numeric-linalg
Educational material on the SciPy implementation of numerical linear algebra algorithms
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lapack/SRC/chetri2.f | 6053B | -rw-r--r-- |
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*> \brief \b CHETRI2 * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * *> \htmlonly *> Download CHETRI2 + dependencies *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/chetri2.f"> *> [TGZ]</a> *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/chetri2.f"> *> [ZIP]</a> *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/chetri2.f"> *> [TXT]</a> *> \endhtmlonly * * Definition: * =========== * * SUBROUTINE CHETRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO ) * * .. Scalar Arguments .. * CHARACTER UPLO * INTEGER INFO, LDA, LWORK, N * .. * .. Array Arguments .. * INTEGER IPIV( * ) * COMPLEX A( LDA, * ), WORK( * ) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> CHETRI2 computes the inverse of a COMPLEX hermitian indefinite matrix *> A using the factorization A = U*D*U**T or A = L*D*L**T computed by *> CHETRF. CHETRI2 set the LEADING DIMENSION of the workspace *> before calling CHETRI2X that actually computes the inverse. *> \endverbatim * * Arguments: * ========== * *> \param[in] UPLO *> \verbatim *> 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. *> \endverbatim *> *> \param[in] N *> \verbatim *> N is INTEGER *> The order of the matrix A. N >= 0. *> \endverbatim *> *> \param[in,out] A *> \verbatim *> A is COMPLEX 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 CHETRF. *> *> 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. *> \endverbatim *> *> \param[in] LDA *> \verbatim *> LDA is INTEGER *> The leading dimension of the array A. LDA >= max(1,N). *> \endverbatim *> *> \param[in] IPIV *> \verbatim *> IPIV is INTEGER array, dimension (N) *> Details of the interchanges and the block structure of D *> as determined by CHETRF. *> \endverbatim *> *> \param[out] WORK *> \verbatim *> WORK is COMPLEX array, dimension (MAX(1,LWORK)) *> \endverbatim *> *> \param[in] LWORK *> \verbatim *> LWORK is INTEGER *> The dimension of the array WORK. *> If N = 0, LWORK >= 1, else LWORK >= (N+NB+1)*(NB+3). *> If LWORK = -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 LWORK is issued by XERBLA. *> \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, D(i,i) = 0; the matrix is singular and its *> inverse could not be computed. *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \ingroup hetri2 * * ===================================================================== SUBROUTINE CHETRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO ) * * -- LAPACK computational routine -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * * .. Scalar Arguments .. CHARACTER UPLO INTEGER INFO, LDA, LWORK, N * .. * .. Array Arguments .. INTEGER IPIV( * ) COMPLEX A( LDA, * ), WORK( * ) * .. * * ===================================================================== * * .. Local Scalars .. LOGICAL UPPER, LQUERY INTEGER MINSIZE, NBMAX * .. * .. External Functions .. LOGICAL LSAME INTEGER ILAENV REAL SROUNDUP_LWORK EXTERNAL LSAME, ILAENV, SROUNDUP_LWORK * .. * .. External Subroutines .. EXTERNAL CHETRI2X, CHETRI, XERBLA * .. * .. Executable Statements .. * * Test the input parameters. * INFO = 0 UPPER = LSAME( UPLO, 'U' ) LQUERY = ( LWORK.EQ.-1 ) * * Get blocksize * NBMAX = ILAENV( 1, 'CHETRF', UPLO, N, -1, -1, -1 ) IF( N.EQ.0 ) THEN MINSIZE = 1 ELSE IF( NBMAX.GE.N ) THEN MINSIZE = N ELSE MINSIZE = (N+NBMAX+1)*(NBMAX+3) END IF * IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN INFO = -1 ELSE IF( N.LT.0 ) THEN INFO = -2 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN INFO = -4 ELSE IF( LWORK.LT.MINSIZE .AND. .NOT.LQUERY ) THEN INFO = -7 END IF * IF( INFO.NE.0 ) THEN CALL XERBLA( 'CHETRI2', -INFO ) RETURN ELSE IF( LQUERY ) THEN WORK( 1 ) = SROUNDUP_LWORK( MINSIZE ) RETURN END IF * * Quick return if possible * IF( N.EQ.0 ) $ RETURN IF( NBMAX.GE.N ) THEN CALL CHETRI( UPLO, N, A, LDA, IPIV, WORK, INFO ) ELSE CALL CHETRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO ) END IF * RETURN * * End of CHETRI2 * END