), FIG. 1 (e), and FIG. 1 (f) are the end points of the shortest path determined in the operation described with reference to FIGS. Communication paths from a node to an adjacent node through a link with the end node are arranged in ascending order of cost value.

  Specifically, FIG. 1 (a) and FIG. 1 (d) describe communication paths between node A and nodes adjacent to node A through links in order of increasing cost values. It is. FIG. 1B and FIG. 1E show communication paths between the node D and a node adjacent to the node D via a link in order of increasing cost values. FIG. 1F shows communication paths between the node F and nodes adjacent to the node F via links in order of increasing cost values.

  First, when <A → D> is determined as the shortest path, the communication paths shaded in FIGS. 1A and 1B are the communication paths to the nodes on the determined shortest path. Therefore, it is excluded from the target when considering the shortest path candidate.

  FIG. 1C shows the shortest path candidates after <A → D> is determined as the shortest path in order of increasing cost value.

  Among the shortest path candidates shown in FIG. 1C, the order of the shortest path candidates from the node A to the node adjacent to the node A is the same as the order shown in FIG. That is, in FIG. 1A and FIG. 1C, <A → C> is higher than <A → B>.

  Further, among the shortest path candidates shown in FIG. 1C, the order of the shortest path candidates from the node A through the node D to the node adjacent to the node D is from the node D to the node adjacent to the node D. When attention is paid to the communication path, the order is the same as that shown in FIG. That is, <D → F> is higher than <D → G> and <D → E> in FIG. 1B, and <A → D → F> is <A → D → G in FIG. 1C. > And <A → D → E>. In FIG. 1B, <D → G> is higher than <D → E>, and in FIG. 1C, <A → D → G> is higher than <A → D → E>. ing.

  Next, when <A → D → F> is determined as the shortest path, the communication paths shaded in FIG. 1 (d), FIG. 1 (e), and FIG. 1 (f) are the shortest determined paths. Since it becomes a communication route to a node on the route, it is excluded from the target when considering the shortest route candidate.

  FIG. 1G shows the shortest path candidates after <A → D → F> determined as the shortest path arranged in order of increasing cost value.

  Among the shortest path candidates shown in FIG. 1G, the order of the shortest path candidates from the node A to the node adjacent to the node A is the same as the order shown in FIG. In addition, among the shortest path candidates shown in FIG. 1 (g), the order of the shortest path candidates from the node A to the node adjacent to the node D via the node D is from the node D to the node adjacent to the node D. When attention is paid to the communication path, the order is the same as that shown in FIG.

  Further, among the shortest path candidates shown in FIG. 1G, the order of the shortest path candidates from the node A to the nodes adjacent to the node F via the nodes D and F is adjacent to the node F to the node F. When attention is paid to the communication path to the node to be operated, the order is the same as that shown in FIG. That is, <F → I> is higher than <F → H> in FIG. 1 (f), and <A → D → F → I> is higher than <A → D → F → H> in FIG. 1 (g). Is also ranked high.

  In this way, even when the shortest route is newly determined and the shortest route candidate is added, the shortest route candidate is, for each end node of the determined shortest route, the end node and a node adjacent to the end node. The cost values set for the links connecting are arranged in ascending order. In other words, the shortest path is determined for each end node of the determined shortest path in order of increasing cost value set for the link connecting the end node and the node adjacent to the end node. become.

  This is because the cost value from the start node to the end node of the determined shortest path is the same, the end node is adjacent to the end node, and the shortest path from the start node is undecided. This is because the difference between the cost values set for the links connecting the two becomes the difference between the cost values of the shortest path candidates.

  Therefore, when determining the shortest path, the node between the start node and the end node of the determined shortest path that is adjacent to the end node and the shortest path from the start node is not determined. Only the communication path to the node having the minimum cost value set for the link may be added as the shortest path candidate. In this embodiment, the shortest path candidate is added in this way.

  FIG. 2 is a block diagram showing the configuration of an embodiment of the route determination device of the present invention.

  As illustrated in FIG. 2, the route determination device according to the present exemplary embodiment includes a storage unit 11, a selection unit 12, and a determination unit 13.

  The storage unit 11 stores network configuration information indicating a communication network. The network configuration information includes information indicating a plurality of nodes constituting the communication network and information indicating a cost value set for the link.

  The selection unit 12 receives the selection instruction output from the determination unit 13. The selection instruction is an instruction for selecting one of a plurality of nodes constituting the communication network indicated by the network configuration information stored in the storage unit 11 as a start node. Hereinafter, the plurality of nodes constituting the communication network indicated by the network configuration information stored in the storage unit 11 are simply referred to as a plurality of nodes. Upon receiving the selection instruction output from the determination unit 13, the selection unit 12 confirms whether there is a node that is not selected as the start point node among the plurality of nodes. Note that the selection unit 12 performs this confirmation every time the selection instruction output from the determination unit 13 is received. As a result of the confirmation, when there is a node that is not selected as the start point node among the plurality of nodes, the selection unit 12 selects one of the nodes that are not selected as the start point node as the start point node. Then, the selection unit 12 outputs start point node information indicating the selected start point node to the determination unit 13.

  The determination unit 13 generates cost order information for each of the plurality of nodes. The cost order information is information in which communication paths between a node and a node adjacent to the node via a link are arranged in ascending order of cost values. Next, the determination unit 13 outputs a selection instruction to the selection unit 12. Thereafter, the determination unit 13 receives the start point node information output from the selection unit 12. Then, the determination unit 13 determines the shortest path from the start point node indicated by the received start point node information to all the nodes other than the start point node among the plurality of nodes. Then, the determination unit 13 outputs a selection instruction to the selection unit 12. The details of the operation of the determination unit 13 determining the shortest path will be described later.

  Below, the operation | movement which determines the shortest path | route in the route determination apparatus 10 comprised as mentioned above is demonstrated.

  FIG. 3 is a flowchart for explaining an operation in which the route determination device 10 shown in FIG. 2 determines the shortest route.

  First, the determination unit 13 generates cost order information for each of a plurality of nodes (step S1).

  Then, the determination unit 13 outputs a selection instruction to the selection unit 12.

  The selection unit 12 that has received the selection instruction output from the determination unit 13 checks whether there is a node that is not selected as the start point node among the plurality of nodes (step S2).

  As a result of the confirmation in step S2, if there is no node that is not selected as the start point node among the plurality of nodes, the process is terminated.

  On the other hand, as a result of the confirmation in step S2, if there is a node that is not selected as the start point node among the plurality of nodes, the selection unit 12 selects one of the nodes that are not selected as the start point node as the start point node. (Step S3).

  Then, the selection unit 12 outputs start point node information indicating the selected start point node to the determination unit 13.

  The determination unit 13 that has received the start point node information output from the selection unit 12 determines the shortest path from the start point node indicated by the received start point node information to all the nodes other than the start point node among the plurality of nodes ( Step S4).

  Next, the determination unit 13 outputs a selection instruction to the selection unit 12. And it changes to operation | movement of step S2.

  Thereafter, the operations in steps S2 to S4 are repeated, and the shortest path when each of the plurality of nodes is set as the start point node is determined.

  Next, details of the operation for determining the shortest path in step S4 will be described.

  FIG. 4 is a flowchart for explaining details of an operation in which the route determination device 10 shown in FIG. 2 determines the shortest route. Here, a node adjacent to the end point node of the determined shortest path on the determined shortest path on the start point node side is defined as a parent node of the end point node.

  First, the determination unit 13 recognizes the start point node indicated by the received start point node information as the end point node of the determined shortest path (step S41).

  Next, the determination unit 13 confirms whether or not there is an undetermined node that is adjacent to the end point node of the determined shortest path and whose shortest path from the start point node is undetermined (step S42). .

  As a result of the confirmation in step S42, when there is a node that is adjacent to the end point node of the determined shortest path and whose shortest path from the start point node has not been determined, the determination unit 13 includes the cost order information of the end point node. Of the included communication routes, the communication route that is determined by adding the determined shortest route to the highest communication route excluding the communication route to the node on the determined shortest route is used as the shortest route candidate, and the cost value is calculated. (Step S43).

  Next, the determination unit 13 confirms whether there is a node that is adjacent to the parent node of the end point node of the determined shortest path and whose shortest path from the start point node has not been determined (step S44).

  As a result of the confirmation in step S44, when there is a node that is adjacent to the parent node of the end node of the determined shortest path and whose shortest path from the start node is not determined, the determination unit 13 determines the cost of the parent node. Of the communication paths included in the order information, the communication path that is the highest level excluding the communication path to the node on the determined shortest path, and the communication path from the start node to the parent node among the determined shortest paths The cost value is calculated with the communication route with the added as the shortest route candidate (step S45).

  Next, the determination part 13 confirms whether the shortest path candidate exists (step S46).

  If the shortest path candidate exists as a result of the confirmation in step S46, the shortest path candidate having the minimum cost value is determined as the shortest path (step S47).

  Next, instead of the node recognized as the end node of the determined shortest path, the determination unit 13 newly sets the end node of the shortest path determined in step S47 as the end node of the determined shortest path. Recognize (step S48). And it changes to operation | movement of step S42.

  As a result of the confirmation in step S42, if there is no node adjacent to the end point node of the determined shortest path and the shortest path from the start point node is not determined, the process proceeds to step S44.

  Further, as a result of the confirmation in step S44, if there is no node adjacent to the parent node of the end node of the determined shortest path and the shortest path from the start point node is not determined, the process proceeds to step S46.

  If no shortest path candidate exists as a result of the confirmation in step S46, the process ends. This is a case where the shortest path from the start point node to all the nodes other than the start point node among the plurality of nodes has been determined. In this case, the process proceeds to the operation of step S2 described with reference to FIG.

  Next, a specific example of the operation in which the route determination device 10 determines the shortest route will be described according to the flowcharts shown in FIGS. 3 and 4.

  5 to 7 are diagrams for explaining specific examples of operations in which the route determination device 10 determines the shortest route according to the flowcharts shown in FIGS. 3 and 4. Here, a specific example of the operation in which the route determination device 10 determines the shortest route will be described with reference to FIGS.

  5A, 6 </ b> A, and 7 </ b> A illustrate the communication network indicated by the network configuration information stored in the storage unit 11. This communication network has the same configuration as the communication network shown in FIGS. 9A, 10A, and 11A.

  FIGS. 5B, 6B, and 7B show the cost order information of the node A, and FIGS. 6C and 7C show the cost order information of the node D. FIG. 7D shows the cost order information of the node F.

  First, according to the operation of step S1 described above, the determination unit 13 generates cost order information for each of the nodes A to I.

  Next, according to the operation in step S2 described above, the selection unit 12 checks whether there is a node that has not been selected as the start point node among the nodes A to I. Here, it is assumed that none of the nodes A to I is selected as the start point node.

  Accordingly, the selection unit 12 selects one of the nodes A to I as the start point node in accordance with the operation of step S3 described above. Here, it is assumed that the selection unit 12 selects the node A as the start point node.

  Next, according to the operation in step S41 described above, the determination unit 13 recognizes the node A as the end point node of the determined shortest path.

  Next, according to the operation of step S42 described above, the determination unit 13 confirms whether there is a node that is adjacent to the node A and for which the shortest path from the node A has not been determined. Here, nodes that are adjacent to node A and whose shortest path from node A has not been determined are node B, node C, and node D. That is, there is a node that is adjacent to node A and whose shortest path from node A has not been determined.

  Therefore, according to the operation of step S43 described above, the determination unit 13 excludes communication paths to nodes on the determined shortest path from among the communication paths included in the cost order information of the end node of the determined shortest path. The cost value is calculated by setting a communication route obtained by adding the determined shortest route to the highest communication route as the shortest route candidate. Here, there is no determined shortest path. Therefore, the determination unit 13 sets <A → D> which is the highest in the cost order information shown in FIG. 5B as the shortest path candidate.

  Next, according to the operation of step S44 described above, the determination unit 13 determines whether there is a node that is adjacent to the parent node of the end point node of the determined shortest path and whose shortest path from the start point node has not yet been determined. Check. Here, the end node of the determined shortest path is the node A, but since the node A is also the start node, there is no parent node. Therefore, there is no node that is adjacent to the parent node and for which the shortest path from the start node has not been determined. Therefore, the process proceeds to the operation in step S46 described above, and the determination unit 13 confirms whether or not the shortest path candidate exists. The communication path that has become the shortest path candidate so far is shown in FIG. 5C, and is shown by a solid line in FIG. 5A.

  Here, the shortest path candidate is one shown in FIG. That is, there is a shortest path candidate. Therefore, according to the operation in step S47 described above, the determination unit 13 determines <A → D> having the minimum cost value as the shortest path.

  Next, in accordance with the operation in step S48 described above, the determination unit 13 determines the end node of the shortest path determined in step S47 instead of the node recognized as the end node of the determined shortest path. It is newly recognized as the end node of the shortest path. Here, the determination unit 13 newly recognizes the node D as the end point node of the determined shortest path instead of the node A.

  Then, the process proceeds to the operation of step S42 described above, and the determination unit 13 confirms whether there is a node adjacent to the node D and having the undetermined shortest path from the node A. Here, the nodes that are adjacent to the node D and whose shortest path from the node A has not been determined are the node E, the node F, and the node G. That is, there is a node that is adjacent to the node D and whose shortest path from the node A is not yet determined.

  Therefore, according to the operation of step S43 described above, the determination unit 13 excludes communication paths to nodes on the determined shortest path from among the communication paths included in the cost order information of the end node of the determined shortest path. The cost value is calculated by setting a communication route obtained by adding the determined shortest route to the highest communication route as the shortest route candidate. Here, the determination unit 13 is the highest in the cost order information of the node D illustrated in FIG. 6C except for <D → A> that is a communication path to the node on the determined shortest path. <A → D → F> obtained by adding <A → D> to <D → F> is added to the shortest path candidate.

  Next, according to the operation of step S44 described above, the determination unit 13 determines whether there is a node that is adjacent to the parent node of the end point node of the determined shortest path and whose shortest path from the start point node has not yet been determined. Check. Here, the end node of the determined shortest path is node D. The parent node of node D is node A. That is, the determination unit 13 confirms whether there is a node that is adjacent to the node A and whose shortest path from the node A is not yet determined. Here, the nodes adjacent to node A and whose shortest path from node A has not been determined are node B and node C. That is, there is a node that is adjacent to node A and whose shortest path from node A has not been determined.

  Therefore, in accordance with the operation of step S45 described above, the determination unit 13 communicates with the node on the determined shortest path among the communication paths included in the cost order information of the parent node of the end node of the determined shortest path. A cost value is calculated by setting a communication path obtained by adding a communication path from the start node to its parent node among the determined shortest paths to the highest communication path except for. In the cost order information of node A shown in FIG. 6B, the highest communication path is <A → C> except for <A → D> which is the communication path to the node on the determined shortest path. It is. However, since the determined shortest path is <A → D>, there is no communication path from the start node to its parent node among the determined shortest paths. Therefore, the determination unit 13 adds <A → C> as the shortest path candidate. The communication path that has become the shortest path candidate so far is shown in FIG. 6D, and is shown by a solid line in FIG. 6A.

  Next, according to the operation in step S46 described above, the determination unit 13 confirms whether there is a shortest path candidate. Here, there are two shortest path candidates shown in FIG. That is, there is a shortest path candidate. Therefore, according to the operation in step S47 described above, the determination unit 13 determines <A → D → F> having the minimum cost value as the shortest path among the two shortest path candidates.

  Next, in accordance with the operation in step S48 described above, the determination unit 13 determines the end node of the shortest path determined in step S47 instead of the node recognized as the end node of the determined shortest path. It is newly recognized as the end node of the shortest path. Here, the determination unit 13 newly recognizes the node F as the end point node of the determined shortest path instead of the node D.

  Then, the process proceeds to the operation in step S42 described above, and the determination unit 13 confirms whether there is a node adjacent to the node F and having the undetermined shortest path from the node A. Here, the nodes that are adjacent to the node F and whose shortest path from the node A has not been determined are the node H and the node I. That is, there is a node that is adjacent to the node F and whose shortest path from the node A is not yet determined.

  Therefore, according to the operation of step S43 described above, the determination unit 13 excludes communication paths to nodes on the determined shortest path from among the communication paths included in the cost order information of the end node of the determined shortest path. The cost value is calculated by setting a communication route obtained by adding the determined shortest route to the highest communication route as the shortest route candidate. Here, the determination unit 13 is the highest in the cost order information of the node F illustrated in FIG. 7D except for <F → D> which is a communication path to the node on the determined shortest path. <A → D → F → I> obtained by adding <A → D → F> to <F → I> is added to the shortest path candidate.

  Next, according to the operation of step S44 described above, the determination unit 13 determines whether there is a node that is adjacent to the parent node of the end point node of the determined shortest path and whose shortest path from the start point node has not yet been determined. Check. Here, the end point node of the determined shortest path is the node F. The parent node of node F is node D. That is, the determination unit 13 confirms whether there is a node that is adjacent to the node D and for which the shortest path from the node A has not been determined. Here, the nodes that are adjacent to the node D and whose shortest path from the node A has not been determined are the node E and the node G. That is, there is a node that is adjacent to the node D and whose shortest path from the node A is not yet determined.

  Therefore, in accordance with the operation of step S45 described above, the determination unit 13 communicates with the node on the determined shortest path among the communication paths included in the cost order information of the parent node of the end node of the determined shortest path. A cost value is calculated by setting a communication path obtained by adding a communication path from the start node to its parent node among the determined shortest paths to the highest communication path except for. Here, the determination unit 13 sets <D → F> and <D → A>, which are communication paths to the nodes on the shortest determined path, in the cost order information of the node D illustrated in FIG. <A → D → G>, in which <A → D> is added to <D → G>, which is the highest order, is added as the shortest path candidate.

  Next, according to the operation in step S46 described above, the determination unit 13 confirms whether there is a shortest path candidate.

  Here, there are three shortest path candidates as shown in FIG. That is, there is a shortest path candidate. Therefore, in accordance with the operation in step S47 described above, the determination unit 13 determines <A → C> having the minimum cost value as the shortest path among the three shortest path candidates.

  Next, in accordance with the operation in step S48 described above, the determination unit 13 determines the end node of the shortest path determined in step S47 instead of the node recognized as the end node of the determined shortest path. It is newly recognized as the end node of the shortest path. Here, instead of the node F, the determination unit 13 newly recognizes the node C as the end point node of the determined shortest path.

  Thereafter, the operations in steps S42 to S48 described above are repeated until the shortest path from the node A to each of the nodes B to I is determined. When the shortest path from the node A to each of the nodes B to I is determined, the process proceeds to the operation in step S2 described above, and one of the nodes A to I other than the node A is selected as the starting point node. .

  As described above, in this embodiment, the route determination device 10 selects the plurality of nodes one by one as the start point node, and selects the start point node selected by the selection unit 12 as the determined shortest route. It has the determination part 13 recognized as an end point node.

  Thereafter, the determination unit 13 determines the communication path from the start point node to the undecided node that is adjacent to the end point node of the determined shortest path and the shortest path from the start point node is an undecided node. The shortest route candidate that is a candidate for the route is determined, and among the shortest route candidates, the shortest route candidate with the lowest cost value is determined as the shortest route, and the end point node of the determined shortest route is set as the end point node of the determined shortest route In place of the recognized node, a new recognition as the end point node of the determined shortest path is repeated. At this time, the determination unit 13 determines the communication path from the start point node to the undecided node having the smallest cost value set for the link between the undecided nodes and the end point node of the determined shortest path. Let it be the shortest path candidate.

  As a result, the communication path from the start point node to the end point node of the determined shortest path and the shortest path from the start point node to the undecided node is not added to the shortest path candidate.

  Therefore, the number of shortest path candidates is suppressed, and the amount of calculation when determining the shortest path with the minimum cost value can be reduced.

  In the Dijkstra method described above, a communication path from a start node to a node that satisfies the following conditions (1) and (2) is set as a shortest path candidate.

(1) Adjacent to the end point node of the determined shortest path (2) The shortest path from the start point node is not yet determined In this embodiment, in addition to the above (1) and (2) from the start point node, A communication route to a node that satisfies the condition (3) below is set as the shortest route candidate.

(3) Connection with the end point note of the determined shortest path with the minimum cost value In other words, in the Dijkstra method, the number of communication paths added as shortest path candidates is determined via the end node and link of the determined shortest path. The number depends on the number of nodes to be connected. On the other hand, in the present embodiment, the number of communication paths added as shortest path candidates is only one per end node of the determined shortest path.

  In other words, in the Dijkstra method, in the process of determining the shortest path candidate with the minimum cost value as the shortest path, the communication path from the start node to the node adjacent to the end node of the determined shortest path is the cost. The values are arranged in ascending order.

  On the other hand, in this embodiment, for each of a plurality of nodes, communication paths between the node and a node adjacent to the node are arranged in advance in ascending order of cost value. In the process of determining the shortest path candidate with the minimum cost value as the shortest path, the communication path from the start node to the node with the minimum cost value among the nodes adjacent to the end node of the determined shortest path is determined. It is only added as a shortest path candidate. Therefore, it is not necessary to arrange communication paths to nodes adjacent to the same node in order of decreasing cost value each time the start node changes. Therefore, in the present embodiment, the amount of calculation can be reduced compared to the Dijkstra method.

  Therefore, when a node is adjacent to many other nodes via a link, it is possible to avoid an increase in the time until the shortest path is determined.

DESCRIPTION OF SYMBOLS 10 Route determination apparatus 11 Memory | storage part 12 Selection part 13 Determination part

Claims (4)

A route determination device that determines the shortest route from each of a plurality of nodes connected to adjacent nodes via a link with a cost value to an end node that is a node other than the node among the plurality of nodes. There,
A selection unit that selects each of the plurality of nodes one by one as a starting point node;
The start point node selected by the selection unit is recognized as the end point node of the determined shortest path, and then from the start point node, adjacent to the end point node of the determined shortest path, and from the start point node A communication route to an undetermined node whose shortest route is an undetermined node is determined as a shortest route candidate that is a candidate for the shortest route, and among the shortest route candidates, a shortest route candidate having a minimum cost value is determined as the shortest route And repeatedly recognizing the end node of the determined shortest path as the end node of the determined shortest path instead of the node recognized as the end node of the determined shortest path. And
The determination unit determines a communication path from the start point node to an undecided node having a minimum cost value set in a link between the undecided node and an end point node of the determined shortest path. A route determination device that makes a shortest route candidate. The route determination device according to claim 1,
For each of the plurality of nodes, the determination unit generates in advance cost order information, which is information in which communication paths to a node adjacent to the node are arranged in ascending order of cost values, and the determined shortest path A communication path obtained by adding the determined shortest path to the highest communication path excluding the communication path to the node on the determined shortest path in the cost order information of the end node of In the cost order information of the parent node that is the adjacent node on the start node side and the end node of the determined shortest path on the shortest path, except for the communication path to the node on the determined shortest path A communication path obtained by adding a communication path from the start node to the parent node among the determined shortest paths to the highest communication path, Routing device to. In a route determination device that determines the shortest route from each of a plurality of nodes connected to adjacent nodes via a link having a cost value to an end node that is a node other than the node among the plurality of nodes. A route determination method,
A process of selecting each of the plurality of nodes as a starting point node;
Processing for recognizing the selected start point node as the end point node of the determined shortest path;
The communication path from the start node to the undecided node that is adjacent to the end node of the determined shortest path and whose shortest path from the start node is an undecided node is the shortest candidate for the shortest path. The shortest path candidate having the lowest cost value is determined as the shortest path among the shortest path candidates, and the end node of the determined shortest path is recognized as the end node of the determined shortest path. Instead of the existing node, a determination process that repeats newly recognizing as an end node of the determined shortest path, and
In the determination process, a communication path from the start point node to an undecided node having a minimum cost value set to a link between the undecided node and an end point node of the determined shortest path is A route determination method for selecting a shortest route candidate. In the route determination method according to claim 3,
For each of the plurality of nodes, further includes processing for generating in advance cost order information, which is information in which communication paths to nodes adjacent to the node are arranged in order of increasing cost values,
In the determination process, in the cost order information of the end node of the determined shortest path, the determined shortest path is added to the highest communication path excluding the communication path to the node on the determined shortest path. In the cost order information of the parent node which is a node adjacent to the end node of the determined shortest path on the determined shortest path and the end node of the determined shortest path on the start point node side on the determined shortest path A communication path obtained by adding a communication path from the start point node to the parent node among the determined shortest paths to the highest communication path excluding a communication path to a node on the path, the shortest path candidate The route determination method.