Ten candidate alternatives and eight objects form a real, textbook-sourced set-covering instance the external solver reads, parsed from its model file. At ten alternatives the small coverage grid no longer fits, so tables replace it.
highlighted = computed this step
The instance
There are 10 candidate alternatives and 8 objects, parsed from the solver's model file at build time, not hand-typed. Why: real set-covering instances name each candidate's cost and coverage independently — this one is drawn from a real textbook (Lundgren, Roennqvist, Vaebrand's textbook 'Optimeringslaera' ('Optimization theory'), via OR-Tools' own contrib set-covering example code).
alternatives=10
No small grid
The earlier chapters' instance had 4 candidate sites, small enough for a coverage grid to draw by hand; at 10 alternatives the table above replaces the grid. Why: the coverage relationships are still exact — only the picture changes, not the arithmetic.
ten alternatives, no small grid
The objective
The model minimizes total cost over the chosen alternatives, each costing between 13 and 19. Why: this lesson only presents the instance; solving, with its certificate, comes next.
min∑cixi,xi∈{0,1}
Diagram note
The first table marks a 1 wherever an alternative covers an object, one row per object; the second lists each alternative's cost. Pixel positions are rounded for layout; every displayed coverage, cost, and comparison is exact.