DSIDI(3F)							     DSIDI(3F)

NAME    [Toc]    [Back]

     DSIDI   - DSIDI computes the determinant, inertia and inverse of a	double
     precision symmetric matrix	using the factors from DSIFA.

SYNOPSYS    [Toc]    [Back]

      SUBROUTINE DSIDI(A,LDA,N,KPVT,DET,INERT,WORK,JOB)

DESCRIPTION    [Toc]    [Back]

     On	Entry

     A DOUBLE PRECISION(LDA,N)
	the output from	DSIFA.

     LDA INTEGER
	the leading dimension of the array A.

     N INTEGER
	the order of the matrix	A.

     KPVT INTEGER(N)
	the pivot vector from DSIFA.

     WORK DOUBLE PRECISION(N)
	work vector.  Contents destroyed.

     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.

     A contains	the upper triangle of the inverse of
	the original matrix.  The strict lower triangle
	is never referenced.

     DET DOUBLE	PRECISION(2)
	determinant of original	matrix.
	DETERMINANT = DET(1) * 10.0**DET(2)
	with 1.0 .LE. DABS(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	may occur if the inverse is requested and  DSICO  has
     set RCOND .EQ. 0.0	or  DSIFA  has set  INFO .NE. 0	.  LINPACK.  This



									Page 1






DSIDI(3F)							     DSIDI(3F)



     version dated 08/14/78 .  James Bunch, Univ. Calif. San Diego, Argonne
     Nat. Lab Subroutines and Functions	BLAS DAXPY,DCOPY,DDOT,DSWAP Fortran
     DABS,IABS,MOD


									PPPPaaaaggggeeee 2222