subroutine rsg(nm,n,a,b,w,matz,z,fv1,fv2,ierr) c integer n,nm,ierr,matz real a(nm,n),b(nm,n),w(n),z(nm,n),fv1(n),fv2(n) c c this subroutine calls the recommended sequence of c subroutines from the eigensystem subroutine package (eispack) c to find the eigenvalues and eigenvectors (if desired) c for the real symmetric generalized eigenproblem ax = (lambda)bx. c c on input c c nm must be set to the row dimension of the two-dimensional c array parameters as declared in the calling program c dimension statement. c c n is the order of the matrices a and b. c c a contains a real symmetric matrix. c c b contains a positive definite real symmetric matrix. c c matz is an integer variable set equal to zero if c only eigenvalues are desired. otherwise it is set to c any non-zero integer for both eigenvalues and eigenvectors. c c on output c c w contains the eigenvalues in ascending order. c c z contains the eigenvectors if matz is not zero. c c ierr is an integer output variable set equal to an error c completion code described in the documentation for tqlrat c and tql2. the normal completion code is zero. c c fv1 and fv2 are temporary storage arrays. c c questions and comments should be directed to burton s. garbow, c mathematics and computer science div, argonne national laboratory c c this version dated august 1983. c c ------------------------------------------------------------------ c if (n .le. nm) go to 10 ierr = 10 * n go to 50 c 10 call reduc(nm,n,a,b,fv2,ierr) if (ierr .ne. 0) go to 50 if (matz .ne. 0) go to 20 c .......... find eigenvalues only .......... call tred1(nm,n,a,w,fv1,fv2) call tqlrat(n,w,fv2,ierr) go to 50 c .......... find both eigenvalues and eigenvectors .......... 20 call tred2(nm,n,a,w,fv1,z) call tql2(nm,n,w,fv1,z,ierr) if (ierr .ne. 0) go to 50 call rebak(nm,n,b,fv2,n,z) 50 return end