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Workspace for DGESDD in LAPACK 3.4.2

PostPosted: Mon Oct 08, 2012 4:36 pm
by simon2212
The size of the workspace for DGESDD for JOBZ = 'S' or 'A' has been changed in LAPACK 3.4.2, and is set by LWORK. The current description of LWORK reads:

Code: Select all
LWORK >= 3*min(M,N) +
         max(max(M,N),4*min(M,N)*min(M,N)+3*min(M,N)+max(M,N)).


In the second line, both arguments of max contain max(M,N), and so the the function is redundant - the second argument will always be realised.
So the description could be simplified to:

Code: Select all
LWORK >= 3*min(M,N) +
         4*min(M,N)*min(M,N)+3*min(M,N)+max(M,N)


or further simplified to

Code: Select all
LWORK >= min(M,N)*(6+4*min(M,N))+max(M,N)

Re: Workspace for DGESDD in LAPACK 3.4.2

PostPosted: Mon Oct 08, 2012 5:13 pm
by admin
Indeed Simon,
Thank you this has been corrected in our repository.
Julie