[Scipy-tickets] [SciPy] #1717: QZ segfault on Windows for 0.11.0rc1

SciPy Trac scipy-tickets@scipy....
Wed Aug 8 16:01:33 CDT 2012


#1717: QZ segfault on Windows for 0.11.0rc1
--------------------------+-------------------------------------------------
 Reporter:  rgommers      |       Owner:  somebody
     Type:  defect        |      Status:  new     
 Priority:  highest       |   Milestone:  0.11.0  
Component:  scipy.linalg  |     Version:  devel   
 Keywords:                |  
--------------------------+-------------------------------------------------

Comment(by jseabold):

 What do you mean that it doesn't look OK? The intention here is to return
 true if the eigenvalue is real, ie., the imaginary part is zero.

 The sort function expects three double precision arguments (alpha real
 part, alpha imaginary part, beta) and returns a logical array.

 From the dgges documentation:

 *  SELCTG  (external procedure) LOGICAL FUNCTION of three DOUBLE PRECISION
 arguments
 *          SELCTG must be declared EXTERNAL in the calling subroutine.
 *          If SORT = 'N', SELCTG is not referenced.
 *          If SORT = 'S', SELCTG is used to select eigenvalues to sort
 *          to the top left of the Schur form.
 *          An eigenvalue (ALPHAR(j)+ALPHAI(j))/BETA(j) is selected if
 *          SELCTG(ALPHAR(j),ALPHAI(j),BETA(j)) is true; i.e. if either
 *          one of a complex conjugate pair of eigenvalues is selected,
 *          then both complex eigenvalues are selected.
 *
 *          Note that in the ill-conditioned case, a selected complex
 *          eigenvalue may no longer satisfy SELCTG(ALPHAR(j),ALPHAI(j),
 *          BETA(j)) = .TRUE. after ordering. INFO is to be set to N+2
 *          in this case.

-- 
Ticket URL: <http://projects.scipy.org/scipy/ticket/1717#comment:15>
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