The NumPy Fortran-ordering quiz
oliphant.travis at ieee.org
Wed Oct 18 13:31:18 CDT 2006
> I'm not talking about the keyword in the ravel call, I'm talking about
> the flag in a.
Ah. Yes, I see. I misunderstood. Of course ravel ignores the FORTRAN
flag (actually it doesn't because if a copy is not necessary it doesn't
make one). The key is that the Python user doesn't need to care about
the array flag unless they are interfacing to compiled code. That's the
point of the flag. It's actually redundant because it could be checked
every time it's needed. But, right now, it's kept updated so that the
check is simple. The same is true with the C-CONTIGUOUS flag (called
> The question is: do we *need* a fortran flag.
No, you don't *need* the flag. But, it saves copying data to check it
(look how many times ISFORTRAN is called in the code). Without the flag
all of those cases would need to do a strides-check which is done in the
> I am argueing not, because the only need is for fortran contiguous
> arrays to pass to fortran function, or translation from fortran
> contiguous arrays to numpy arrays. What I am saying is that things are
> unnecessarily complicated.
I disagree. It's actually not that complicated. Even if it was
compilcated to implement, the point is that it is now done. There is no
sense ripping it out (that would be a huge pain and for what purpose?)
The FORTRAN flag gives us a lot more flexibility when it comes to
copying data or not.
I think part of the complication is that you are misunderstanding some
of the terms and the purposes of the keywords.
> None of the LaPack stuff seems to use the Fortran stuff, they just
> transpose and copy.
It doesn't now only because I haven't had time to go through and change
it, but it should. Look at scipy's LaPack interface. It (through
f2py) uses the FORTRAN stuff extensively (much was borrowed from there
in the first place).
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