SPODI(3F)							     SPODI(3F)

NAME    [Toc]    [Back]

     SPODI   - SPODI computes the determinant and inverse of a certain real
     symmetric positive	definite matrix	(see below) using the factors computed
     by	SPOCO, SPOFA or	SQRDC.

SYNOPSYS    [Toc]    [Back]

      SUBROUTINE SPODI(A,LDA,N,DET,JOB)

DESCRIPTION    [Toc]    [Back]

     On	Entry

     A REAL(LDA, N)
	the output  A  from SPOCO or SPOFA
	or the output  X  from SQRDC.

     LDA INTEGER
	the leading dimension of the array  A .

     N INTEGER
	the order of the matrix	 A .

     JOB INTEGER
	= 11   both determinant	and inverse.
	= 01   inverse only.
	= 10   determinant only.  On Return

     A If SPOCO	or SPOFA was used to factor  A , then
	SPODI produces the upper half of INVERSE(A) .
	If SQRDC was used to decompose	X , then
	SPODI produces the upper half of INVERSE(TRANS(X)*X),
	where TRANS(X) is the transpose.
	Elements of  A	below the diagonal are unchanged.
	If the units digit of JOB is zero,  A  is unchanged.

     DET REAL(2)
	determinant of	A  or of  TRANS(X)*X  if requested.
	Otherwise not referenced.
	Determinant = DET(1) * 10.0**DET(2)
	with  1.0 .LE. DET(1) .LT. 10.0
	or  DET(1) .EQ.	0.0 .  Error Condition

     A division	by zero	will occur if the input	factor contains	a zero on the
     diagonal and the inverse is requested.  It	will not occur if the
     subroutines are called correctly and if SPOCO or SPOFA has	set INFO .EQ.
     0 .  LINPACK.  This version dated 08/14/78	.  Cleve Moler,	University of
     New Mexico, Argonne National Lab.	Subroutines and	Functions BLAS
     SAXPY,SSCAL Fortran MOD


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