Make VectorArrays iterable

[sdrave]

Fixes #1056.

[pmli]

Should also BlockVectorArray and MPIVectorArray be adjusted?

Also, is it possible to test this somehow with hypothesis?

[codecov]

Codecov Report

Merging #1068 into master will decrease coverage by 0.02%.
The diff coverage is 66.66%.

Impacted Files	Coverage Δ
src/pymor/vectorarrays/list.py	83.86% <66.66%> (-0.80%)	⬇️
src/pymor/vectorarrays/numpy.py	84.81% <66.66%> (-0.31%)	⬇️

[sdrave]

Should also BlockVectorArray and MPIVectorArray be adjusted?

Should not be required as IndexError should already be raised when the child arrays are indexed.

Also, is it possible to test this somehow with hypothesis?

I added a simple test.

[sdrave]

@renefritze something bad is happening here with hypothesis. When I add

@reproduce_failure('5.19.0', b'AAAAAgA=')

I get

hypothesis.errors.DidNotReproduce: The shape of the test data has changed in some way from where this blob was defined. Are you sure you're running the same test?

Do you have the same issue?

Also,

py.test --pdb vectorarray.py

stops at

hypothesis.errors.MultipleFailures: Hypothesis found 2 distinct failures.

which is totally useless.

[renefritze]

I can replicate that as is. Maybe it's a bug in your (older) hypothesis version.

r_milk01@29783eb890d5:/pymor$ pytest -k test_iter src/pymortests/vectorarray.py 
============================================================================ test session starts ============================================================================
platform linux -- Python 3.7.8, pytest-6.0.1, py-1.9.0, pluggy-0.13.1
rootdir: /pymor, configfile: setup.cfg
plugins: forked-1.3.0, xdist-2.0.0, cov-2.10.1, pycharm-0.7.0, parallel-0.1.0, timeout-1.4.2, hypothesis-5.28.0, memprof-0.2.0
collected 58 items / 57 deselected / 1 selected                                                                                                                             

src/pymortests/vectorarray.py F                                                                                                                                       [100%]

================================================================================= FAILURES ==================================================================================
_________________________________________________________________________________ test_iter _________________________________________________________________________________

    @pyst.given_vector_arrays()
>   @reproduce_failure('5.28.0', b'AAAAAgA=')
    def test_iter(vector_array):

src/pymortests/vectorarray.py:936: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
/usr/local/lib/python3.7/site-packages/hypothesis/core.py:610: in execute_once
    result = self.test_runner(data, run)
/usr/local/lib/python3.7/site-packages/hypothesis/executors.py:52: in default_new_style_executor
    return function(data)
/usr/local/lib/python3.7/site-packages/hypothesis/core.py:606: in run
    return test(*args, **kwargs)
src/pymortests/vectorarray.py:936: in test_iter
    @reproduce_failure('5.28.0', b'AAAAAgA=')
/usr/local/lib/python3.7/site-packages/hypothesis/core.py:529: in test
    result = self.test(*args, **kwargs)
src/pymortests/vectorarray.py:942: in test_iter
    assert np.all(almost_equal(w, v))
src/pymor/core/defaults.py:236: in defaults_wrapper
    return decorated_function(**kwargs)
src/pymor/algorithms/basic.py:67: in almost_equal
    X -= U
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = NumpyVectorArray([], NumpyVectorSpace(0)), other = NumpyVectorArray([], NumpyVectorSpace(0))

    def __isub__(self, other):
        assert self.dim == other.dim
        if self._refcount[0] > 1:
            self._deep_copy()
        other_dtype = other.base._array.dtype if other.is_view else other._array.dtype
        common_dtype = np.promote_types(self._array.dtype, other_dtype)
        if self._array.dtype != common_dtype:
            self._array = self._array.astype(common_dtype)
>       self._array[:self._len] -= other.base._array[other.ind] if other.is_view else other._array[:other._len]
E       ValueError: operands could not be broadcast together with shapes (2,0) (4,0) (2,0)

src/pymor/vectorarrays/numpy.py:313: ValueError
-------------------------------------------------------------------------------- Hypothesis ---------------------------------------------------------------------------------
Falsifying example: test_iter(
    vector_array=NumpyVectorArray([], NumpyVectorSpace(0)),
)
============================================================================= warnings summary ==============================================================================
/usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py:1148
  /usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py:1148: PytestConfigWarning: Unknown config ini key: pep8ignore
  
    self._warn_or_fail_if_strict("Unknown config ini key: {}\n".format(key))

/usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py:1148
  /usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py:1148: PytestConfigWarning: Unknown config ini key: pep8maxlinelength
  
    self._warn_or_fail_if_strict("Unknown config ini key: {}\n".format(key))

-- Docs: https://docs.pytest.org/en/stable/warnings.html
======================================================================= memory consumption estimates ========================================================================
pymortests::vectorarray.py::test_iter  - 248.0 KB
========================================================================== short test summary info ==========================================================================
FAILED src/pymortests/vectorarray.py::test_iter - ValueError: operands could not be broadcast together with shapes (2,0) (4,0) (2,0)
=============================================================== 1 failed, 57 deselected, 2 warnings in 5.78s ================================================================

[sdrave]

I can replicate that as is. Maybe it's a bug in your (older) hypothesis version.

Possibly. It was the same version CI used. With a newer version, reproduce_failure works. Still, without the decorator, --pdb stops at the wrong location.

[renefritze]

I can replicate that as is. Maybe it's a bug in your (older) hypothesis version.

Possibly. It was the same version CI used.

I don't think so? This uses 5.28.0, you used 5.19.0.

[sdrave]

I can replicate that as is. Maybe it's a bug in your (older) hypothesis version.

Possibly. It was the same version CI used.

I don't think so? This uses 5.28.0, you used 5.19.0.

Probably got it from here.

[sdrave]

@pmli, can this be merged?