SBGVX computes a few eigenvalues/eigenvectors of a real symmetric matrix so it should be very useful for FEA where we want only a few eigenvalues/vectors of a very large matrix. So, I implemented a test example following the documentations but I cannot get it to work. I get an access violation.

Does anyone has a working example using this routine?

Here is mine:

program Console1 implicit none ! Variables ! http://software.intel.com/sites/products/documentation/hpc/mkl/mklman/index.htm#GUID-659297EE-D35B-428C-ABBE-1A7EBE2B0F6E.htm#GUID-659297EE-D35B-428C-ABBE-1A7EBE2B0F6E ! ! N: matrix size ! NJ: number of upper diagonals + 1 integer, parameter :: N=3, NJ=2, ku=NJ-1, kl=0, ldab=ku+1, iwork=7*N !compute eigenvalues with index il to iu included integer, parameter :: il=1, iu=2, ldz=N, ldq=N integer info, m integer, dimension (N) :: ifail doubleprecision, dimension (N,N) :: KG, KM doubleprecision, dimension (ldab,N) :: KGB, KMB doubleprecision, dimension (N) :: W !eigenvalues doubleprecision, dimension (N,N) :: q, z doubleprecision vl, vu !not referenced if range="I" doubleprecision, parameter :: abstol=0.0D-3 !absolute error tolerance for eigenvalues doubleprecision, dimension (iwork) :: work character*1, parameter :: jobz="V" !compute eigenvalues character*1, parameter :: range="I" !compute in interval il--iu character*1, parameter :: uplo="U" !upper triangular symmetric !local integer i,j m = iu-il+1 !test matrix KG = 0 KM = 0 KG(1,1) = 100 KG(2,2) = 100 KG(1,2) = 25 KG(2,1) = 25 do i=1,N KM(i,i) = 1 enddo print *, "KG" write(*,"(3G9.3)") ((KG(i,j),j=1,N),i=1,N) !copy to band form using !http://software.intel.com/sites/products/documentation/hpc/mkl/mklman/index.htm#GUID-659297EE-D35B-428C-ABBE-1A7EBE2B0F6E.htm#GUID-659297EE-D35B-428C-ABBE-1A7EBE2B0F6E KGB = 0 KMB = 0 do i=1,N do j=1,N if (i.ge.max(1,j-ku).and.i.le.min(N,j+kl)) KGB(ku+1+i-j,j) = KG(i,j) if (i.ge.max(1,j-ku).and.i.le.min(N,j+kl)) KMB(ku+1+i-j,j) = KM(i,j) enddo enddo print *, "KGB" write(*,"(3G9.3)") ((KGB(i,j),j=1,N),i=1,ku+1) print *, "KGM" write(*,"(3G9.3)") ((KMB(i,j),j=1,N),i=1,ku+1) !call sbgvx(KGB, KMB, w) ! 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 call dsbgvx(jobz, range, uplo, N, ku, ku, KGB, ldab, KMB, ldab, q, ldq, vl, vu, il, iu, abstol, m, w, z, ldz, work, iwork, ifail, info) print *, "Eigenvalues found=",m print *, "Eigenvalues. Info=",info write(*,*) W pause "Hit ENTER to continue" end program Console1