SUBROUTINE TRED3(N,NV,A,D,E,E2)
C***BEGIN PROLOGUE  TRED3
C***DATE WRITTEN   760101   (YYMMDD)
C***REVISION DATE  830518   (YYMMDD)
C***CATEGORY NO.  D4C1B1
C***KEYWORDS  EIGENVALUES,EIGENVECTORS,EISPACK
C***AUTHOR  SMITH, B. T., ET AL.
C***PURPOSE  Reduce real symmetric matrix stored in packed form to
C            symmetric tridiagonal matrix using orthogonal
C            transformations.
C***DESCRIPTION
C
C     This subroutine is a translation of the ALGOL procedure TRED3,
C     NUM. MATH. 11, 181-195(1968) by Martin, Reinsch, and Wilkinson.
C     HANDBOOK FOR AUTO. COMP., VOL.II-LINEAR ALGEBRA, 212-226(1971).
C
C     This subroutine reduces a REAL SYMMETRIC matrix, stored as
C     a one-dimensional array, to a symmetric tridiagonal matrix
C     using orthogonal similarity transformations.
C
C     On Input
C
C        n is the order of the matrix.
C
C        NV must be set to the dimension of the array parameter A
C          as declared in the calling program dimension statement.
C
C        A contains the lower triangle of the real symmetric
C          input matrix, stored row-wise as a one-dimensional
C          array, in its first N*(N+1)/2 positions.
C
C     On Output
C
C        A contains information about the orthogonal
C          transformations used in the reduction.
C
C        D contains the diagonal elements of the tridiagonal matrix.
C
C        E contains the subdiagonal elements of the tridiagonal
C          matrix in its last N-1 positions.  E(1) is set to zero.
C
C        E2 contains the squares of the corresponding elements of E.
C          E2 may coincide with E if the squares are not needed.
C
C     Questions and comments should be directed to B. S. Garbow,
C     APPLIED MATHEMATICS DIVISION, ARGONNE NATIONAL LABORATORY
C     ------------------------------------------------------------------
C***REFERENCES  B. T. SMITH, J. M. BOYLE, J. J. DONGARRA, B. S. GARBOW,
C                 Y. IKEBE, V. C. KLEMA, C. B. MOLER, *MATRIX EIGEN-
C                 SYSTEM ROUTINES - EISPACK GUIDE*, SPRINGER-VERLAG,
C                 1976.
C***ROUTINES CALLED  (NONE)
C***END PROLOGUE  TRED3