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Diffstat (limited to 'SRC/dsytri2.f')
| -rw-r--r-- | SRC/dsytri2.f | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/SRC/dsytri2.f b/SRC/dsytri2.f new file mode 100644 index 00000000..c04a0bd0 --- /dev/null +++ b/SRC/dsytri2.f @@ -0,0 +1,127 @@ + SUBROUTINE DSYTRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO ) +* +* -- LAPACK routine (version 3.3.0) -- +* -- LAPACK is a software package provided by Univ. of Tennessee, -- +* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- +* November 2010 +* +* -- Written by Julie Langou of the Univ. of TN -- +* +* .. Scalar Arguments .. + CHARACTER UPLO + INTEGER INFO, LDA, LWORK, N +* .. +* .. Array Arguments .. + INTEGER IPIV( * ) + DOUBLE PRECISION A( LDA, * ), WORK( * ) +* .. +* +* Purpose +* ======= +* +* DSYTRI2 computes the inverse of a real symmetric indefinite matrix +* A using the factorization A = U*D*U**T or A = L*D*L**T computed by +* DSYTRF. DSYTRI2 set the LEADING DIMENSION of the workspace +* before calling DSYTRI2X that actually compute 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) DOUBLE PRECISION 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 DSYTRF. +* +* 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 DSYTRF. +* +* WORK (workspace) DOUBLE PRECISION 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 DSYTRI2X +* .. +* .. Executable Statements .. +* +* Test the input parameters. +* + INFO = 0 + UPPER = LSAME( UPLO, 'U' ) + LQUERY = ( LWORK.EQ.-1 ) +* Get blocksize + NBMAX = ILAENV( 1, 'DSYTRF', UPLO, N, -1, -1, -1 ) + MINSIZE = (N+NBMAX+1)*(NBMAX+3) +* + 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( 'DSYTRI2', -INFO ) + RETURN + ELSE IF( LQUERY ) THEN + WORK(1)=(N+NBMAX+1)*(NBMAX+3) + RETURN + END IF + IF( N.EQ.0 ) + $ RETURN + + CALL DSYTRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO ) + RETURN +* +* End of DSYTRI2 +* + END |