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From: mecej4 on 4 Aug 2010 17:37
kamaraju wrote:

>>
>> Do you mind divulging the error that you found in C.L.F. ? Thanks.
>
> No, not at all. Consider the sample code
>
> ! The problem is with the la_dgesdd.f90 routine assigning wrong value
> ! to JOBZ variable around line 202. It assigns JOBZ='A' where as in
> this case, it should have assigned JOBZ='S'.
> If you need any other information, please let me know.
>
>
> BTW, how do you attach files when posting via google groups?
>
> thanks
> raju

Thanks for reporting the details of the error here. I can confirm that the
error occurs with other compilers, and with Intel's MKL library, which is
adapted from Lapack/Lapack95.

The seg-fault occurs with some input. With other input, with MKL, I get the
error

MKL ERROR: Parameter 10 was incorrect on entry to DGESDD
Program terminated in LAPACK95 subroutine LA_GESDD
Error indicator, INFO = -10

The fix that you have suggested is appropriate only when either the matrix U
or VT (or both) in the S.V. decomposition

A = U . S . VT

is not passed full-size. There are four combinations of U and VT being
full-size or truncated to the useful part. Only when U and VT are both
full-size should JOBZ equal 'A'. If either has been passed truncated, JOBZ
= 'S' is appropriate. (I could be wrong here, this needs more checking).

This is definitely an bug that should be reported to the Lapack95
maintainers. Intel (MKL) and AMD (ACML) may also be contacted.

-- mecej4
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