[Scipy-tickets] [SciPy] #1645: incorrect lwork assertion in f2py wrapper for LAPACK xGERQF

SciPy Trac scipy-tickets@scipy....
Thu Apr 19 14:52:55 CDT 2012

#1645: incorrect lwork assertion in f2py wrapper for LAPACK xGERQF
 Reporter:  mike.wimmer   |       Owner:  somebody   
     Type:  defect        |      Status:  new        
 Priority:  normal        |   Milestone:  Unscheduled
Component:  scipy.linalg  |     Version:  devel      
 Keywords:                |  
 I noticed that the f2py wrapper for xGERQF has a wrong assertion with
 respect to the workspace size: In lines 575-580 of flapack.pyf.src (that's
 the name in the current development version, in 0.10.1 where I found the
 mistake, it's generic_flapack.pyf.src) we see

      integer intent(hide),depend(a):: m = shape(a,0)
      integer intent(hide),depend(a):: n = shape(a,1)
      <ftype> dimension(m,n),intent(in,out,copy,out=qr,aligned8) :: a
      <ftype> dimension(MIN(m,n)),intent(out) :: tau

      integer optional,intent(in),depend(n),check(lwork>=n||lwork==-1) ::

 i.e. a requirement that lwork > number of columns of the array. From the
 LAPACK documentation however (i.e.
 http://www.netlib.org/lapack/double/dgerqf.f ) we find

 *  LWORK   (input) INTEGER
 *          The dimension of the array WORK.  LWORK >= max(1,M).
 with M the number of rows.

 Hence, line 580 of flapack.pyf.src should read instead

      integer optional,intent(in),depend(m),check(lwork>=m||lwork==-1) ::

 I discovered this problem while linking scipy to MKL, where some of the RQ
 tests failed because of this issue.

Ticket URL: <http://projects.scipy.org/scipy/ticket/1645>
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