[Numpy-discussion] improving arraysetops
neilcrighton at gmail.com
Wed Jun 17 06:11:47 EDT 2009
> > What about merging unique and unique1d? They're essentially identical for an
> > array input, but unique uses the builtin set() for non-array inputs and so is
> > around 2x faster in this case - see below. Is it worth accepting a speed
> > regression for unique to get rid of the function duplication? (Or can they be
> > combined?)
> unique1d can return the indices - can this be achieved by using set(), too?
No, set() can't return the indices as far as I know.
> The implementation for arrays is the same already, IMHO, so I would
> prefer adding return_index, return_inverse to unique (automatically
> converting input to array, if necessary), and deprecate unique1d.
> We can view it also as adding the set() approach to unique1d, when the
> return_index, return_inverse arguments are not set, and renaming
> unique1d -> unique.
This sounds good. If you don't have time to do it, I don't mind having
a go at writing
a patch to implement these changes (deprecate the existing unique1d, rename
unique1d to unique and add the set approach from the old unique, and the other
changes mentioned in http://projects.scipy.org/numpy/ticket/1133).
> I have found a strange bug in unique():
> In : l = list(np.random.randint(100, size=1000))
> In : %timeit np.unique(l)
> UnicodeEncodeError Traceback (most recent call last)
> /usr/lib64/python2.5/site-packages/IPython/iplib.py in ipmagic(self, arg_s)
> 951 else:
> 952 magic_args = self.var_expand(magic_args,1)
> --> 953 return fn(magic_args)
> 955 def ipalias(self,arg_s):
> /usr/lib64/python2.5/site-packages/IPython/Magic.py in
> magic_timeit(self, parameter_s)
> 1830 best
> * scaling[order],
> -> 1831
> 1832 if tc > tc_min:
> 1833 print "Compiler time: %.2f s" % tc
> UnicodeEncodeError: 'ascii' codec can't encode character u'\xb5' in
> position 28: ordinal not in range(128)
> It disappears after increasing the array size, or the integer size.
> In : np.__version__
> Out: '1.4.0.dev7047'
Weird! From the error message, it looks like a problem with ipython's timeit
function rather than unique. I can't reproduce it on my machine
(numpy 1.4.0.dev, r7059; IPython 0.10.bzr.r1163 ).
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