Information processing system and method of information processing

An information processing system comprising:

• a hardware processor configured to:
• obtain a supply chain network in which a plurality of nodes each corresponding to one of a plurality of companies are connected together through links each representing a trading relationship in which a supply source company of a product is associated with a supply destination company of the product;
• extract, from the supply chain network, a subnetwork including at least one of an upstream subnetwork and a downstream subnetwork, the upstream subnetwork including an upstream company that supplies the product to a company corresponding to a processing target node among the plurality of companies, the downstream subnetwork including a downstream company that is supplied with the product from the company corresponding to the processing target node;
• determine a complex vector representing the processing target node by assigning, to each of the plurality of nodes included in the subnetwork of the processing target node, a complex number having a phase corresponding to a distance to the processing target node, and having an absolute value corresponding to an amount of flow going to or coming from the processing target node;
• and
• calculate a similarity between two of the plurality of nodes in accordance with the two complex vectors corresponding to the two nodes, wherein
• the plurality of nodes includes first to nth nodes, where n is an integer equal to or greater than two,
• the complex vector corresponding to an ith node is defined as xi, where i is an integer satisfying 1≤i≤n,
• a number of the plurality of nodes is in the order of thousands or more, and
• the hardware processor is configured to:
• determine a matrix X=[x1, x2, . . . , xn] in which the complex vectors corresponding to the first to nth nodes are arranged, and a matrix X* in which conjugate complex numbers of individual elements of the matrix X are transposed, and to determine a complex correlation matrix C through C=XX*;
• and
• infer a main path in the supply chain network by subjecting the complex correlation matrix C to eigenvalue decomposition.