dpofa.f
SUBROUTINE DPOFA (A, LDA, N, INFO)
C***BEGIN PROLOGUE DPOFA
C***PURPOSE Factor a real symmetric positive definite matrix.
C***LIBRARY SLATEC (LINPACK)
C***CATEGORY D2B1B
C***TYPE DOUBLE PRECISION (SPOFA-S, DPOFA-D, CPOFA-C)
C***KEYWORDS LINEAR ALGEBRA, LINPACK, MATRIX FACTORIZATION,
C POSITIVE DEFINITE
C***AUTHOR Moler, C. B., (U. of New Mexico)
C***DESCRIPTION
C
C DPOFA factors a double precision symmetric positive definite
C matrix.
C
C DPOFA is usually called by DPOCO, but it can be called
C directly with a saving in time if RCOND is not needed.
C (time for DPOCO) = (1 + 18/N)*(time for DPOFA) .
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 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***REFERENCES J. J. Dongarra, J. R. Bunch, C. B. Moler, and G. W.
C Stewart, LINPACK Users' Guide, SIAM, 1979.
C***ROUTINES CALLED DDOT
C***REVISION HISTORY (YYMMDD)
C 780814 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890831 Modified array declarations. (WRB)
C 890831 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900326 Removed duplicate information from DESCRIPTION section.
C (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE DPOFA