SUBROUTINE SSYTRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO ) * * -- LAPACK routine (version 3.3.1) -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * -- April 2011 -- * * -- Written by Julie Langou of the Univ. of TN -- * * @generated s * .. Scalar Arguments .. CHARACTER UPLO INTEGER INFO, LDA, LWORK, N * .. * .. Array Arguments .. INTEGER IPIV( * ) REAL A( LDA, * ), WORK( * ) * .. * * Purpose * ======= * * SSYTRI2 computes the inverse of a REAL hermitian indefinite matrix * A using the factorization A = U*D*U**T or A = L*D*L**T computed by * SSYTRF. SSYTRI2 sets the LEADING DIMENSION of the workspace * before calling SSYTRI2X that actually computes the inverse. * * Arguments * ========= * * UPLO (input) 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. * * N (input) INTEGER * The order of the matrix A. N >= 0. * * A (input/output) REAL array, dimension (LDA,N) * On entry, the NB diagonal matrix D and the multipliers * used to obtain the factor U or L as computed by SSYTRF. * * 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. * * LDA (input) INTEGER * The leading dimension of the array A. LDA >= max(1,N). * * IPIV (input) INTEGER array, dimension (N) * Details of the interchanges and the NB structure of D * as determined by SSYTRF. * * WORK (workspace) REAL array, dimension (N+NB+1)*(NB+3) * * LWORK (input) 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. * * INFO (output) 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. * * ===================================================================== * * .. Local Scalars .. LOGICAL UPPER, LQUERY INTEGER MINSIZE, NBMAX * .. * .. External Functions .. LOGICAL LSAME INTEGER ILAENV EXTERNAL LSAME, ILAENV * .. * .. External Subroutines .. EXTERNAL SSYTRI2X * .. * .. Executable Statements .. * * Test the input parameters. * INFO = 0 UPPER = LSAME( UPLO, 'U' ) LQUERY = ( LWORK.EQ.-1 ) * Get blocksize NBMAX = ILAENV( 1, 'SSYTRF', UPLO, N, -1, -1, -1 ) 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 * * Quick return if possible * * IF( INFO.NE.0 ) THEN CALL XERBLA( 'SSYTRI2', -INFO ) RETURN ELSE IF( LQUERY ) THEN WORK(1)=MINSIZE RETURN END IF IF( N.EQ.0 ) \$ RETURN IF( NBMAX .GE. N ) THEN CALL SSYTRI( UPLO, N, A, LDA, IPIV, WORK, INFO ) ELSE CALL SSYTRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO ) END IF RETURN * * End of SSYTRI2 * END