TypeError: unsupported operand type(s) for /: 'tuple' and 'int' during stats.compile for DEAP

[Robin Müller-Bady]

Dear all,

I got a problem using the module and the stats module. Maybe one of the experienced users may help me with that.

Before: I'm using the module since more than 2 years, this is the first time this error occurs (therefore I think it comes from my side).

I'm creating an EA using DEAP 1.1. Individuals consist of Integer lists, where each element may be 0 or 1. The population itself is again a list.

Now, I create stats with the following elements:

stats = tools.Statistics(key=lambda ind: ind.fitness.values)
time_start = time.time()

def timecap(ind):
 return time.time() - time_start

stats.register("avg", np.mean)
stats.register("med", np.median)
stats.register("std", np.std)
stats.register("min", np.min)
stats.register("max", np.max)
stats.register("time", timecap)

Occasionally (sometimes after 1,000,000 evaluations / 200 generations, sometimes right after the start with the initial population), the following error occurs:

  File "/home/robin/workspace/untitled/monitor_selection.py", line 219, in EA
    record = stats.compile(population) if stats is not None else {}
  File "/usr/local/lib/python3.5/dist-packages/deap-1.1.0-py3.5-linux-x86_64.egg/deap/tools/support.py", line 208, in compile
    entry[key] = func(values)
  File "/usr/local/lib/python3.5/dist-packages/numpy/core/fromnumeric.py", line 2992, in std
    keepdims=keepdims)
  File "/usr/local/lib/python3.5/dist-packages/numpy/core/_methods.py", line 124, in _std
    keepdims=keepdims)
  File "/usr/local/lib/python3.5/dist-packages/numpy/core/_methods.py", line 94, in _var
    arrmean, rcount, out=arrmean, casting='unsafe', subok=False)
TypeError: unsupported operand type(s) for /: 'tuple' and 'int'

I tried to debug the code using PyCharms debugger, but unfortunately I can't find an error in my code (especially when it runs in most cases).

Do you have any idea?

Thank you very much in advance!

[François-Michel De Rainville]

My first guess is that, for an unknown reason, you are giving an empty population to stats.compile.

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[Robin Müller-Bady]

Unfortunately, this is not the case. The population is present (I see the instances with my debugger).

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[François-Michel De Rainville]

Using pdb I think you can add an instruction to start debugger on exception. You could then get a full stack trace and find what tuple cannot be divided by an integer.

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[Robin Müller-Bady]

Thank you very much. I found out that, for reasons yet unknown, one individual of my population is not evaluated. I don't know about your software engineering, but an error handling like follows could help debugging (at least for me :-) ):

in module deap/tools/support.py

def compile(self, data):
    """Apply to the input sequence *data* each registered function
    and return the results as a dictionnary.


    :param data: Sequence of objects on which the statistics are computed.
    """
    values = tuple(self.key(elem) for elem in data)
    assert all(values), "Error: not all values are evaluated!"
    entry = dict()
    for key, func in self.functions.items():
        entry[key] = func(values)
    return entry

However, the program crashes again, but at least you know why :-)

Best regards,
Robin

[François-Michel De Rainville]

Thanks, we will look into adding an assertion like proposed.

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