SUBROUTINE DPPFA(AP,N,INFO)
C***BEGIN PROLOGUE  DPPFA
C***DATE WRITTEN   780814   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  D2B1B
C***KEYWORDS  DOUBLE PRECISION,FACTOR,LINEAR ALGEBRA,LINPACK,MATRIX,
C             PACKED,POSITIVE DEFINITE
C***AUTHOR  MOLER, C. B., (U. OF NEW MEXICO)
C***PURPOSE  Factors a d.p. SYMMETRIC POSITIVE DEFINITE matrix (packed
C            form)
C***DESCRIPTION
C
C     DPPFA factors a double precision symmetric positive definite
C     matrix stored in packed form.
C
C     DPPFA is usually called by DPPCO, but it can be called
C     directly with a saving in time if  RCOND  is not needed.
C     (time for DPPCO) = (1 + 18/N)*(time for DPPFA) .
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
C        INFO    INTEGER
C                = 0  for normal return.
C                = K  if the leading minor of order  K  is not
C                     positive definite.
C
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     BLAS DDOT
C     Fortran DSQRT
C***REFERENCES  DONGARRA J.J., BUNCH J.R., MOLER C.B., STEWART G.W.,
C                 *LINPACK USERS  GUIDE*, SIAM, 1979.
C***ROUTINES CALLED  DDOT
C***END PROLOGUE  DPPFA