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  man pages->IRIX man pages -> complib/spttrf (3)              
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SPTTRF(3F)							    SPTTRF(3F)


NAME    [Toc]    [Back]

     SPTTRF - compute the factorization	of a real symmetric positive definite
     tridiagonal matrix	A

SYNOPSIS    [Toc]    [Back]

     SUBROUTINE	SPTTRF(	N, D, E, INFO )

	 INTEGER	INFO, N

	 REAL		D( * ),	E( * )

PURPOSE    [Toc]    [Back]

     SPTTRF computes the factorization of a real symmetric positive definite
     tridiagonal matrix	A.

     If	the subdiagonal	elements of A are supplied in the array	E, the
     factorization has the form	A = L*D*L**T, where D is diagonal and L	is
     unit lower	bidiagonal; if the superdiagonal elements of A are supplied,
     it	has the	form A = U**T*D*U, where U is unit upper bidiagonal.  (The two
     forms are equivalent if A is real.)

ARGUMENTS    [Toc]    [Back]

     N	     (input) INTEGER
	     The order of the matrix A.	 N >= 0.

     D	     (input/output) REAL array,	dimension (N)
	     On	entry, the n diagonal elements of the tridiagonal matrix A.
	     On	exit, the n diagonal elements of the diagonal matrix D from
	     the L*D*L**T factorization	of A.

     E	     (input/output) REAL array,	dimension (N-1)
	     On	entry, the (n-1) off-diagonal elements of the tridiagonal
	     matrix A.	On exit, the (n-1) off-diagonal	elements of the	unit
	     bidiagonal	factor L or U from the factorization of	A.

     INFO    (output) INTEGER
	     = 0:  successful exit
	     < 0:  if INFO = -i, the i-th argument had an illegal value
	     > 0:  if INFO = i,	the leading minor of order i is	not positive
	     definite; if i < N, the factorization could not be	completed,
	     while if i	= N, the factorization was completed, but D(N) = 0.
SPTTRF(3F)							    SPTTRF(3F)


NAME    [Toc]    [Back]

     SPTTRF - compute the factorization	of a real symmetric positive definite
     tridiagonal matrix	A

SYNOPSIS    [Toc]    [Back]

     SUBROUTINE	SPTTRF(	N, D, E, INFO )

	 INTEGER	INFO, N

	 REAL		D( * ),	E( * )

PURPOSE    [Toc]    [Back]

     SPTTRF computes the factorization of a real symmetric positive definite
     tridiagonal matrix	A.

     If	the subdiagonal	elements of A are supplied in the array	E, the
     factorization has the form	A = L*D*L**T, where D is diagonal and L	is
     unit lower	bidiagonal; if the superdiagonal elements of A are supplied,
     it	has the	form A = U**T*D*U, where U is unit upper bidiagonal.  (The two
     forms are equivalent if A is real.)

ARGUMENTS    [Toc]    [Back]

     N	     (input) INTEGER
	     The order of the matrix A.	 N >= 0.

     D	     (input/output) REAL array,	dimension (N)
	     On	entry, the n diagonal elements of the tridiagonal matrix A.
	     On	exit, the n diagonal elements of the diagonal matrix D from
	     the L*D*L**T factorization	of A.

     E	     (input/output) REAL array,	dimension (N-1)
	     On	entry, the (n-1) off-diagonal elements of the tridiagonal
	     matrix A.	On exit, the (n-1) off-diagonal	elements of the	unit
	     bidiagonal	factor L or U from the factorization of	A.

     INFO    (output) INTEGER
	     = 0:  successful exit
	     < 0:  if INFO = -i, the i-th argument had an illegal value
	     > 0:  if INFO = i,	the leading minor of order i is	not positive
	     definite; if i < N, the factorization could not be	completed,
	     while if i	= N, the factorization was completed, but D(N) = 0.


									PPPPaaaaggggeeee 1111
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