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SUBROUTINE RT(NM,N,A,W,MATZ,Z,FV1,IERR)
C
INTEGER N,NM,IERR,MATZ
REAL 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