LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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◆ zsytri2()

subroutine zsytri2 ( character  UPLO,
integer  N,
complex*16, dimension( lda, * )  A,
integer  LDA,
integer, dimension( * )  IPIV,
complex*16, dimension( * )  WORK,
integer  LWORK,
integer  INFO 
)

ZSYTRI2

Download ZSYTRI2 + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 ZSYTRI2 computes the inverse of a COMPLEX*16 symmetric indefinite matrix
 A using the factorization A = U*D*U**T or A = L*D*L**T computed by
 ZSYTRF. ZSYTRI2 sets the LEADING DIMENSION of the workspace
 before calling ZSYTRI2X that actually computes the inverse.
Parameters
[in]UPLO
          UPLO is CHARACTER*1
          Specifies whether the details of the factorization are stored
          as an upper or lower triangular matrix.
          = 'U':  Upper triangular, form is A = U*D*U**T;
          = 'L':  Lower triangular, form is A = L*D*L**T.
[in]N
          N is INTEGER
          The order of the matrix A.  N >= 0.
[in,out]A
          A is COMPLEX*16 array, dimension (LDA,N)
          On entry, the block diagonal matrix D and the multipliers
          used to obtain the factor U or L as computed by ZSYTRF.

          On exit, if INFO = 0, the (symmetric) inverse of the original
          matrix.  If UPLO = 'U', the upper triangular part of the
          inverse is formed and the part of A below the diagonal is not
          referenced; if UPLO = 'L' the lower triangular part of the
          inverse is formed and the part of A above the diagonal is
          not referenced.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A.  LDA >= max(1,N).
[in]IPIV
          IPIV is INTEGER array, dimension (N)
          Details of the interchanges and the block structure of D
          as determined by ZSYTRF.
[out]WORK
          WORK is COMPLEX*16 array, dimension (N+NB+1)*(NB+3)
[in]LWORK
          LWORK is INTEGER
          The dimension of the array WORK.
          WORK is size >= (N+NB+1)*(NB+3)
          If LDWORK = -1, then a workspace query is assumed; the routine
           calculates:
              - the optimal size of the WORK array, returns
          this value as the first entry of the WORK array,
              - and no error message related to LDWORK is issued by XERBLA.
[out]INFO
          INFO is INTEGER
          = 0: successful exit
          < 0: if INFO = -i, the i-th argument had an illegal value
          > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
               inverse could not be computed.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 126 of file zsytri2.f.

127*
128* -- LAPACK computational routine --
129* -- LAPACK is a software package provided by Univ. of Tennessee, --
130* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
131*
132* .. Scalar Arguments ..
133 CHARACTER UPLO
134 INTEGER INFO, LDA, LWORK, N
135* ..
136* .. Array Arguments ..
137 INTEGER IPIV( * )
138 COMPLEX*16 A( LDA, * ), WORK( * )
139* ..
140*
141* =====================================================================
142*
143* .. Local Scalars ..
144 LOGICAL UPPER, LQUERY
145 INTEGER MINSIZE, NBMAX
146* ..
147* .. External Functions ..
148 LOGICAL LSAME
149 INTEGER ILAENV
150 EXTERNAL lsame, ilaenv
151* ..
152* .. External Subroutines ..
153 EXTERNAL zsytri, zsytri2x, xerbla
154* ..
155* .. Executable Statements ..
156*
157* Test the input parameters.
158*
159 info = 0
160 upper = lsame( uplo, 'U' )
161 lquery = ( lwork.EQ.-1 )
162* Get blocksize
163 nbmax = ilaenv( 1, 'ZSYTRI2', uplo, n, -1, -1, -1 )
164 IF ( nbmax .GE. n ) THEN
165 minsize = n
166 ELSE
167 minsize = (n+nbmax+1)*(nbmax+3)
168 END IF
169*
170 IF( .NOT.upper .AND. .NOT.lsame( uplo, 'L' ) ) THEN
171 info = -1
172 ELSE IF( n.LT.0 ) THEN
173 info = -2
174 ELSE IF( lda.LT.max( 1, n ) ) THEN
175 info = -4
176 ELSE IF (lwork .LT. minsize .AND. .NOT.lquery ) THEN
177 info = -7
178 END IF
179*
180* Quick return if possible
181*
182*
183 IF( info.NE.0 ) THEN
184 CALL xerbla( 'ZSYTRI2', -info )
185 RETURN
186 ELSE IF( lquery ) THEN
187 work(1)=minsize
188 RETURN
189 END IF
190 IF( n.EQ.0 )
191 $ RETURN
192
193 IF( nbmax .GE. n ) THEN
194 CALL zsytri( uplo, n, a, lda, ipiv, work, info )
195 ELSE
196 CALL zsytri2x( uplo, n, a, lda, ipiv, work, nbmax, info )
197 END IF
198 RETURN
199*
200* End of ZSYTRI2
201*
integer function ilaenv(ISPEC, NAME, OPTS, N1, N2, N3, N4)
ILAENV
Definition: ilaenv.f:162
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
subroutine zsytri2x(UPLO, N, A, LDA, IPIV, WORK, NB, INFO)
ZSYTRI2X
Definition: zsytri2x.f:120
subroutine zsytri(UPLO, N, A, LDA, IPIV, WORK, INFO)
ZSYTRI
Definition: zsytri.f:114
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