DTRDI(3F)							     DTRDI(3F)

NAME    [Toc]    [Back]

     DTRDI   - DTRDI computes the determinant and inverse of a double
     precision triangular matrix.

SYNOPSYS    [Toc]    [Back]

      SUBROUTINE DTRDI(T,LDT,N,DET,JOB,INFO)

DESCRIPTION    [Toc]    [Back]

     On	Entry

     T DOUBLE PRECISION(LDT,N)
	T contains the triangular matrix.  The zero
	elements of the	matrix are not referenced, and
	the corresponding elements of the array	can be
	used to	store other information.

     LDT INTEGER
	LDT is the leading dimension of	the array T.

     N INTEGER
	N is the order of the system.

     JOB INTEGER
	= 010	    no det, inverse of lower triangular.
	= 011	    no det, inverse of upper triangular.
	= 100	    det, no inverse.
	= 110	    det, inverse of lower triangular.
	= 111	    det, inverse of upper triangular.  On Return

     T inverse of original matrix if requested.
	Otherwise unchanged.

     DET DOUBLE	PRECISION(2)
	determinant of original	matrix if requested.
	Otherwise not referenced.
	DETERMINANT = DET(1) * 10.0**DET(2)
	with  1.0 .LE. DABS(DET(1)) .LT. 10.0
	or  DET(1) .EQ.	0.0 .

     INFO INTEGER
	INFO contains zero if the system is nonsingular
	and the	inverse	is requested.
	Otherwise INFO contains	the index of
	a zero diagonal	element	of T.  LINPACK.	 This version dated 08/14/78 .
     Cleve Moler, University of	New Mexico, Argonne National Lab.  Subroutines
     and Functions BLAS	DAXPY,DSCAL Fortran DABS,MOD


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