[Numpy-discussion] numpy log2 has bug

2011-03-23 Thread Dmitrey 
  from numpy import log2, __version__
   
   log2(2**63)  

   Traceback (most recent call
   last):   

   File stdin, line 1, in
   module 
   
   AttributeError: log2
__version__
   '2.0.0.dev-1fe8136'
   (doesn't work with 1.3.0 as well)
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Re: [Numpy-discussion] numpy log2 has bug

2011-03-23 Thread josef . pktd 
2011/3/23 Dmitrey tm...@ukr.net:
 from numpy import log2, __version__

 log2(2**63)
 Traceback (most recent call
 last):
   File stdin, line 1, in
 module
 AttributeError: log2
 __version__
 '2.0.0.dev-1fe8136'
 (doesn't work with 1.3.0 as well)

 np.array([2**63])
array([9223372036854775808], dtype=object)

 log2(2.**63)
62.993
 log2(2**63)
Traceback (most recent call last):
  File pyshell#9, line 1, in module
log2(2**63)
AttributeError: log2

integer conversion problem

Josef




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Re: [Numpy-discussion] numpy log2 has bug

2011-03-23 Thread Robert Kern 
On Wed, Mar 23, 2011 at 13:51,  josef.p...@gmail.com wrote:
 2011/3/23 Dmitrey tm...@ukr.net:
 from numpy import log2, __version__

 log2(2**63)
 Traceback (most recent call
 last):
   File stdin, line 1, in
 module
 AttributeError: log2
 __version__
 '2.0.0.dev-1fe8136'
 (doesn't work with 1.3.0 as well)

 np.array([2**63])
 array([9223372036854775808], dtype=object)

 log2(2.**63)
 62.993
 log2(2**63)
 Traceback (most recent call last):
  File pyshell#9, line 1, in module
    log2(2**63)
 AttributeError: log2

 integer conversion problem

Right. numpy cannot safely convert a long object of that size to a
dtype it knows about, so it leaves it as an object array. Most ufuncs
operate on object arrays by looking for a method on each element with
the name of the ufunc. So

  np.log2(np.array([x], dtype=object))

will look for x.log2().

-- 
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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