--- /dev/null
+*DECK RS
+ SUBROUTINE RS (NM, N, A, W, MATZ, Z, FV1, FV2, IERR)
+C***BEGIN PROLOGUE RS
+C***PURPOSE Compute the eigenvalues and, optionally, the eigenvectors
+C of a real symmetric matrix.
+C***LIBRARY SLATEC (EISPACK)
+C***CATEGORY D4A1
+C***TYPE SINGLE PRECISION (RS-S, CH-C)
+C***KEYWORDS EIGENVALUES, EIGENVECTORS, EISPACK
+C***AUTHOR Smith, B. T., et al.
+C***DESCRIPTION
+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 REAL SYMMETRIC matrix.
+C
+C On Input
+C
+C NM must be set to the row dimension of the two-dimensional
+C array parameters, A and Z, as declared in the calling
+C program dimension statement. NM is an INTEGER variable.
+C
+C N is the order of the matrix A. N is an INTEGER variable.
+C N must be less than or equal to NM.
+C
+C A contains the real symmetric matrix. A is a two-dimensional
+C REAL array, dimensioned A(NM,N).
+C
+C MATZ is an INTEGER variable set equal to zero if only
+C eigenvalues are desired. Otherwise, it is set to any
+C non-zero integer for both eigenvalues and eigenvectors.
+C
+C On Output
+C
+C A is unaltered.
+C
+C W contains the eigenvalues in ascending order. W is a one-
+C dimensional REAL array, dimensioned W(N).
+C
+C Z contains the eigenvectors if MATZ is not zero. The
+C eigenvectors are orthonormal. Z is a two-dimensional
+C REAL array, dimensioned Z(NM,N).
+C
+C IERR is an INTEGER flag set to
+C Zero for normal return,
+C 10*N if N is greater than NM,
+C J if the J-th eigenvalue has not been
+C determined after 30 iterations.
+C The eigenvalues, and eigenvectors if requested,
+C should be correct for indices 1, 2, ..., IERR-1.
+C
+C FV1 and FV2 are one-dimensional REAL arrays used for temporary
+C storage, dimensioned FV1(N) and FV2(N).
+C
+C Questions and comments should be directed to B. S. Garbow,
+C APPLIED MATHEMATICS DIVISION, ARGONNE NATIONAL LABORATORY
+C ------------------------------------------------------------------
+C
+C***REFERENCES B. T. Smith, J. M. Boyle, J. J. Dongarra, B. S. Garbow,
+C Y. Ikebe, V. C. Klema and C. B. Moler, Matrix Eigen-
+C system Routines - EISPACK Guide, Springer-Verlag,
+C 1976.
+C***ROUTINES CALLED TQL2, TQLRAT, TRED1, TRED2
+C***REVISION HISTORY (YYMMDD)
+C 760101 DATE WRITTEN
+C 890831 Modified array declarations. (WRB)
+C 890831 REVISION DATE from Version 3.2
+C 891214 Prologue converted to Version 4.0 format. (BAB)
+C 920501 Reformatted the REFERENCES section. (WRB)
+C***END PROLOGUE RS
+C
+ INTEGER N,NM,IERR,MATZ
+ REAL A(NM,*),W(*),Z(NM,*),FV1(*),FV2(*)
+C
+C***FIRST EXECUTABLE STATEMENT RS
+ IF (N .LE. NM) GO TO 10
+ IERR = 10 * N
+ GO TO 50
+C
+ 10 IF (MATZ .NE. 0) GO TO 20
+C .......... FIND EIGENVALUES ONLY ..........
+ CALL TRED1(NM,N,A,W,FV1,FV2)
+ CALL TQLRAT(N,W,FV2,IERR)
+ GO TO 50
+C .......... FIND BOTH EIGENVALUES AND EIGENVECTORS ..........
+ 20 CALL TRED2(NM,N,A,W,FV1,Z)
+ CALL TQL2(NM,N,W,FV1,Z,IERR)
+ 50 RETURN
+ END