SUBROUTINE DPPCO(AP,N,RCOND,Z,INFO)
C***BEGIN PROLOGUE  DPPCO
C***DATE WRITTEN   780814   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  D2B1B
C***KEYWORDS  CONDITION,DOUBLE PRECISION,FACTOR,LINEAR ALGEBRA,LINPACK,
C             MATRIX,PACKED,POSITIVE DEFINITE
C***AUTHOR  MOLER, C. B., (U. OF NEW MEXICO)
C***PURPOSE  Factors a double precision SYMMETRIC POSITIVE DEFINITE
C            matrix stored in packed form and estimates the condition of
C            the matrix.
C***DESCRIPTION
C
C     DPPCO factors a double precision symmetric positive definite
C     matrix stored in packed form
C     and estimates the condition of the matrix.
C
C     If  RCOND  is not needed, DPPFA is slightly faster.
C     To solve  A*X = B , follow DPPCO by DPPSL.
C     To compute  INVERSE(A)*C , follow DPPCO by DPPSL.
C     To compute  DETERMINANT(A) , follow DPPCO by DPPDI.
C     To compute  INVERSE(A) , follow DPPCO by DPPDI.
C
C     On Entry
C
C        AP      DOUBLE PRECISION (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     On Return
C
C        AP      an upper triangular matrix  R , stored in packed
C                form, so that  A = TRANS(R)*R .
C                If  INFO .NE. 0 , the factorization is not complete.
C
C        RCOND   DOUBLE PRECISION
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.  If INFO .NE. 0 , RCOND is unchanged.
C
C        Z       DOUBLE PRECISION(N)
C                a work vector whose contents are usually unimportant.
C                If  A  is singular to working precision, then  Z  is
C                an approximate null vector in the sense that
C                NORM(A*Z) = RCOND*NORM(A)*NORM(Z) .
C                If  INFO .NE. 0 , Z  is unchanged.
C
C        INFO    INTEGER
C                = 0  for normal return.
C                = K  signals an error condition.  The leading minor
C                     of order  K  is not positive definite.
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 DPPFA
C     BLAS DAXPY,DDOT,DSCAL,DASUM
C     Fortran DABS,DMAX1,DREAL,DSIGN
C***REFERENCES  DONGARRA J.J., BUNCH J.R., MOLER C.B., STEWART G.W.,
C                 *LINPACK USERS  GUIDE*, SIAM, 1979.
C***ROUTINES CALLED  DASUM,DAXPY,DDOT,DPPFA,DSCAL
C***END PROLOGUE  DPPCO