This project was created to demonstrate a simple example of using HTN planning. The planner implementation used is Pyhop
https://bitbucket.org/dananau/pyhop
Our goal is to build a small town. Number of buildings is defined by us by declaring tasks in 'build_town' complex task
def build_town(state):
print state
return [('build_barracks_task',),('build_watchtower_task',)]There are 2 types of resources:
- gold
- wood
There are 3 types of buildings:
- barracks
- watchtower
- house
There are workers (peons), who require resources and free spaces in houses. If there are no free places then a house must be built
Each building cost along with workers are defined in methods.py file. You can manipulate it to see what will be the output for different parameters.
The initial state (peons, gold, wood, free places) is defined in htn.py file
To run the algorithm enter
python htn.pyTo see all methods and operators see file methods.py
Example code explained.
def build_house_task_a(state):
if state.gold >= HOUSE_COST_GOLD:
return [('build_house',)]
else:
return False
def build_house_task_b(state):
if state.gold < HOUSE_COST_GOLD:
return [('gather_gold_task',),('build_house_task',)]
else:
return False
pyhop.declare_methods('build_house_task',build_house_task_a,build_house_task_b)
def build_house(state):
if state.gold >= HOUSE_COST_GOLD:
state.gold = state.gold - HOUSE_COST_GOLD
state.free_places = state.free_places + 5
state.houses = state.houses + 1
return state
return FalseThe above code declares a complex task 'build_house_task'. If preconditions are met then 'build_house' action(operator) is called. Otherwise call another complex task 'gather_gold_task' and after that try to return to this task ('build_house_task')
I maintained a naming convention where complex tasks had the _task suffix, while operators hadn't.
Town should hava a barracks and a watchtower
depth 1 tasks [('build_barracks_task',), ('build_watchtower_task',)]
depth 2 tasks [('gather_wood_task',), ('build_barracks_task',), ('build_watchtower_task',)]
depth 3 tasks [('gather_wood',), ('build_barracks_task',), ('build_watchtower_task',)]
depth 4 tasks [('build_barracks_task',), ('build_watchtower_task',)]
depth 5 tasks [('build_barracks',), ('build_watchtower_task',)]
depth 6 tasks [('build_watchtower_task',)]
depth 7 tasks [('train_peon_task',), ('build_watchtower_task',)]
depth 7 tasks [('gather_gold_task',), ('build_watchtower_task',)]
depth 3 tasks [('train_peon_task',), ('gather_wood_task',), ('build_barracks_task',), ('build_watchtower_task',)]
depth 4 tasks [('train_peon',), ('gather_wood_task',), ('build_barracks_task',), ('build_watchtower_task',)]
depth 5 tasks [('gather_wood_task',), ('build_barracks_task',), ('build_watchtower_task',)]
depth 6 tasks [('gather_wood',), ('build_barracks_task',), ('build_watchtower_task',)]
depth 7 tasks [('build_barracks_task',), ('build_watchtower_task',)]
depth 8 tasks [('gather_gold_task',), ('build_barracks_task',), ('build_watchtower_task',)]
depth 9 tasks [('gather_gold',), ('build_barracks_task',), ('build_watchtower_task',)]
depth 10 tasks [('build_barracks_task',), ('build_watchtower_task',)]
depth 11 tasks [('build_barracks',), ('build_watchtower_task',)]
depth 12 tasks [('build_watchtower_task',)]
depth 13 tasks [('build_watchtower',)]
depth 14 tasks []
** result = [('train_peon',), ('gather_wood',), ('gather_gold',), ('build_barracks',), ('build_watchtower',)]