[Numpy-discussion] Fortran binary files and numpy/scipy

Ryan May rmay31@gmail....
Mon Feb 2 14:07:35 CST 2009


Nils Wagner wrote:
>>> Is this a 64-bit problem ?
>>>
>> I don't know if it's a 64-bit problem per-se, so much as 
>> a disagreement between
>> fortran and numpy.  Numpy is making the size of the 
>> integer fields 8 bytes, while
>> in Fortran, they're only 4 bytes.  When constructing 
>> your dtype, use np.int32 or
>> '<i4' for your type for the integer fields, and see if 
>> that fixes it.
>>
> 
> dt = 
> np.dtype([('isize','int32'),('irow','int32'),('icol','int32'),('value','float')])
> 
> 
>>>> a
> array([(16, 0, 11, 1.2549267404367662e-321),
>         (1081065472, 16, 0, 7.9050503334599447e-323),
>         (12, 253, 0, 3.4485523805914514e-313),
>         (0, 16, 0, 5.3474293932967148e-312),
>         (0, 1079312384, 16, 3.3951932655444357e-313), (0, 
> 14, 251, 62.0),
>         (16, 0, 16, 3.1829936864479085e-313),
>         (250, 0, 1078525952, 7.9050503334599447e-323),
>         (16, 0, 16, 1.2302234581447039e-321),
>         (1078231040, 16, 0, 7.9050503334599447e-323),
>         (17, 248, 0, 3.4484552433329538e-313),
>         (0, 16, 0, 5.2413296037731544e-312),
>         (0, 1077805056, 16, 3.3951932655444357e-313), (0, 
> 19, 246, 27.0),
>         (16, 0, 16, 4.2439915819305446e-313),
>         (245, 0, 1077411840, 7.9050503334599447e-323)],
>        dtype=[('isize', '<i4'), ('irow', '<i4'), ('icol', 
> '<i4'), ('value', '<f8')])
> 

Maybe on 64-bit machines, the number of bytes is 64-bits instead of 32 (see the
fact that the first 12 bytes of the file are 16 0 11.  Try:

dt =
np.dtype([('isize','int64'),('irow','int32'),('icol','int32'),('value','float')])

Ryan

-- 
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma


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