DPPFA(3F)

NAME
     DPPFA   - DPPFA factors a double precision symmetric positive definite
     matrix stored in packed form.

     DPPFA is usually called by DPPCO, but it can be called directly with a
     saving in time if  RCOND  is not needed.  (time for DPPCO) = (1 +
     18/N)*(time for DPPFA) .


SYNOPSYS
      SUBROUTINE DPPFA(AP,N,INFO)

DESCRIPTION
     On Entry

     AP DOUBLE PRECISION (N*(N+1)/2)
        the packed form of a symmetric matrix  A .  The
        columns of the upper triangle are stored sequentially
        in a one-dimensional array of length  N*(N+1)/2 .
        See comments below for details.

     N INTEGER
        the order of the matrix  A .  On Return

     AP an upper triangular matrix  R , stored in packed
        form, so that  A = TRANS(R)*R .

     INFO INTEGER
        = 0  for normal return.
        = K  if the leading minor of order  K  is not
        positive definite.  Packed Storage The following program segment will
     pack the upper triangle of a symmetric matrix.
        K = 0
        DO 20 J = 1, N
        DO 10 I = 1, J
        K = K + 1
        AP(K) = A(I,J)
        10    CONTINUE
        20 CONTINUE LINPACK.  This version dated 08/14/78 .  Cleve Moler,
     University of New Mexico, Argonne National Lab.  Subroutines and
     Functions BLAS DDOT Fortran DSQRT