Count and Ratio Constraints

An optimization model is a representation of the reality and the goal is to get it as close as possible, while ignoring as many details as you can. One of the specific business rules which can not always be ignored are constraints with respect to certain counts and ratios. For instance, each of the products can only be stored in 3 warehouses or 50% of my supply needs to be sourced from Europe. In the upcoming releases we will be gradually adding some count and ratio constraints to the model.

The remainder of this section describes the constraints which are already available or which are to be introduced in the upcoming releases.

Count Constraints

These constraints can be used to model business rules which impose minimum or maximum restrictions on the number of resources or locations which can be opened. SC Navigator currently contains the following count constraints (see attribute details at Count Constraint Attributes):

Location Product: This enforces a constraint on the minimum or the maximum number of locations (from a given group of locations) where at least one product (or product from a given product group) is active.

Resource Count: This enforces a constraint on the minimum or the maximum number of locations (from a given location group) where at least one resource (from a given resource group) is active.

The following count constraints will become available in future versions of SC Navigator (note that the attributes Minimum # of Source/Destination Locations are already captured by the model, see Optimization Parameters and Constraints):

Minimum # of Source Locations: This enforces a minimum number of source locations per product and period which serve a customer or warehouse/production facility;

Minimum # of Destination Locations: This enforces a minimum number of destination locations per product and period which the supplier/production/warehouse facility serves;

Minimum/Maximum Inflow from Source Locations: This enforce a minimum/maximum number of products which are sent from a source location to a customer or to a production/warehouse location;

Minimum/Maximum Outflow to Destination Locations: This enforces a minimum/maximum number of products which are sent from a supplier/production/warehouse location to a destination location.

Ratio Constraints

These constraints can be used to model business rules which impose restrictions on the contribution that should be made by certain suppliers or resources. For example, it may be important that no supplier is responsible for providing more than x % of a raw material, or road transport cannot exceed y % of total transportation between two locations or location groups. SC Navigator contains the following ratio constraints (see attribute details at Ratio Constraint Attributes):

Supplier Ratio: This enforces a minimum or a maximum ratio of the contribution of a supplier (or supplier group) compared to the total supply;

Production Ratio: This enforces a minimum or a maximum ratio for a production resource (or a group of productions) compared to the total production amount;

Warehouse Ratio: This enforces a minimum or a maximum ratio for a warehouse (or a group of warehouses) with respect to throughput, inflow, or outflow;

Transport Ratio: This enforces transport lanes to carry a particular ratio of the total in/out flow for locations or resources. For instance, inbound transport to a DC must be at least 70% by road and 30% by rail.