SUBROUTINE DPOCO(A,LDA,N,RCOND,Z,INFO)
C***BEGIN PROLOGUE  DPOCO
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,POSITIVE DEFINITE
C***AUTHOR  MOLER, C. B., (U. OF NEW MEXICO)
C***PURPOSE  Factors a double precision SYMMETRIC POSITIVE DEFINITE
C            matrix and estimates the condition of the matrix.
C***DESCRIPTION
C
C     DPOCO factors a double precision symmetric positive definite
C     matrix and estimates the condition of the matrix.
C
C     If  RCOND  is not needed, DPOFA is slightly faster.
C     To solve  A*X = B , follow DPOCO by DPOSL.
C     To compute  INVERSE(A)*C , follow DPOCO by DPOSL.
C     To compute  DETERMINANT(A) , follow DPOCO by DPODI.
C     To compute  INVERSE(A) , follow DPOCO by DPODI.
C
C     On Entry
C
C        A       DOUBLE PRECISION(LDA, N)
C                the symmetric matrix to be factored.  Only the
C                diagonal and upper triangle are used.
C
C        LDA     INTEGER
C                the leading dimension of the array  A .
C
C        N       INTEGER
C                the order of the matrix  A .
C
C     On Return
C
C        A       an upper triangular matrix  R  so that  A = TRANS(R)*R
C                where  TRANS(R)  is the transpose.
C                The strict lower triangle is unaltered.
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 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                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     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 DPOFA
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,DPOFA,DSCAL
C***END PROLOGUE  DPOCO