problem of workspace size in DGESSD

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problem of workspace size in DGESSD

Postby lapreste » Thu Jan 05, 2006 6:18 am

I have read a message cocerning DGER errors after DGESV
I have a similar problem when I want use DGESDD with jobz 'N' to compute only the singular values.

To do that I issue a call with LWORK = -1 to obtain the correct size of the WORK parameter.

The returned needed size is 1, So I create an array of the requested size and I issue a new call to DGESSD and get an error message from DGEBRD :

** On entry to DGEBRD parameter number 10 had an illegal value

parameter 10 is the size of the workspace required by DGEBRD internally i.e. WORK.

If I issue the second call to DGEBRD with a differnt correct size for WORK for example 64*(N+M), which is quite optimal for DGEBRD on my system,
everything works fine...

It is of course always possible that I have mistaken some way, but I think it can be a bug.

It seems to me that the returned size is incorrectly computed to 1 in the 'N' case not taking account of the internal needs of DGEBRD.

In the 'A' case everything looks to go well.

thanks for answers or hints
lapreste
 
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Postby Julien Langou » Thu Jan 05, 2006 10:35 am

Did you apply the modification from 10/5/2000 available at:
http://www.netlib.org/lapack/release_notes.html
?

If no, can you apply the patch. Note that you can get all the modified file in one single tar file at:
http://www.netlib.org/lapack-dev/lapack--3.0--patch--10042002.tgz

If your version is the updated one, can you give the exact calling sequence, i.e. what are JOBZ, M, N ?

Julien
Julien Langou
 
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Postby lapreste » Thu Jan 05, 2006 11:14 am

thank you,

I have not used the patches yet , in fact I work under a debian ubuntu breezy, and I wonder why there is no library update for bugs lasting from so long times ?

All the way, thanks a lot and I will try to apply all patches.
lapreste
 
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Joined: Thu Jan 05, 2006 5:44 am


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