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RT(NM,N,A,W,MATZ,Z,FV1,IERR)

       SUBROUTINE RT(NM,N,A,W,MATZ,Z,FV1,IERR)
 C
       INTEGER N,NM,IERR,MATZ
       DOUBLE PRECISION A(NM,3),W(N),Z(NM,N),FV1(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     OF A SPECIAL REAL TRIDIAGONAL MATRIX.
 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 MATRIX  A.
 C
 C        A  CONTAINS THE SPECIAL REAL TRIDIAGONAL MATRIX IN ITS
 C        FIRST THREE COLUMNS.  THE SUBDIAGONAL ELEMENTS ARE STORED
 C        IN THE LAST  N-1  POSITIONS OF THE FIRST COLUMN, THE
 C        DIAGONAL ELEMENTS IN THE SECOND COLUMN, AND THE SUPERDIAGONAL
 C        ELEMENTS IN THE FIRST  N-1  POSITIONS OF THE THIRD COLUMN.
 C        ELEMENTS  A(1,1)  AND  A(N,3)  ARE ARBITRARY.
 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 IMTQL1
 C           AND IMTQL2.  THE NORMAL COMPLETION CODE IS ZERO.
 C
 C        FV1  IS A TEMPORARY STORAGE ARRAY.
 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