SUBROUTINE SSPCO(AP,N,KPVT,RCOND,Z)
C***BEGIN PROLOGUE  SSPCO
C***DATE WRITTEN   780814   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  D2B1A
C***KEYWORDS  CONDITION,FACTOR,LINEAR ALGEBRA,LINPACK,MATRIX,PACKED,
C             SYMMETRIC
C***AUTHOR  MOLER, C. B., (U. OF NEW MEXICO)
C***PURPOSE  Factors a real SYMMETRIC matrix stored in packed form
C            by elimination with symmetric pivoting and estimates
C            the condition of the matrix
C***DESCRIPTION
C
C     SSPCO factors a real symmetric matrix stored in packed
C     form by elimination with symmetric pivoting and estimates
C     the condition of the matrix.
C
C     If  RCOND  is not needed, SSPFA is slightly faster.
C     To solve  A*X = B , follow SSPCO by SSPSL.
C     To compute  INVERSE(A)*C , follow SSPCO by SSPSL.
C     To compute  INVERSE(A) , follow SSPCO by SSPDI.
C     To compute  DETERMINANT(A) , follow SSPCO by SSPDI.
C     To compute  INERTIA(A), follow SSPCO by SSPDI.
C
C     On Entry
C
C        AP      REAL (N*(N+1)/2)
C                the packed form of a symmetric matrix  A .  The
C                columns of the upper triangle are stored sequentially
C                in a one-dimensional array of length  N*(N+1)/2 .
C                See comments below for details.
C
C        N       INTEGER
C                the order of the matrix  A .
C
C     Output
C
C        AP      a block diagonal matrix and the multipliers which
C                were used to obtain it stored in packed form.
C                The factorization can be written  A = U*D*TRANS(U)
C                where  U  is a product of permutation and unit
C                upper triangular matrices , TRANS(U) is the
C                transpose of  U , and  D  is block diagonal
C                with 1 by 1 and 2 by 2 blocks.
C
C        KPVT    INTEGER(N)
C                an integer vector of pivot indices.
C
C        RCOND   REAL
C                an estimate of the reciprocal condition of  A .
C                For the system  A*X = B , relative perturbations
C                in  A  and  B  of size  EPSILON  may cause
C                relative perturbations in  X  of size  EPSILON/RCOND .
C                If  RCOND  is so small that the logical expression
C                           1.0 + RCOND .EQ. 1.0
C                is true, then  A  may be singular to working
C                precision.  In particular,  RCOND  is zero  if
C                exact singularity is detected or the estimate
C                underflows.
C
C        Z       REAL(N)
C                a work vector whose contents are usually unimportant.
C                If  A  is close to a singular matrix, then  Z  is
C                an approximate null vector in the sense that
C                NORM(A*Z) = RCOND*NORM(A)*NORM(Z) .
C
C     Packed Storage
C
C          The following program segment will pack the upper
C          triangle of a symmetric matrix.
C
C                K = 0
C                DO 20 J = 1, N
C                   DO 10 I = 1, J
C                      K = K + 1
C                      AP(K) = A(I,J)
C             10    CONTINUE
C             20 CONTINUE
C
C     LINPACK.  This version dated 08/14/78 .
C     Cleve Moler, University of New Mexico, Argonne National Lab.
C
C     Subroutines and Functions
C
C     LINPACK SSPFA
C     BLAS SAXPY,SDOT,SSCAL,SASUM
C     Fortran ABS,AMAX1,IABS,SIGN
C***REFERENCES  DONGARRA J.J., BUNCH J.R., MOLER C.B., STEWART G.W.,
C                 *LINPACK USERS  GUIDE*, SIAM, 1979.
C***ROUTINES CALLED  SASUM,SAXPY,SDOT,SSCAL,SSPFA
C***END PROLOGUE  SSPCO