[Numpy-discussion] hashing dtypes, new variation, old theme

Robert Kern robert.kern@gmail....
Wed Mar 16 11:21:53 CDT 2011


On Wed, Mar 16, 2011 at 10:27, Charles R Harris
<charlesr.harris@gmail.com> wrote:
>
> On Wed, Mar 16, 2011 at 8:56 AM, Charles R Harris
> <charlesr.harris@gmail.com> wrote:
>>
>>
>> On Wed, Mar 16, 2011 at 8:46 AM, Robert Kern <robert.kern@gmail.com>
>> wrote:
>>>
>>> On Wed, Mar 16, 2011 at 01:18, Matthew Brett <matthew.brett@gmail.com>
>>> wrote:
>>> > Hi,
>>> >
>>> > Running the test suite for one of our libraries, there seems to have
>>> > been a recent breakage of the behavior of dtype hashing.
>>> >
>>> > This script:
>>> >
>>> > import numpy as np
>>> >
>>> > data0 = np.arange(10)
>>> > data1 = data0 - 10
>>> >
>>> > dt0 = data0.dtype
>>> > dt1 = data1.dtype
>>> >
>>> > assert dt0 == dt1 # always passes
>>> > assert hash(dt0) == hash(dt1) # fails on latest
>>> >
>>> > fails on the current latest-ish - aada93306  and passes on a stock
>>> > 1.5.0.
>>> >
>>> > Is this expected?
>>>
>>> According to "git log hashdescr.c", nothing has changed in the
>>> implementation of the hash function since Oct 31, before numpy 1.5.1
>>> which also passes the second test. I'm not sure what would be causing
>>> the difference in HEAD.
>>>
>>
>> The 1.5.1 branch was based on 1.5.x, not master.
>>
>
> David's change isn't in 1.5.x, so apparently it wasn't backported.

Hmm. It works just before and just after that change, so the problem
is somewhere else.

-- 
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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