On Wed, Jul 31, 2013 at 1:09 PM, Marc de Klerk <deklerkmc@gmail.com> wrote:

Hi guys,

I've been using np.ravel(). This morning I tried to lookup the difference between np.ravel() and np.ascontiguousarray(). Does anybody know?

I am not sure if this helps as I don't know your purpose for using np.ravel / np.ascontiguousarray. I got to know about the ndarray.flags method yesterday from Stefan while discussion on this PR.

In [15]: a = np.arange(20).reshape((4,5))

In [16]: a

Out[16]:

array([[ 0, 1, 2, 3, 4],

[ 5, 6, 7, 8, 9],

[10, 11, 12, 13, 14],

[15, 16, 17, 18, 19]])

In [17]: a.flags

Out[17]:

C_CONTIGUOUS : True

F_CONTIGUOUS : False

OWNDATA : False

WRITEABLE : True

ALIGNED : True

UPDATEIFCOPY : False

In [18]: b = np.ravel(a)

In [20]: b

Out[20]:

array([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,

17, 18, 19])

In [21]: b.flags

Out[21]:

C_CONTIGUOUS : True

F_CONTIGUOUS : True

OWNDATA : False

WRITEABLE : True

ALIGNED : True

UPDATEIFCOPY : False

Hope this helps!!

Marc

On Sunday, July 21, 2013 6:37:47 AM UTC+2, Chintak Sheth wrote:
Hi Ronnie,

On Jul 21, 2013 10:00 AM, "Ronnie Ghose" <ronnie...@gmail.com> wrote:
>
> So in skimage/colors why does it matter if the array is contiguous? Is this for Cython operations later?
>

Yeah it is mainly for using memory views in Cython which is initialized as C contiguous.
`cdef some_type[:. ::1] var_name`

In thus case ::1 is for C contiguous.

Chintak

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