[nm,n,w,e,matz,z,ierr]=rst(nm,n,w,e,matz,z,ierr);

function [nm,n,w,e,matz,z,ierr]=rst(nm,n,w,e,matz,z,ierr);
%***BEGIN PROLOGUE  RST
%***PURPOSE  Compute the eigenvalues and, optionally, the eigenvectors
%            of a real symmetric tridiagonal matrix.
%***LIBRARY   SLATEC (EISPACK)
%***CATEGORY  D4A5
%***TYPE      SINGLE PRECISION (RST-S)
%***KEYWORDS  EIGENVALUES, EIGENVECTORS, EISPACK
%***AUTHOR  Smith, B. T., et al.
%***DESCRIPTION
%
%     This subroutine calls the recommended sequence of
%     subroutines from the eigensystem subroutine package (EISPACK)
%     to find the eigenvalues and eigenvectors (if desired)
%     of a REAL SYMMETRIC TRIDIAGONAL matrix.
%
%     On Input
%
%        NM must be set to the row dimension of the two-dimensional
%          array parameter, Z, as declared in the calling program
%          dimension statement.  NM is an INTEGER variable.
%
%        N is the order of the matrix.  N is an INTEGER variable.
%          N must be less than or equal to NM.
%
%        W contains the diagonal elements of the real symmetric
%          tridiagonal matrix.  W is a one-dimensional REAL array,
%          dimensioned W(N).
%
%        E contains the subdiagonal elements of the matrix in its last
%          N-1 positions.  E(1) is arbitrary.  E is a one-dimensional
%          REAL array, dimensioned E(N).
%
%        MATZ is an INTEGER variable set equal to zero if only
%          eigenvalues are desired.  Otherwise, it is set to any
%          non-zero integer for both eigenvalues and eigenvectors.
%
%     On Output
%
%        W contains the eigenvalues in ascending order.
%
%        Z contains the eigenvectors if MATZ is not zero.  The eigen-
%          vectors are orthonormal.  Z is a two-dimensional REAL array,
%          dimensioned Z(NM,N).
%
%        IERR is an INTEGER flag set to
%          Zero       for normal return,
%          10*N       if N is greater than NM,
%          J          if the J-th eigenvalue has not been
%                     determined after 30 iterations.
%                     The eigenvalues and eigenvectors in the W and Z
%                     arrays should be correct for indices
%                     1, 2, ..., IERR-1.
%
%     Questions and comments should be directed to B. S. Garbow,
%     APPLIED MATHEMATICS DIVISION, ARGONNE NATIONAL LABORATORY
%     ------------------------------------------------------------------
%
%***REFERENCES  B. T. Smith, J. M. Boyle, J. J. Dongarra, B. S. Garbow,
%                 Y. Ikebe, V. C. Klema and C. B. Moler, Matrix Eigen-
%                 system Routines - EISPACK Guide, Springer-Verlag,
%                 1976.
%***ROUTINES CALLED  IMTQL1, IMTQL2
%***REVISION HISTORY  (YYMMDD)
%   760101  DATE WRITTEN
%   890831  Modified array declarations.  (WRB)
%   890831  REVISION DATE from Version 3.2
%   891214  Prologue converted to Version 4.0 format.  (BAB)
%   920501  Reformatted the REFERENCES section.  (WRB)
%***end PROLOGUE  RST
%
persistent i j ; 

if isempty(i), i=0; end;
if isempty(j), j=0; end;
w_shape=size(w);w=reshape(w,1,[]);
e_shape=size(e);e=reshape(e,1,[]);
z_shape=size(z);z=reshape([z(:).',zeros(1,ceil(numel(z)./prod([nm])).*prod([nm])-numel(z))],nm,[]);
%
%***FIRST EXECUTABLE STATEMENT  RST
if( n>nm )
ierr = fix(10.*n);
%
elseif( matz~=0 ) ;
%     .......... FIND BOTH EIGENVALUES AND EIGENVECTORS ..........
for i = 1 : n;
%
for j = 1 : n;
z(j,i) = 0.0e0;
end; j = fix(n+1);
%
z(i,i) = 1.0e0;
end; i = fix(n+1);
%
[nm,n,w,e,z,ierr]=imtql2(nm,n,w,e,z,ierr);
else;
%     .......... FIND EIGENVALUES ONLY ..........
[n,w,e,ierr]=imtql1(n,w,e,ierr);
end;
w_shape=zeros(w_shape);w_shape(:)=w(1:numel(w_shape));w=w_shape;
e_shape=zeros(e_shape);e_shape(:)=e(1:numel(e_shape));e=e_shape;
z_shape=zeros(z_shape);z_shape(:)=z(1:numel(z_shape));z=z_shape;
end
%DECK RT