ExitConditionsError on model solve

[yanivabir]

Hello,

I'm trying to solve a model with drift rate linearly dependent on coherence, and exponentially collapsing bounds.

Under some parameter values x coherence combinations, I get the following error (including parameter values that were fit to the data, and a coherence value that existed in the data):

ExitConditionsError: Ensures statement 'solution.prob_undecided() <= return.prob_undecided()' failed in OverlayNonDecision.apply
params: {'self': OverlayNonDecision(nondectime=0.1969366668762308), 'solution': <ddm.solution.Solution object at 0x7fc6a13c6ee0>, 'return': <ddm.solution.Solution object at 0x7fc6a13c6bb0>}

What does this error mean, and what should I do?

Thanks!
Yaniv

[mwshinn]

Hi Yaniv,

Could you please post some code which reproduces the error? Also, please include the full error you receive.

[yanivabir]

Of course!

This is the code that produces the error:

from ddm import Model, Sample
from ddm.models import DriftConstant, NoiseConstant, BoundCollapsingExponential, OverlayNonDecision
import ddm.models

class DriftCoherence(ddm.models.Drift):
    name = "Drift depends linearly on coherence"
    required_parameters = ["drift_coh"] 
    required_conditions = ["coh"] 

    # We must always define the get_drift function, which is used to compute the instantaneous value of drift.
    def get_drift(self, conditions, **kwargs):
        return self.drift_coh * conditions['coh']


model = Model(name='Simple model fit w/ collapsing bounds',
                 drift=DriftCoherence(drift_coh=2.40942458),
                 noise=NoiseConstant(noise=1),
                 bound=BoundCollapsingExponential(B = 1.61599993, tau = 0.7969612),
                 overlay=OverlayNonDecision(nondectime=0.17380648),
                 dx=.001, dt=.01, T_dur=5)

model.solve(conditions={"coh": 0.5})

And this is the error message produced:

---------------------------------------------------------------------------

ExitConditionsError                       Traceback (most recent call last)

<ipython-input-6-ac8df8241f5c> in <module>()
     20                  dx=.001, dt=.01, T_dur=5)
     21 
---> 22 model.solve(conditions={"coh": 0.5})

4 frames

/usr/local/lib/python3.7/dist-packages/paranoid/decorators.py in _check_ensures(func, returnvalue, argvals)
     87                     if not eval(ensurement, limited_globals, {}):
     88                         env_simp = {k.replace(_BT, '`').replace(_RET, 'return'): v for k,v in env.items()}
---> 89                         raise E.ExitConditionsError("Ensures statement '%s' failed in %s\nparams: %s" % (etext, func.__qualname__, str(env_simp)))
     90         # Update the cache
     91         if any(btdepth>0 for btdepth,_,_ in U.get_fun_prop(func, "ensures")) : # Cache if we refer to previous executions

ExitConditionsError: Ensures statement 'solution.prob_undecided() <= return.prob_undecided()' failed in OverlayNonDecision.apply
params: {'self': OverlayNonDecision(nondectime=0.17380648), 'solution': <ddm.solution.Solution object at 0x7f21e76bb750>, 'return': <ddm.solution.Solution object at 0x7f21e776aed0>}

[mwshinn]

Thanks for reporting the bug. I just pushed a fix in commit 0647eef.

As a workaround, you can run this at the beginning of your file:

import paranoid; paranoid.settings.Settings.set(enabled=False)

[yanivabir]

thanks!