Intermittent "Fatal Python error: Cannot recover from stack overflow." from wester tests on Travis

[asmeurer]

sympy/core/tests/test_wester.py[397] ........ffffffffffffffffffffffffffffffffffX
wffwXffffffffffffffffffffffffffffffffffffffffffffffffffffffffffXffffffffffffffff
fXXfXfXfffFatal Python error: Cannot recover from stack overflow.
Current thread 0x00007fd7f1d55700:
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in is_number
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in <genexpr>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in is_number
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in <genexpr>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in is_number
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in <genexpr>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in is_number
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in <genexpr>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 360 in is_number
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 1259 in _eval_is_prime
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 290 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 302 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 247 in getit
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 1107 in _eval_is_imaginary
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 290 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 302 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 302 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 302 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 302 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 247 in getit
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/add.py", line 530 in _eval_is_irrational
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 290 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 302 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 247 in getit
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 1082 in _eval_real_imag
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 1072 in _eval_is_real
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 290 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 247 in getit
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/functions/elementary/integers.py", line 25 in eval
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 225 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 401 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 314 in _eval_power
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 227 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 430 in flatten
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/operations.py", line 41 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 141 in __mul__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/decorators.py", line 118 in binary_op_wrapper
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/decorators.py", line 77 in __sympifyit_wrapper
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 818 in _eval_expand_power_base
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 632 in _eval_power
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 227 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1160 in do
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1184 in <listcomp>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1184 in do
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1164 in <listcomp>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1164 in do
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1188 in factor_terms
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/functions/elementary/complexes.py", line 601 in eval
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 225 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 401 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/functions/elementary/exponential.py", line 666 in as_real_imag
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/functions/elementary/complexes.py", line 78 in eval
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 225 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 401 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 753 in as_real_imag
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/evalf.py", line 1447 in _to_mpmath
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 494 in <listcomp>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 494 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/evalf.py", line 1415 in _evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 1022 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/operations.py", line 342 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 651 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/operations.py", line 342 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/evalf.py", line 1415 in _evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 1022 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/operations.py", line 342 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 651 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/evalf.py", line 1441 in _to_mpmath
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 494 in <listcomp>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 494 in _eval_evalf
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 741 in _eval_is_negative
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 290 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 302 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 302 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 247 in getit
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 1080 in _eval_real_imag
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 1072 in _eval_is_real
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 290 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 247 in getit
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/add.py", line 470 in _eval_is_imaginary
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 290 in _ask
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/assumptions.py", line 247 in getit
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/functions/elementary/integers.py", line 25 in eval
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 225 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/function.py", line 401 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 314 in _eval_power
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 227 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 430 in flatten
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/operations.py", line 41 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/expr.py", line 141 in __mul__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/decorators.py", line 118 in binary_op_wrapper
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/decorators.py", line 77 in __sympifyit_wrapper
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 818 in _eval_expand_power_base
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/mul.py", line 632 in _eval_power
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/power.py", line 227 in __new__
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1160 in do
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1184 in <listcomp>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1184 in do
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1164 in <listcomp>
  File "/home/travis/virtualenv/python3.3.5/lib/python3.3/site-packages/sympy-1.0.1.dev0-py3.3.egg/sympy/core/exprtools.py", line 1164 in do
  ...
Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
Exception: Tests failed

For example, at https://travis-ci.org/sympy/sympy/jobs/136763509. I've also seen it in Python 3.5.

[asmeurer]

I haven't been able to reproduce this locally, even with the same PYTHONHASHSEED and so on. It may be Linux only (I only tested on OS X).

[jksuom]

Is is possible to find out how much memory is allocated for the virtual machines running the Travis jobs?

[asmeurer]

I don't see any information about that in the logs. If there is a Linux command that shows the total memory, you can create .travis.yml that runs that command and look at the output.

[jksuom]

This would probably suffice:

free (1)             - Display amount of free and used memory in the system

[asmeurer]

Would also be useful to run the tests with -v to see exactly what test this is that's crashing Python.

By the way, this error has happened before, which ended up being a bug in Python.

[jksuom]

I'm beginning to suspect that this is caused by a bug in SymPy. The failing test is (most probably) test_W26 in wester.py. The integral is handled by meijerint. It wants to evaluate polar_lift(cos(pi*exp_polar(I*pi)/2)), and therefore it needs to compute sqrt(cos(pi*exp_polar(I*pi)/2)**2). Though this appears trivial on the surface, it does easily lead to RuntimeError: maximum recursion depth exceeded when run manually.

[asmeurer]

There is indeed a RecursionError in SymPy, but the issue is that this shouldn't crash Python. It should be caught by the interpreter. Likely the test that is causing this is an XFAIL test.

[asmeurer]

This is the same thing that happened with the aforementioned CPython bug 14537. A recursion error in an XFAIL test triggered a "Python error: Cannot recover from stack overflow."

[jksuom]

There is RuntimeError in Python 2.7 and RecursionError in Python 3.5. That might explain why only 3.5 is affected. Could it be a regression in Python?

[asmeurer]

The example above is in 3.3.5. But I also saw it in a 3.5 build (I'm not able to find it, though. People have a tendency to just restart builds when they fail, so intermittent failures like this one go unfixed for a long time.)

[jksuom]

I have modified the meijerint lookup table in #11283 so that the polar_lift call would be avoided. This should (hopefully) enable test_W26 to finish with no exception (though not necessarily with the expected result). The bug in sqrt(cos(pi*exp_polar(I*pi)/2)**2) should be fixed independently of this.

[asmeurer]

Haven't seen this in a while. I'm assuming it was fixed.