SSPDI(3F)							     SSPDI(3F)

NAME    [Toc]    [Back]

     SSPDI   - SSPDI computes the determinant, inertia and inverse of a	real
     symmetric matrix using the	factors	from SSPFA, where the matrix is	stored
     in	packed form.

SYNOPSYS    [Toc]    [Back]

      SUBROUTINE SSPDI(AP,N,KPVT,DET,INERT,WORK,JOB)

DESCRIPTION    [Toc]    [Back]

     On	Entry

     AP	REAL (N*(N+1)/2)
	the output from	SSPFA.

     N INTEGER
	the order of the matrix	A.

     KPVT INTEGER(N)
	the pivot vector from SSPFA.

     WORK REAL(N)
	work vector.  Contents ignored.

     JOB INTEGER
	JOB has	the decimal expansion  ABC  where
	If  C .NE. 0, the inverse is computed,
	If  B .NE. 0, the determinant is computed,
	If  A .NE. 0, the inertia is computed.
	For example, JOB = 111	gives all three.  On Return Variables not
     requested by JOB are not used.

     AP	contains the upper triangle of the inverse of
	the original matrix, stored in packed form.
	The columns of the upper triangle are stored
	sequentially in	a one-dimensional array.

     DET REAL(2)
	determinant of original	matrix.
	Determinant = DET(1) * 10.0**DET(2)
	with 1.0 .LE. ABS(DET(1)) .LT. 10.0
	or DET(1) = 0.0.

     INERT INTEGER(3)
	the inertia of the original matrix.
	INERT(1)  =  number of positive	eigenvalues.
	INERT(2)  =  number of negative	eigenvalues.
	INERT(3)  =  number of zero eigenvalues.  Error	Condition

     A division	by zero	will occur if the inverse is requested and  SSPCO  has
     set RCOND .EQ. 0.0	or  SSPFA  has set  INFO .NE. 0	.  LINPACK.  This
     version dated 08/14/78 .  James Bunch, Univ. Calif. San Diego, Argonne



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SSPDI(3F)							     SSPDI(3F)



     Nat. Lab.	Subroutines and	Functions BLAS SAXPY,SCOPY,SDOT,SSWAP Fortran
     ABS,IABS,MOD


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