 LAPACK  3.10.1 LAPACK: Linear Algebra PACKage

## ◆ zptsv()

 subroutine zptsv ( integer N, integer NRHS, double precision, dimension( * ) D, complex*16, dimension( * ) E, complex*16, dimension( ldb, * ) B, integer LDB, integer INFO )

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

Purpose:
``` 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.```
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 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.``` [in,out] E ``` 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.``` [in,out] B ``` 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.``` [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 minor of order i is not positive definite, and the solution has not been computed. The factorization has not been completed unless i = N.```

Definition at line 114 of file zptsv.f.

115 *
116 * -- LAPACK driver routine --
117 * -- LAPACK is a software package provided by Univ. of Tennessee, --
118 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
119 *
120 * .. Scalar Arguments ..
121  INTEGER INFO, LDB, N, NRHS
122 * ..
123 * .. Array Arguments ..
124  DOUBLE PRECISION D( * )
125  COMPLEX*16 B( LDB, * ), E( * )
126 * ..
127 *
128 * =====================================================================
129 *
130 * .. External Subroutines ..
131  EXTERNAL xerbla, zpttrf, zpttrs
132 * ..
133 * .. Intrinsic Functions ..
134  INTRINSIC max
135 * ..
136 * .. Executable Statements ..
137 *
138 * Test the input parameters.
139 *
140  info = 0
141  IF( n.LT.0 ) THEN
142  info = -1
143  ELSE IF( nrhs.LT.0 ) THEN
144  info = -2
145  ELSE IF( ldb.LT.max( 1, n ) ) THEN
146  info = -6
147  END IF
148  IF( info.NE.0 ) THEN
149  CALL xerbla( 'ZPTSV ', -info )
150  RETURN
151  END IF
152 *
153 * Compute the L*D*L**H (or U**H*D*U) factorization of A.
154 *
155  CALL zpttrf( n, d, e, info )
156  IF( info.EQ.0 ) THEN
157 *
158 * Solve the system A*X = B, overwriting B with X.
159 *
160  CALL zpttrs( 'Lower', n, nrhs, d, e, b, ldb, info )
161  END IF
162  RETURN
163 *
164 * End of ZPTSV
165 *
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
subroutine zpttrs(UPLO, N, NRHS, D, E, B, LDB, INFO)
ZPTTRS
Definition: zpttrs.f:121
subroutine zpttrf(N, D, E, INFO)
ZPTTRF
Definition: zpttrf.f:92
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