cpowell/cppgoap

A simple GOAP (goal-oriented action planner) useful for game AI

cppgoap's Issues

Not finding lowest cost path

So, let's say that we have 3 actions:

• chopLogs
  • cost: 4
  • preconditions:
    • hasAxe: true
  • effects:
    • hasWood: true
• getAxe
  • cost: 1
  • preconditions:
  • effects:
    • hasAxe: true
• collectBranches
  • cost: 8
  • preconditions:
  • effects:
    • hasWood: true

Our goal is to get wood, so:

• hasWood: true

And our world state is something like this:

• hasWood: false
• hasAxe: false

And the planner will choose collectBranches (cost: 8) over getAxe, chopLogs (cost: 5)

Doesn't discriminate on action cost?

If there's two actions with the same preconditions and effects but different costs, it doesn't choose the cheapest option. Instead it seems to choose the first option in the Actions vector.

From the war_game example (with typo fixed in scoutRunning):

  Action scout("scoutStealthily", 999);
  scout.setPrecondition(enemy_sighted, false);
  scout.setPrecondition(weapon_in_hand, true);
  scout.setEffect(enemy_sighted, true);
  actions.push_back(scout);

  Action run("scoutRunning", 15);
  run.setPrecondition(enemy_sighted, false);
  run.setPrecondition(weapon_in_hand, true);
  run.setEffect(enemy_sighted, true);
  actions.push_back(run);

As both actions do the same thing but scoutRunning costs less, I'd expect it to be selected - but instead scoutStealthily is always selected regardless of the costs! And if I put actions.push_back(scout) after actions.push_back(run) then scoutRunning is always selected regardless of the costs.

(I've spent the evening implementing multi-dimensional costs, so scoutStealthily can be slow and safe and scoutRunning can be fast but risky, and the agent can be configured to put more weight on the time cost vs the risk cost (vs the ammo cost vs the health cost... etc). But this error occurs with the code as provided.)