On 2010-01-11 14:31 PM, CELEN Erman wrote:
(I also noticed that this behavior is same under standard NumPy 1.4
with standard Python 2.6 on Windows. If you call numpy.log10(0.0) you
will get an "-inf" and no exceptions will be raised. Which is not the
case with Python's standard math.log10(0.0) which will raise a
ValueError)
Correct. This is numpy's intended behavior. See numpy.seterr() to enable
exceptions if you want them.
Numpy.seterr() doesn't seem to be working in case of log10(0.0) (output with
all standard: Python2.6 with NumPy1.4 on Windows-32bit is below)
Python 2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)]
on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import numpy
>>> numpy.seterr()
{'over': 'ignore', 'divide': 'ignore', 'invalid': 'ignore', 'under':
'ignore'}
>>> numpy.int16(32000) * numpy.int16(3)
30464
>>> numpy.log10(0.0)
-inf
>>> numpy.seterr(all='raise')
{'over': 'ignore', 'divide': 'ignore', 'invalid': 'ignore', 'under':
'ignore'}
>>> numpy.int16(32000) * numpy.int16(3)
Traceback (most recent call last):
File "<stdin>", line 1, in<module>
FloatingPointError: overflow encountered in short_scalars
>>> numpy.log10(0.0)
-inf
>>> numpy.log10(-1.0)
nan
>>> numpy.seterr()
{'over': 'raise', 'divide': 'raise', 'invalid': 'raise', 'under': 'raise'}
>>>
That might be an issue with how numpy is detecting the floating point exception
on Windows. Please report it. It works fine on OS X:
In [1]: np.seterr(all='raise')
Out[1]: {'divide': 'print', 'invalid': 'print', 'over': 'print', 'under':
'ignore'}
In [2]: np.log10(0.0)
---------------------------------------------------------------------------
FloatingPointError Traceback (most recent call last)
/Users/rkern/<ipython console> in <module>()
FloatingPointError: divide by zero encountered in log10
In [3]: np.log10(-1.0)
---------------------------------------------------------------------------
FloatingPointError Traceback (most recent call last)
/Users/rkern/<ipython console> in <module>()
FloatingPointError: invalid value encountered in log10
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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