SPPFA(3F)							     SPPFA(3F)

NAME    [Toc]    [Back]

     SPPFA   - SPPFA factors a real symmetric positive definite	matrix stored
     in	packed form.

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

SYNOPSYS    [Toc]    [Back]

      SUBROUTINE SPPFA(AP,N,INFO)

DESCRIPTION    [Toc]    [Back]

     On	Entry

     AP	REAL (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 SDOT Fortran SQRT


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