[nm,n,a,w,matz,z,fv1,ierr]=rt(nm,n,a,w,matz,z,fv1,ierr);

function [nm,n,a,w,matz,z,fv1,ierr]=rt(nm,n,a,w,matz,z,fv1,ierr);
%***BEGIN PROLOGUE  RT
%***PURPOSE  Compute the eigenvalues and eigenvectors of a special real
%            tridiagonal matrix.
%***LIBRARY   SLATEC (EISPACK)
%***CATEGORY  D4A5
%***TYPE      SINGLE PRECISION (RT-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 special REAL
%     TRIDIAGONAL matrix.  The property of the matrix required for use
%     of this subroutine is that the products of pairs of corresponding
%     off-diagonal elements be all non-negative.  If eigenvectors are
%     desired, no product can be zero unless both factors are zero.
%
%     On Input
%
%        NM must be set to the row dimension of the two-dimensional
%          array parameter, A and Z, as declared in the calling
%          program dimension statement.  NM is an INTEGER variable.
%
%        N is the order of the matrix A.  N is an INTEGER variable.
%          N must be less than or equal to NM.
%
%        A contains the special real tridiagonal matrix in its first
%          three columns.  The subdiagonal elements are stored in the
%          last N-1 positions of the first column, the diagonal elements
%          in the second column, and the superdiagonal elements in the
%          first N-1 positions of the third column.  Elements A(1,1) and
%          A(N,3) are arbitrary.  A is a two-dimensional REAL array,
%          dimensioned A(NM,3).
%
%        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.  W is a
%          one-dimensional REAL array, dimensioned W(N).
%
%        Z contains the eigenvectors if MATZ is not zero.  The eigen-
%          vectors are not normalized.  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,
%          N+J        if A(J,1)*A(J-1,3) is negative,
%          2*N+J      if the product is zero with one factor non-zero,
%                     and MATZ is non-zero;
%          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.
%
%        FV1 is a one-dimensional REAL array used for temporary storage,
%          dimensioned FV1(N).
%
%     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  FIGI, FIGI2, 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  RT
%

a_orig=a;a_shape=[nm,3];a=reshape([a_orig(1:min(prod(a_shape),numel(a_orig))),zeros(1,max(0,prod(a_shape)-numel(a_orig)))],a_shape);
w_shape=size(w);w=reshape(w,1,[]);
z_shape=size(z);z=reshape([z(:).',zeros(1,ceil(numel(z)./prod([nm])).*prod([nm])-numel(z))],nm,[]);
fv1_shape=size(fv1);fv1=reshape(fv1,1,[]);
%
%***FIRST EXECUTABLE STATEMENT  RT
if( n>nm )
ierr = fix(10.*n);
%
elseif( matz~=0 ) ;
%     .......... FIND BOTH EIGENVALUES AND EIGENVECTORS ..........
[nm,n,a,w,fv1,z,ierr]=figi2(nm,n,a,w,fv1,z,ierr);
if( ierr==0 )
[nm,n,w,fv1,z,ierr]=imtql2(nm,n,w,fv1,z,ierr);
end;
else;
%     .......... FIND EIGENVALUES ONLY ..........
fv1_orig=fv1;    [nm,n,a,w,fv1,dumvar6,ierr]=figi(nm,n,a,w,fv1,fv1,ierr);    fv1(dumvar6~=fv1_orig)=dumvar6(dumvar6~=fv1_orig);
if( ierr<=0 )
[n,w,fv1,ierr]=imtql1(n,w,fv1,ierr);
end;
end;
a_orig(1:prod(a_shape))=a;a=a_orig;
w_shape=zeros(w_shape);w_shape(:)=w(1:numel(w_shape));w=w_shape;
z_shape=zeros(z_shape);z_shape(:)=z(1:numel(z_shape));z=z_shape;
fv1_shape=zeros(fv1_shape);fv1_shape(:)=fv1(1:numel(fv1_shape));fv1=fv1_shape;
end
%DECK RUNIF