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  man pages->IRIX man pages -> complib/dposv (3)              
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DPOSV(3F)							     DPOSV(3F)


NAME    [Toc]    [Back]

     DPOSV - compute the solution to a real system of linear equations	A * X
     = B,

SYNOPSIS    [Toc]    [Back]

     SUBROUTINE	DPOSV( UPLO, N,	NRHS, A, LDA, B, LDB, INFO )

	 CHARACTER     UPLO

	 INTEGER       INFO, LDA, LDB, N, NRHS

	 DOUBLE	       PRECISION A( LDA, * ), B( LDB, *	)

PURPOSE    [Toc]    [Back]

     DPOSV computes the	solution to a real system of linear equations
	A * X =	B, where A is an N-by-N	symmetric positive definite matrix and
     X and B are N-by-NRHS matrices.

     The Cholesky decomposition	is used	to factor A as
	A = U**T* U,  if UPLO =	'U', or
	A = L *	L**T,  if UPLO = 'L',
     where U is	an upper triangular matrix and L is a lower triangular matrix.
     The factored form of A is then used to solve the system of	equations A *
     X = B.

ARGUMENTS    [Toc]    [Back]

     UPLO    (input) CHARACTER*1
	     = 'U':  Upper triangle of A is stored;
	     = 'L':  Lower triangle of A is stored.

     N	     (input) INTEGER
	     The number	of linear equations, i.e., the order of	the matrix A.
	     N >= 0.

     NRHS    (input) INTEGER
	     The number	of right hand sides, i.e., the number of columns of
	     the matrix	B.  NRHS >= 0.

     A	     (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	     On	entry, the symmetric matrix A.	If UPLO	= 'U', the leading Nby-N
 upper	triangular part	of A contains the upper	triangular
	     part of the matrix	A, and the strictly lower triangular part of A
	     is	not referenced.	 If UPLO = 'L',	the leading N-by-N lower
	     triangular	part of	A contains the lower triangular	part of	the
	     matrix A, and the strictly	upper triangular part of A is not
	     referenced.

	     On	exit, if INFO =	0, the factor U	or L from the Cholesky
	     factorization A = U**T*U or A = L*L**T.





									Page 1






DPOSV(3F)							     DPOSV(3F)



     LDA     (input) INTEGER
	     The leading dimension of the array	A.  LDA	>= max(1,N).

     B	     (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
	     On	entry, the N-by-NRHS right hand	side matrix B.	On exit, if
	     INFO = 0, the N-by-NRHS solution matrix X.

     LDB     (input) INTEGER
	     The leading dimension of the array	B.  LDB	>= max(1,N).

     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 of	A is not
	     positive definite,	so the factorization could not be completed,
	     and the solution has not been computed.
DPOSV(3F)							     DPOSV(3F)


NAME    [Toc]    [Back]

     DPOSV - compute the solution to a real system of linear equations	A * X
     = B,

SYNOPSIS    [Toc]    [Back]

     SUBROUTINE	DPOSV( UPLO, N,	NRHS, A, LDA, B, LDB, INFO )

	 CHARACTER     UPLO

	 INTEGER       INFO, LDA, LDB, N, NRHS

	 DOUBLE	       PRECISION A( LDA, * ), B( LDB, *	)

PURPOSE    [Toc]    [Back]

     DPOSV computes the	solution to a real system of linear equations
	A * X =	B, where A is an N-by-N	symmetric positive definite matrix and
     X and B are N-by-NRHS matrices.

     The Cholesky decomposition	is used	to factor A as
	A = U**T* U,  if UPLO =	'U', or
	A = L *	L**T,  if UPLO = 'L',
     where U is	an upper triangular matrix and L is a lower triangular matrix.
     The factored form of A is then used to solve the system of	equations A *
     X = B.

ARGUMENTS    [Toc]    [Back]

     UPLO    (input) CHARACTER*1
	     = 'U':  Upper triangle of A is stored;
	     = 'L':  Lower triangle of A is stored.

     N	     (input) INTEGER
	     The number	of linear equations, i.e., the order of	the matrix A.
	     N >= 0.

     NRHS    (input) INTEGER
	     The number	of right hand sides, i.e., the number of columns of
	     the matrix	B.  NRHS >= 0.

     A	     (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	     On	entry, the symmetric matrix A.	If UPLO	= 'U', the leading Nby-N
 upper	triangular part	of A contains the upper	triangular
	     part of the matrix	A, and the strictly lower triangular part of A
	     is	not referenced.	 If UPLO = 'L',	the leading N-by-N lower
	     triangular	part of	A contains the lower triangular	part of	the
	     matrix A, and the strictly	upper triangular part of A is not
	     referenced.

	     On	exit, if INFO =	0, the factor U	or L from the Cholesky
	     factorization A = U**T*U or A = L*L**T.





									Page 1






DPOSV(3F)							     DPOSV(3F)



     LDA     (input) INTEGER
	     The leading dimension of the array	A.  LDA	>= max(1,N).

     B	     (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
	     On	entry, the N-by-NRHS right hand	side matrix B.	On exit, if
	     INFO = 0, the N-by-NRHS solution matrix X.

     LDB     (input) INTEGER
	     The leading dimension of the array	B.  LDB	>= max(1,N).

     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 of	A is not
	     positive definite,	so the factorization could not be completed,
	     and the solution has not been computed.


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