return matrix([1], tc='d')
- def _try_solution(self, tolerance):
- """
- Solve this linear game within ``tolerance``, if possible.
-
- This private function is the one that does all of the actual
- work for :meth:`solution`. This method accepts a ``tolerance``,
- and what :meth:`solution` does is call this method twice with
- two different tolerances. First it tries a strict tolerance, and
- then it tries a looser one.
-
- .. warning::
-
- If you try to be smart and precompute the matrices used by
- this function (the ones passed to ``conelp``), then you're
- going to shoot yourself in the foot. CVXOPT can and will
- clobber some (but not all) of its input matrices. This isn't
- performance sensitive, so play it safe.
- Parameters
- ----------
-
- tolerance : float
- The absolute tolerance to pass to the CVXOPT solver.
+ def solution(self):
+ """
+ Solve this linear game and return a :class:`Solution`.
Returns
-------
Examples
--------
- This game can be solved easily, so the first attempt in
- :meth:`solution` should succeed::
+ This example is computed in Gowda and Ravindran in the section
+ "The value of a Z-transformation"::
>>> from dunshire import *
- >>> from dunshire.matrices import norm
- >>> from dunshire.options import ABS_TOL
>>> K = NonnegativeOrthant(3)
>>> L = [[1,-5,-15],[-1,2,-3],[-12,-15,1]]
>>> e1 = [1,1,1]
>>> e2 = [1,1,1]
>>> SLG = SymmetricLinearGame(L, K, e1, e2)
- >>> s1 = SLG.solution()
- >>> s2 = SLG._try_solution(options.ABS_TOL)
- >>> abs(s1.game_value() - s2.game_value()) < ABS_TOL
- True
- >>> norm(s1.player1_optimal() - s2.player1_optimal()) < ABS_TOL
- True
- >>> norm(s1.player2_optimal() - s2.player2_optimal()) < ABS_TOL
- True
+ >>> print(SLG.solution())
+ Game value: -6.1724138
+ Player 1 optimal:
+ [ 0.551...]
+ [-0.000...]
+ [ 0.448...]
+ Player 2 optimal:
+ [0.448...]
+ [0.000...]
+ [0.551...]
- This game cannot be solved with the default tolerance, but it
- can be solved with a weaker one::
+ The value of the following game can be computed using the fact
+ that the identity is invertible::
>>> from dunshire import *
- >>> from dunshire.options import ABS_TOL
- >>> L = [[ 0.58538005706658102767, 1.53764301129883040886],
- ... [-1.34901059721452210027, 1.50121179114155500756]]
- >>> K = NonnegativeOrthant(2)
- >>> e1 = [1.04537193228494995623, 1.39699624965841895374]
- >>> e2 = [0.35326554172108337593, 0.11795703527854853321]
- >>> SLG = SymmetricLinearGame(L,K,e1,e2)
- >>> print(SLG._try_solution(ABS_TOL / 10))
- Traceback (most recent call last):
- ...
- dunshire.errors.GameUnsolvableException: Solution failed...
- >>> print(SLG._try_solution(ABS_TOL))
- Game value: 9.1100945
+ >>> K = NonnegativeOrthant(3)
+ >>> L = [[1,0,0],[0,1,0],[0,0,1]]
+ >>> e1 = [1,2,3]
+ >>> e2 = [4,5,6]
+ >>> SLG = SymmetricLinearGame(L, K, e1, e2)
+ >>> print(SLG.solution())
+ Game value: 0.0312500
Player 1 optimal:
- [-0.0000000]
- [ 8.4776631]
+ [0.031...]
+ [0.062...]
+ [0.093...]
Player 2 optimal:
- [0.0000000]
- [0.7158216]
+ [0.125...]
+ [0.156...]
+ [0.187...]
+
+ This is another Gowda/Ravindran example that is supposed to have
+ a negative game value::
+
+ >>> from dunshire import *
+ >>> from dunshire.options import ABS_TOL
+ >>> L = [[1, -2], [-2, 1]]
+ >>> K = NonnegativeOrthant(2)
+ >>> e1 = [1, 1]
+ >>> e2 = e1
+ >>> SLG = SymmetricLinearGame(L, K, e1, e2)
+ >>> SLG.solution().game_value() < -ABS_TOL
+ True
+
+ Tests
+ -----
+
+ The following two games are problematic numerically, but we
+ should be able to solve them::
+
+ >>> from dunshire import *
+ >>> L = [[-0.95237953890954685221, 1.83474556206462535712],
+ ... [ 1.30481749924621448500, 1.65278664543326403447]]
+ >>> K = NonnegativeOrthant(2)
+ >>> e1 = [0.95477167524644313001, 0.63270781756540095397]
+ >>> e2 = [0.39633793037154141370, 0.10239281495640320530]
+ >>> SLG = SymmetricLinearGame(L, K, e1, e2)
+ >>> print(SLG.solution())
+ Game value: 18.767...
+ Player 1 optimal:
+ [-0.000...]
+ [ 9.766...]
+ Player 2 optimal:
+ [1.047...]
+ [0.000...]
+
+ ::
+
+ >>> from dunshire import *
+ >>> L = [[1.54159395026049472754, 2.21344728574316684799],
+ ... [1.33147433507846657541, 1.17913616272988108769]]
+ >>> K = NonnegativeOrthant(2)
+ >>> e1 = [0.39903040089404784307, 0.12377403622479113410]
+ >>> e2 = [0.15695181142215544612, 0.85527381344651265405]
+ >>> SLG = SymmetricLinearGame(L, K, e1, e2)
+ >>> print(SLG.solution())
+ Game value: 24.614...
+ Player 1 optimal:
+ [ 6.371...]
+ [-0.000...]
+ Player 2 optimal:
+ [2.506...]
+ [0.000...]
"""
try:
- opts = {'show_progress': options.VERBOSE, 'abstol': tolerance}
+ opts = {'show_progress': options.VERBOSE}
soln_dict = solvers.conelp(self._c(),
self._G(),
self._h(),
# The "status" field contains "optimal" if everything went
# according to plan. Other possible values are "primal
# infeasible", "dual infeasible", "unknown", all of which mean
- # we didn't get a solution. The "infeasible" ones are the
- # worst, since they indicate that CVXOPT is convinced the
- # problem is infeasible (and that cannot happen).
+ # we didn't get a solution.
+ #
+ # The "infeasible" ones are the worst, since they indicate
+ # that CVXOPT is convinced the problem is infeasible (and that
+ # cannot happen).
if soln_dict['status'] in ['primal infeasible', 'dual infeasible']:
raise GameUnsolvableException(self, soln_dict)
- elif soln_dict['status'] == 'unknown':
- # When we get a status of "unknown", we may still be able
- # to salvage a solution out of the returned
- # dictionary. Often this is the result of numerical
- # difficulty and we can simply check that the primal/dual
- # objectives match (within a tolerance) and that the
- # primal/dual optimal solutions are within the cone (to a
- # tolerance as well).
- #
- # The fudge factor of two is basically unjustified, but
- # makes intuitive sense when you imagine that the primal
- # value could be under the true optimal by ``ABS_TOL``
- # and the dual value could be over by the same amount.
- #
- if abs(p1_value - p2_value) > tolerance:
- raise GameUnsolvableException(self, soln_dict)
- if (p1_optimal not in self._K) or (p2_optimal not in self._K):
- raise GameUnsolvableException(self, soln_dict)
-
- return Solution(p1_value, p1_optimal, p2_optimal)
-
- def solution(self):
- """
- Solve this linear game and return a :class:`Solution`.
-
- Returns
- -------
-
- :class:`Solution`
- A :class:`Solution` object describing the game's value and
- the optimal strategies of both players.
-
- Raises
- ------
- GameUnsolvableException
- If the game could not be solved (if an optimal solution to its
- associated cone program was not found).
-
- PoorScalingException
- If the game could not be solved because CVXOPT crashed while
- trying to take the square root of a negative number.
-
- Examples
- --------
-
- This example is computed in Gowda and Ravindran in the section
- "The value of a Z-transformation"::
-
- >>> from dunshire import *
- >>> K = NonnegativeOrthant(3)
- >>> L = [[1,-5,-15],[-1,2,-3],[-12,-15,1]]
- >>> e1 = [1,1,1]
- >>> e2 = [1,1,1]
- >>> SLG = SymmetricLinearGame(L, K, e1, e2)
- >>> print(SLG.solution())
- Game value: -6.1724138
- Player 1 optimal:
- [ 0.551...]
- [-0.000...]
- [ 0.448...]
- Player 2 optimal:
- [0.448...]
- [0.000...]
- [0.551...]
-
- The value of the following game can be computed using the fact
- that the identity is invertible::
+ # The "optimal" and "unknown" results, we actually treat the
+ # same. Even if CVXOPT bails out due to numerical difficulty,
+ # it will have some candidate points in mind. If those
+ # candidates are good enough, we take them. We do the same
+ # check (perhaps pointlessly so) for "optimal" results.
+ #
+ # First we check that the primal/dual objective values are
+ # close enough (one could be low by ABS_TOL, the other high by
+ # it) because otherwise CVXOPT might return "unknown" and give
+ # us two points in the cone that are nowhere near optimal.
+ if abs(p1_value - p2_value) > 2*options.ABS_TOL:
+ raise GameUnsolvableException(self, soln_dict)
- >>> from dunshire import *
- >>> K = NonnegativeOrthant(3)
- >>> L = [[1,0,0],[0,1,0],[0,0,1]]
- >>> e1 = [1,2,3]
- >>> e2 = [4,5,6]
- >>> SLG = SymmetricLinearGame(L, K, e1, e2)
- >>> print(SLG.solution())
- Game value: 0.0312500
- Player 1 optimal:
- [0.031...]
- [0.062...]
- [0.093...]
- Player 2 optimal:
- [0.125...]
- [0.156...]
- [0.187...]
+ # And we also check that the points it gave us belong to the
+ # cone, just in case...
+ if (p1_optimal not in self._K) or (p2_optimal not in self._K):
+ raise GameUnsolvableException(self, soln_dict)
- """
- try:
- # First try with a stricter tolerance. Who knows, it might
- # work. If it does, we prefer that solution.
- return self._try_solution(options.ABS_TOL / 10)
-
- except (PoorScalingException, GameUnsolvableException):
- # Ok, that didn't work. Let's try it with the default tolerance..
- try:
- return self._try_solution(options.ABS_TOL / 10)
- except (PoorScalingException, GameUnsolvableException) as error:
- # Well, that didn't work either. Let's verbosify the matrix
- # output format before we allow the exception to be raised.
- printing.options['dformat'] = options.DEBUG_FLOAT_FORMAT
- raise error
+ # For the game value, we could use any of:
+ #
+ # * p1_value
+ # * p2_value
+ # * (p1_value + p2_value)/2
+ # * the game payoff
+ #
+ # We want the game value to be the payoff, however, so it
+ # makes the most sense to just use that, even if it means we
+ # can't test the fact that p1_value/p2_value are close to the
+ # payoff.
+ payoff = self.payoff(p1_optimal,p2_optimal)
+ return Solution(payoff, p1_optimal, p2_optimal)
def condition(self):
projects / dunshire.git / blobdiff