- 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.
+ Return a feasible starting point for player one.
+
+ This starting point is for the CVXOPT formulation and not for
+ the original game. The basic premise is that if you normalize
+ :meth:`e2`, then you get a point in :meth:`K` that makes a unit
+ inner product with :meth:`e2`. We then get to choose the primal
+ objective function value such that the constraint involving
+ :meth:`L` is satisfied.
+ """
+ p = self.e2() / (norm(self.e2()) ** 2)
+
+ # Compute the distance from p to the outside of K.
+ if isinstance(self.K(), NonnegativeOrthant):
+ # How far is it to a wall?
+ dist = min(list(self.e1()))
+ elif isinstance(self.K(), IceCream):
+ # How far is it to the boundary of the ball that defines
+ # the ice-cream cone at a given height? Now draw a
+ # 45-45-90 triangle and the shortest distance to the
+ # outside of the cone should be 1/sqrt(2) of that.
+ # It works in R^2, so it works everywhere, right?
+ height = self.e1()[0]
+ radius = norm(self.e1()[1:])
+ dist = (height - radius) / sqrt(2)
+ else:
+ raise NotImplementedError
+
+ nu = - specnorm(self.L())/(dist*norm(self.e2()))
+ x = matrix([nu,p], (self.dimension() + 1, 1))
+ s = - self._G()*x
+
+ return {'x': x, 's': s}
+
+
+ def player2_start(self):
+ """
+ Return a feasible starting point for player two.
+ """
+ q = self.e1() / (norm(self.e1()) ** 2)
+
+ # Compute the distance from p to the outside of K.
+ if isinstance(self.K(), NonnegativeOrthant):
+ # How far is it to a wall?
+ dist = min(list(self.e2()))
+ elif isinstance(self.K(), IceCream):
+ # How far is it to the boundary of the ball that defines
+ # the ice-cream cone at a given height? Now draw a
+ # 45-45-90 triangle and the shortest distance to the
+ # outside of the cone should be 1/sqrt(2) of that.
+ # It works in R^2, so it works everywhere, right?
+ height = self.e2()[0]
+ radius = norm(self.e2()[1:])
+ dist = (height - radius) / sqrt(2)
+ else:
+ raise NotImplementedError
+
+ omega = specnorm(self.L())/(dist*norm(self.e1()))
+ y = matrix([omega])
+ z2 = q
+ z1 = y*self.e2() - self.L().trans()*z2
+ z = matrix([z1,z2], (self.dimension()*2, 1))
+
+ return {'y': y, 'z': z}