[SciPy-dev] lapack and blas

eric eric at scipy.org
Sat Jan 19 13:57:15 CST 2002


Hey Pearu,
 
> However, a bad news is that lapack and atlas lapack functions are not
> compatible. 

> For example,
> >>> LU,ipiv,X,info=flapack.c_sgesv([[1,2],[3,4]],[1,1])
> >>> print X
> [-0.5  0.5]

For some reason, this is solving using the transpose of the matrix. 

   1   3  x1 = 1  -->   x1 = -0.5
   2   4  x2   1        x2 =  0.5

Is this a problem with c_sgesv, or is f2py doing something incorrectly with the matrix transpose stuff?  I need to look at the magic your doing under the covers to handle all this, since I haven't figured out how you'd do it completely transparently in a way that never leads to ambiguity and also maintains efficiency.
Still, this is wrapping the C version of the function, so it should be the "trivial" case since nothing special needs to be done to the matrix.

> >>> LU,ipiv,X,info=flapack.f_sgesv([[1,2],[3,4]],[1,1])
> >>> print X
> [-0.99999994  0.99999994]

As you know, this is the correct answer.

eric
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