cptsv()

subroutine cptsv	(	integer	n,
		integer	nrhs,
		real, dimension( * )	d,
		complex, dimension( * )	e,
		complex, dimension( ldb, * )	b,
		integer	ldb,
		integer	info
	)

CPTSV computes the solution to system of linear equations A * X = B for PT matrices

Download CPTSV + dependencies [TGZ] [ZIP] [TXT]

Purpose:

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

 A is factored as A = L*D*L**H, and the factored form of A is then
 used to solve the system of equations.

Parameters

[in]	N	N is INTEGER The order of the matrix A. N >= 0.
[in]	NRHS	NRHS is INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
[in,out]	D	D is 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 factorization A = L*D*L**H.
[in,out]	E	E is COMPLEX array, dimension (N-1) On entry, the (n-1) subdiagonal elements of the tridiagonal matrix A. On exit, the (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L**H factorization of A. E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the U**H*D*U factorization of A.
[in,out]	B	B is COMPLEX 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.
[in]	LDB	LDB is INTEGER The leading dimension of the array B. LDB >= max(1,N).
[out]	INFO	INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, the leading principal minor of order i is not positive, and the solution has not been computed. The factorization has not been completed unless i = N.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 114 of file cptsv.f.

*
*  -- LAPACK driver routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      INTEGER            INFO, LDB, N, NRHS
*     ..
*     .. Array Arguments ..
      REAL               D( * )
      COMPLEX            B( LDB, * ), E( * )
*     ..
*
*  =====================================================================
*
*     .. External Subroutines ..
      EXTERNAL           cpttrf, cpttrs, xerbla
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          max
*     ..
*     .. Executable Statements ..
*
*     Test the input parameters.
*
      info = 0
      IF( n.LT.0 ) THEN
         info = -1
      ELSE IF( nrhs.LT.0 ) THEN
         info = -2
      ELSE IF( ldb.LT.max( 1, n ) ) THEN
         info = -6
      END IF
      IF( info.NE.0 ) THEN
         CALL xerbla( 'CPTSV ', -info )
         RETURN
      END IF
*
*     Compute the L*D*L**H (or U**H*D*U) factorization of A.
*
      CALL cpttrf( n, d, e, info )
      IF( info.EQ.0 ) THEN
*
*        Solve the system A*X = B, overwriting B with X.
*
         CALL cpttrs( 'Lower', n, nrhs, d, e, b, ldb, info )
      END IF
      RETURN
*
*     End of CPTSV
*

Here is the call graph for this function:

Here is the caller graph for this function: