*> \brief ZPTSV computes the solution to system of linear equations A * X = B for PT matrices * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * *> \htmlonly *> Download ZPTSV + dependencies *> *> [TGZ] *> *> [ZIP] *> *> [TXT] *> \endhtmlonly * * Definition: * =========== * * SUBROUTINE ZPTSV( N, NRHS, D, E, B, LDB, INFO ) * * .. Scalar Arguments .. * INTEGER INFO, LDB, N, NRHS * .. * .. Array Arguments .. * DOUBLE PRECISION D( * ) * COMPLEX*16 B( LDB, * ), E( * ) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> ZPTSV 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. *> \endverbatim * * Arguments: * ========== * *> \param[in] N *> \verbatim *> N is INTEGER *> The order of the matrix A. N >= 0. *> \endverbatim *> *> \param[in] NRHS *> \verbatim *> NRHS is INTEGER *> The number of right hand sides, i.e., the number of columns *> of the matrix B. NRHS >= 0. *> \endverbatim *> *> \param[in,out] D *> \verbatim *> D is DOUBLE PRECISION 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. *> \endverbatim *> *> \param[in,out] E *> \verbatim *> E is COMPLEX*16 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. *> \endverbatim *> *> \param[in,out] B *> \verbatim *> B is COMPLEX*16 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. *> \endverbatim *> *> \param[in] LDB *> \verbatim *> LDB is INTEGER *> The leading dimension of the array B. LDB >= max(1,N). *> \endverbatim *> *> \param[out] INFO *> \verbatim *> INFO is 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, and the solution has not been *> computed. The factorization has not been completed *> unless i = N. *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \ingroup complex16PTsolve * * ===================================================================== SUBROUTINE ZPTSV( N, NRHS, D, E, B, LDB, INFO ) * * -- 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 .. DOUBLE PRECISION D( * ) COMPLEX*16 B( LDB, * ), E( * ) * .. * * ===================================================================== * * .. External Subroutines .. EXTERNAL XERBLA, ZPTTRF, ZPTTRS * .. * .. 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( 'ZPTSV ', -INFO ) RETURN END IF * * Compute the L*D*L**H (or U**H*D*U) factorization of A. * CALL ZPTTRF( N, D, E, INFO ) IF( INFO.EQ.0 ) THEN * * Solve the system A*X = B, overwriting B with X. * CALL ZPTTRS( 'Lower', N, NRHS, D, E, B, LDB, INFO ) END IF RETURN * * End of ZPTSV * END