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[Lapack] Please could you help me?

Salim,

Extract from http://www.netlib.org/lapack/double/dgeev.f
      SUBROUTINE DGEEV( JOBVL, JOBVR, N, A, LDA, WR, WI, VL, LDVL, VR,
     $                  LDVR, WORK, LWORK, INFO )

*  LWORK   (input) INTEGER
*          The dimension of the array WORK.  LWORK >= max(1,3*N), and
*          if JOBVL = 'V' or JOBVR = 'V', LWORK >= 4*N.  For good
*          performance, LWORK must generally be larger.
*
*          If LWORK = -1, then a workspace query is assumed; the  
routine
*          only calculates the optimal size of the WORK array, returns
*          this value as the first entry of the WORK array, and no  
error
*          message related to LWORK is issued by XERBLA.


The first call is to get the workspace (LWORK = -1, here c_m1=-1)
This first call does not do any computations, it just return the  
worksapce size neede

Then you allocate the space (your workspace is w)

Then you do the second call with the appropriate workspace and  
workspace size.
This second call will do the computations needed.

hope it helps
Julie
On Jun 1, 2008, at 9:18 AM, salim.harouat@Domain.Removed wrote:

Hello,

I have got a question.
Please could you tell me why in the joined file, we need to call the  
function dgeev_() twice?

Thank you very much in advance
Salim



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Julie Langou; Research Associate in Computer Science
Innovative Computing Laboratory;
University of Tennessee from Denver, Colorado ;-)
julie@Domain.Removed; http://www.cs.utk.edu/~julie/







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