[SciPy-dev] problem with linalg.cholesky?

Andrew Jaffe a.h.jaffe at gmail.com
Fri Dec 2 15:56:39 CST 2005


Travis Oliphant wrote:
> Andrew Jaffe wrote:
> 
>>If there's no problem there, I guess the questions are: does 
>>_castCopyAndTranspose result in a non-contiguous array on all platforms? 
>>And does lapack_lite.dpotrf() balk at that, and why?
>> 
>>
> 
> No, it doesn't, that's what has me stumped.  It should be returning a 
> contiguous array (because of the .astype method).
> 
> So, figuring out why the .astype() method is not returning a contiguous 
> array is the key to understanding this, I think.
> 
> If you could determine what the parameters being passed to the .astype() 
> method are and try to reproduce the problem of not getting a contiguous 
> parameter on output, that would be very helpful.
> 
> Sorry for your trouble.
> 

OK, on my machine, the astype() method only gives a non-contiguous array 
when the old and new types are different:

In [33]: a = identity(4, Float64)

In [34]: print transpose(a).astype(Float64).flags
{'WRITEABLE': True, 'UPDATEIFCOPY': False, 'NOTSWAPPED': True, 
'CONTIGUOUS': False, 'FORTRAN': True, 'ALIGNED': True, 'OWNDATA': True}

In [35]: print transpose(a).astype(Float32).flags
{'WRITEABLE': True, 'UPDATEIFCOPY': False, 'NOTSWAPPED': True, 
'CONTIGUOUS': True, 'FORTRAN': False, 'ALIGNED': True, 'OWNDATA': True}

A




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