calling external code: conditional depends on variable not in constraints

Again related to #590, I’d like to do this:

from gpkit import VectorVariable, Variable, units, SignomialProgram
import gpkit
from gpkit.constraints.set import ConstraintSet

Re = Variable("Re", 1e5, "-", "Reynolds Number")
CL = Variable("C_L", "-", "Lift Coefficient")
CD = Variable("C_D", "-", "Drag Coefficient")


def xfoil(x0):
    return [CD >= 0.01 + .03*CL**2]

class AeroModel(ConstraintSet):
    def as_gpconstr(self, x0):
        gpconstr = super(AeroModel, self).as_gpconstr(x0)
        if x0 and x0["Re"] >= 1e6:
            constraints = xfoil(x0)
        else:
            constraints = [CD >= 1. + CL**2]
        return ConstraintSet([gpconstr, constraints])

constraints = AeroModel([CL >= 1.0])

objective = CD

m = SignomialProgram(objective, constraints, require_signomial=False)
m.localsolve('cvxopt', verbosity=1)

But I’m getting:

Beginning signomial solve.
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-5-0f0a49bf286c> in <module>()
     25 
     26 m = SignomialProgram(objective, constraints, require_signomial=False)
---> 27 m.localsolve('cvxopt', verbosity=1)

/Users/codykarcher/Dropbox (MIT)/Research/gpkit/gpkit/constraints/signomial_program.py in localsolve(self, solver, verbosity, x0, rel_tol, iteration_limit, **kwargs)
    105     appear to be converging, you may wish to increase the iteration limit by
    106     calling .localsolve(..., iteration_limit=NEWLIMIT).""" % len(self.gps))
--> 107             gp = self.gp(x0, verbosity=verbosity-1)
    108             self.gps.append(gp)  # NOTE: SIDE EFFECTS
    109             try:

/Users/codykarcher/Dropbox (MIT)/Research/gpkit/gpkit/constraints/signomial_program.py in gp(self, x0, verbosity)
    134     def gp(self, x0=None, verbosity=1):
    135         """Get a GP approximation of this SP at x0"""
--> 136         return GeometricProgram(self.cost, self.as_gpconstr(x0),
    137                                 self.substitutions, verbosity=verbosity)

/Users/codykarcher/Dropbox (MIT)/Research/gpkit/gpkit/constraints/set.py in as_gpconstr(self, x0)
    165 
    166         When x0 is none, may return a default guess."""
--> 167         cs = ConstraintSet([constr.as_gpconstr(x0) for constr in self])
    168         cs.substitutions.update(self.substitutions)
    169         return cs

<ipython-input-5-0f0a49bf286c> in as_gpconstr(self, x0)
     14     def as_gpconstr(self, x0):
     15         gpconstr = super(AeroModel, self).as_gpconstr(x0)
---> 16         if x0 and x0["Re"] >= 1e6:
     17             constraints = xfoil(x0)
     18         else:

/Users/codykarcher/Dropbox (MIT)/Research/gpkit/gpkit/keydict.pyc in __getitem__(self, key)
     94         keys = self.keymap[key]
     95         if not keys:
---> 96             raise KeyError("%s was not found." % key)
     97         values = []
     98         for key in keys:

KeyError: 'Re was not found.'

I’d like to be able to pass in the constants, but apparently they aren’t in the x0 vector? Thoughts?

Note, the example as defined in #590 works fine.

[whoburg]

related to #590

[bqpd]

@cjk12, what’s the current status of this problem?