def set_up(sets, propagate, smallest_first):
""" Set up the solver and All_Different for the transversals problem. """
Solver_FD.set_up()
# Create a Var_FD for each set. Its initial range is the entire set.
vars = {Var_FD(s.domain) for s in sets}
All_Different(vars)
trace = propagate and smallest_first
solver_fd = Solver_FD(vars,
propagate=propagate,
smallest_first=smallest_first,
trace=trace)
if solver_fd.trace:
print(f'{"~" * 90}\n')
print('Following is the trace of the final search.')
print(Solver_FD.to_str(sets))
print(f'propagate: {propagate}; smallest_first: {smallest_first};\n')
return solver_fd
The search is a standard depth-first search with two heuristics: propagate
and smallest_first.
The search is done four time with different settings of propagate and smallest-first.
When propagate is true, once an element is selected as the representative of one set,
it is removed from consideration as a posible representative of other sets.
When smallest-first is true, the search selectes an element for an unrepresented set
by chosing the smallest unrepresented set to find a representative for.
When both propagate and smallest_first are true, a trace of the search is shown.
""")
print('The sets for which to find a traversal are:\n',
Solver_FD.to_str(sets), '\n')
print('The (alphabetized) traversals are:')
for propagate in [False, True]:
for smallest_first in [False, True]:
solver_fd = set_up(sets,
propagate=propagate,
smallest_first=smallest_first)
sol_str_set = set()
if solver_fd.trace:
print(
'*: Var was directly instantiated--and propagated if propagation is on.\n'
'-: Var was indirectly instantiated but not propagated.\n')
assert solver_fd.propagate == propagate and solver_fd.smallest_first == smallest_first
for _ in solver_fd.solve():