DPPFA(3F)DPPFA(3F)NAMEDPPFA - 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
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