Re: [Numpy-discussion] What does Fortran order mean?

[Stefan v. d. W. <st...@su...>]

On Mon, Oct 16, 2006 at 02:20:04PM -0600, Charles R Harris wrote:
> Travis,
>=20
> I note that
>=20
> >>> a =3D arange(6).reshape(2,3,order=3D'F')
> >>> a
> array([[0, 1, 2],
>        [3, 4, 5]])
>=20
> Shouldn't that be 3x2? Or maybe [[0,2,4],[1,3,5]]? Reshape is making a =
copy,
> but flat, flatten, and tostring all show the elements in 'C' order. I a=
sk
> because I wonder if changing the order can be used to prepare arrays fo=
r input
> into the LaPack routines.

I think that the calculation of 'a' above is correct, but that the
memory representation is incorrect.  For example (see attached script
-- which is overkill, I know), these commands:

x =3D N.arange(6,dtype=3Dfloat).reshape((2,3),order=3D'F')
catmem(x)

x =3D N.array([[0,1,2],[3,4,5]],order=3D'F',dtype=3Dfloat)
catmem(x)

x =3D N.array(N.arange(6,dtype=3Dfloat).reshape((2,3)),order=3D'F')
catmem(x)

x =3D N.asfortranarray(N.arange(6,dtype=3Dfloat).reshape((2,3)))
catmem(x)

yield the following results:

0.000000 1.000000 2.000000 3.000000 4.000000 5.000000=20
0.000000 3.000000 1.000000 4.000000 2.000000 5.000000=20
0.000000 3.000000 1.000000 4.000000 2.000000 5.000000=20
0.000000 3.000000 1.000000 4.000000 2.000000 5.000000=20

Regards
St=E9fan