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[Lapack] Problem with matrices bigger than 4GB

Dear Lapack Team,

I have a question concerning internal restrictions according to the  
size of the matrices.
I am using SSYEVX and my code works well with matrix dimensions up to  
30000x30000 using real*4 (less than 4GB memory).
I have tried to enlarge the dimension to 50000 or 70000. After approx.  
10 hours calculation after calling SSYEVX the only result is a  
segmentation fault. I expected the need of about 12 to 20 GB RAM. Are  
there any restrictions?

I am using a node of a compute cluster with 256 GB RAM, AMD Opteron  
processor and CentOS 64bit Linux system. Below you can see an extract  
of my program.

Thank you in advance. I am looking forward to read from you. I really  
could need some help.

Kind regards,


        integer*4 dim,lwork,liwork,nfdim

        PARAMETER (dim=71000)
        PARAMETER (lwork= 80000000)
        PARAMETER (liwork=80000000)
        PARAMETER (nfdim=71000)

        real*4 C(dim,dim),xx(dim,nfdim)
        real*4 work(lwork),lambda(dim)
        real*4 abstol,vl,vu

        integer*4 iwork(liwork),mm,il,iu,ifail(dim),ier

C      set up of matrix C ......, nmax <= dim

         call SSYEVX('V','I','U',nmax,c,dim,
      1   vl,vu,il,iu,abstol,mm,lambda,xx,dim,work,lwork,iwork,ifail,ier)

Sarah F. Wulf

CellNetworks-Cluster of Excellence (EXC81), BioQuant,
Heidelberg University
Im Neuenheimer Feld 267
69120 Heidelberg, Germany

Tel. +49-(0)6221-5451349
e-mail  sarah.wulf@Domain.Removed

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