Arrays

An array is a grid of values that belongs to the whole model, for when a single variable is not enough: a table of setup times, a matrix of travel distances between locations, a price list by product number. Like a variable an array is global; unlike a variable it holds many values that you reach by position.

Define arrays in the Logic Builder, on the Arrays tab.

Defining an array

• Name: prefixed r_, for example r_SetupTime.
• Type: Integer, Real, Date, or Descriptive.
• Dimensions: an array can be one, two, or three dimensional. Set the size of each dimension you use and leave the others at zero: a single row of ten is 10, a ten-by-five grid is 10 × 5.
• Initial: a starting value applied to every cell.
• Statistics: track how the cells change during the run for the Arrays report.

You can also import an array’s contents from a file (Excel or CSV) instead of typing them in, which is the easy way to load a large lookup table.

Using an array

Read or write a cell by its position in logic and expressions, for example a setup time looked up by the product number.

You can also step a single cell up or down in place with INC and DEC, the same way you would a counter variable. INC r_Array1[5] adds one to the fifth cell and DEC r_Array1[5] takes one away, so a running tally can live in an array indexed by type or by location without reading the cell, adding, and writing it back.

Worked examples

Setup time by product

A single row indexed by product number returns a machine’s setup time without a chain of IF tests. Fill r_SetupTime once, then read the cell for the entity’s product:

SET a_Setup TO r_SetupTime[a_Product]
TIME a_Setup min

A travel-distance matrix

A two-dimensional array is a grid, so r_Distance[from, to] holds the distance between any two locations and one array covers every pair:

SET a_Miles TO r_Distance[a_From, a_To]
TIME a_Miles / v_Speed hr

A price list by product number

Keep unit prices in r_Price and multiply by the quantity the entity carries. Editing the table reprices the model without touching any logic:

SET a_Price TO r_Price[a_Product]
SET a_LineTotal TO a_Price * a_Qty

A running tally

Step one cell in place to keep a live count per location. Add on the way in and take away on the way out, and the array holds work in progress without reading, adding, and writing it back:

// as an entity enters a location
INC r_WIP[a_Loc]

// as it leaves
DEC r_WIP[a_Loc]

The Arrays report

After a run, the Arrays report shows each array’s size, how many cells were used, and its value range, with a drill-down into the contents and their changes.