[SciPy-Dev] Sporadic failures of tests of signal.correlate with dtype complex64

[Warren Weckesser]

On Mac OSX 10.5.8, I'm seeing occasional failures like the following:

$ python -c "import scipy.signal; scipy.signal.test()"
Running unit tests for scipy.signal
NumPy version 1.5.0.dev8716
NumPy is installed in
/Users/warren/tmp_py_install/lib/python2.6/site-packages/numpy
SciPy version 0.9.0.dev6856
SciPy is installed in
/Users/warren/tmp_py_install/lib/python2.6/site-packages/scipy
Python version 2.6.5 |EPD 6.2-2 (32-bit)| (r265:79063, May 28 2010,
15:13:03) [GCC 4.0.1 (Apple Inc. build 5488)]
nose version 0.11.3
................./Users/warren/tmp_py_install/lib/python2.6/site-packages/scipy/signal/filter_design.py:256:
BadCoefficients: Badly conditioned filter coefficients (numerator): the
results may be meaningless
  "results may be meaningless", BadCoefficients)
......................................................F...............................................................................................................................................................................................................................................
======================================================================
FAIL: test_rank1_same (test_signaltools.TestCorrelateComplex64)
----------------------------------------------------------------------
Traceback (most recent call last):
  File
"/Users/warren/tmp_py_install/lib/python2.6/site-packages/scipy/signal/tests/test_signaltools.py",
line 606, in test_rank1_same
    assert_array_almost_equal(y, y_r)
  File
"/Users/warren/tmp_py_install/lib/python2.6/site-packages/numpy/testing/utils.py",
line 774, in assert_array_almost_equal
    header='Arrays are not almost equal')
  File
"/Users/warren/tmp_py_install/lib/python2.6/site-packages/numpy/testing/utils.py",
line 618, in assert_array_compare
    raise AssertionError(msg)
AssertionError:
Arrays are not almost equal

(mismatch 10.0%)
 x: array([-6.76370811-8.55324841j,  0.68672836-4.2681613j ,
       -3.22760987-8.69287109j,  0.75051951-5.50820398j,
       -7.33016682-1.14685655j, -5.99573374+7.84123898j,...
 y: array([-6.76370859-8.55324745j,  0.68672895-4.2681613j ,
       -3.22761011-8.69286919j,  0.75051963-5.50820446j,
       -7.33016682-1.14685678j, -5.99573517+7.84123898j,...

----------------------------------------------------------------------
Ran 311 tests in 2.307s

FAILED (failures=1)

$ python -c "import scipy.signal; scipy.signal.test()"
Running unit tests for scipy.signal
NumPy version 1.5.0.dev8716
NumPy is installed in
/Users/warren/tmp_py_install/lib/python2.6/site-packages/numpy
SciPy version 0.9.0.dev6856
SciPy is installed in
/Users/warren/tmp_py_install/lib/python2.6/site-packages/scipy
Python version 2.6.5 |EPD 6.2-2 (32-bit)| (r265:79063, May 28 2010,
15:13:03) [GCC 4.0.1 (Apple Inc. build 5488)]
nose version 0.11.3
................./Users/warren/tmp_py_install/lib/python2.6/site-packages/scipy/signal/filter_design.py:256:
BadCoefficients: Badly conditioned filter coefficients (numerator): the
results may be meaningless
  "results may be meaningless", BadCoefficients)
.......................................................F..............................................................................................................................................................................................................................................
======================================================================
FAIL: test_rank1_same_old (test_signaltools.TestCorrelateComplex64)
----------------------------------------------------------------------
Traceback (most recent call last):
  File
"/Users/warren/tmp_py_install/lib/python2.6/site-packages/numpy/testing/decorators.py",
line 257, in _deprecated_imp
    f(*args, **kwargs)
  File
"/Users/warren/tmp_py_install/lib/python2.6/site-packages/scipy/signal/tests/test_signaltools.py",
line 641, in test_rank1_same_old
    assert_array_almost_equal(y, y_r)
  File
"/Users/warren/tmp_py_install/lib/python2.6/site-packages/numpy/testing/utils.py",
line 774, in assert_array_almost_equal
    header='Arrays are not almost equal')
  File
"/Users/warren/tmp_py_install/lib/python2.6/site-packages/numpy/testing/utils.py",
line 618, in assert_array_compare
    raise AssertionError(msg)
AssertionError:
Arrays are not almost equal

(mismatch 10.0%)
 x: array([ 2.46665049+2.02072477j, -7.42591763-0.54789257j,
        3.41454220-0.15863085j, -0.14030695+5.01129198j,
       -2.11230707+2.68583822j,  7.78784609+7.19434834j,...
 y: array([ 2.46665049+2.02072501j, -7.42591763-0.54789257j,
        3.41454196-0.15863061j, -0.14030659+5.01129246j,
       -2.11230707+2.68583822j,  7.78784752+7.19434786j,...

----------------------------------------------------------------------
Ran 311 tests in 2.623s

FAILED (failures=1)


The above tests are part of a suite of tests that use random data, and
usually the tests all pass.  It took several tries to get the above
failures.

I suspect the problem is simply that the default tolerance of
'assert_array_almost_equal' is too small for the complex64 data type for
these tests.

Could someone verify that they can reproduce those failures?  Does simply
increasing the tolerance of the test look like a reasonable fix?


Warren
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