LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ zposv()

subroutine zposv ( character  UPLO,
integer  N,
integer  NRHS,
complex*16, dimension( lda, * )  A,
integer  LDA,
complex*16, dimension( ldb, * )  B,
integer  LDB,
integer  INFO 
)

ZPOSV computes the solution to system of linear equations A * X = B for PO matrices

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

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

 The Cholesky decomposition is used to factor A as
    A = U**H* U,  if UPLO = 'U', or
    A = L * L**H,  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.
Parameters
[in]UPLO
          UPLO is CHARACTER*1
          = 'U':  Upper triangle of A is stored;
          = 'L':  Lower triangle of A is stored.
[in]N
          N is INTEGER
          The number of linear equations, i.e., 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]A
          A is COMPLEX*16 array, dimension (LDA,N)
          On entry, the Hermitian matrix A.  If UPLO = 'U', the leading
          N-by-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**H *U or A = L*L**H.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A.  LDA >= max(1,N).
[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 of A is not
                positive definite, so the factorization could not be
                completed, and the solution has not been computed.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 129 of file zposv.f.

130 *
131 * -- LAPACK driver routine --
132 * -- LAPACK is a software package provided by Univ. of Tennessee, --
133 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
134 *
135 * .. Scalar Arguments ..
136  CHARACTER UPLO
137  INTEGER INFO, LDA, LDB, N, NRHS
138 * ..
139 * .. Array Arguments ..
140  COMPLEX*16 A( LDA, * ), B( LDB, * )
141 * ..
142 *
143 * =====================================================================
144 *
145 * .. External Functions ..
146  LOGICAL LSAME
147  EXTERNAL lsame
148 * ..
149 * .. External Subroutines ..
150  EXTERNAL xerbla, zpotrf, zpotrs
151 * ..
152 * .. Intrinsic Functions ..
153  INTRINSIC max
154 * ..
155 * .. Executable Statements ..
156 *
157 * Test the input parameters.
158 *
159  info = 0
160  IF( .NOT.lsame( uplo, 'U' ) .AND. .NOT.lsame( uplo, 'L' ) ) THEN
161  info = -1
162  ELSE IF( n.LT.0 ) THEN
163  info = -2
164  ELSE IF( nrhs.LT.0 ) THEN
165  info = -3
166  ELSE IF( lda.LT.max( 1, n ) ) THEN
167  info = -5
168  ELSE IF( ldb.LT.max( 1, n ) ) THEN
169  info = -7
170  END IF
171  IF( info.NE.0 ) THEN
172  CALL xerbla( 'ZPOSV ', -info )
173  RETURN
174  END IF
175 *
176 * Compute the Cholesky factorization A = U**H *U or A = L*L**H.
177 *
178  CALL zpotrf( uplo, n, a, lda, info )
179  IF( info.EQ.0 ) THEN
180 *
181 * Solve the system A*X = B, overwriting B with X.
182 *
183  CALL zpotrs( uplo, n, nrhs, a, lda, b, ldb, info )
184 *
185  END IF
186  RETURN
187 *
188 * End of ZPOSV
189 *
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
subroutine zpotrs(UPLO, N, NRHS, A, LDA, B, LDB, INFO)
ZPOTRS
Definition: zpotrs.f:110
subroutine zpotrf(UPLO, N, A, LDA, INFO)
ZPOTRF VARIANT: right looking block version of the algorithm, calling Level 3 BLAS.
Definition: zpotrf.f:102
Here is the call graph for this function:
Here is the caller graph for this function: