00001 SUBROUTINE DSYTRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO ) 00002 * 00003 * -- LAPACK routine (version 3.3.0) -- 00004 * -- LAPACK is a software package provided by Univ. of Tennessee, -- 00005 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 00006 * November 2010 00007 * 00008 * -- Written by Julie Langou of the Univ. of TN -- 00009 * 00010 * .. Scalar Arguments .. 00011 CHARACTER UPLO 00012 INTEGER INFO, LDA, LWORK, N 00013 * .. 00014 * .. Array Arguments .. 00015 INTEGER IPIV( * ) 00016 DOUBLE PRECISION A( LDA, * ), WORK( * ) 00017 * .. 00018 * 00019 * Purpose 00020 * ======= 00021 * 00022 * DSYTRI2 computes the inverse of a real symmetric indefinite matrix 00023 * A using the factorization A = U*D*U**T or A = L*D*L**T computed by 00024 * DSYTRF. DSYTRI2 sets the LEADING DIMENSION of the workspace 00025 * before calling DSYTRI2X that actually computes the inverse. 00026 * 00027 * Arguments 00028 * ========= 00029 * 00030 * UPLO (input) CHARACTER*1 00031 * Specifies whether the details of the factorization are stored 00032 * as an upper or lower triangular matrix. 00033 * = 'U': Upper triangular, form is A = U*D*U**T; 00034 * = 'L': Lower triangular, form is A = L*D*L**T. 00035 * 00036 * N (input) INTEGER 00037 * The order of the matrix A. N >= 0. 00038 * 00039 * A (input/output) DOUBLE PRECISION array, dimension (LDA,N) 00040 * On entry, the NB diagonal matrix D and the multipliers 00041 * used to obtain the factor U or L as computed by DSYTRF. 00042 * 00043 * On exit, if INFO = 0, the (symmetric) inverse of the original 00044 * matrix. If UPLO = 'U', the upper triangular part of the 00045 * inverse is formed and the part of A below the diagonal is not 00046 * referenced; if UPLO = 'L' the lower triangular part of the 00047 * inverse is formed and the part of A above the diagonal is 00048 * not referenced. 00049 * 00050 * LDA (input) INTEGER 00051 * The leading dimension of the array A. LDA >= max(1,N). 00052 * 00053 * IPIV (input) INTEGER array, dimension (N) 00054 * Details of the interchanges and the NB structure of D 00055 * as determined by DSYTRF. 00056 * 00057 * WORK (workspace) DOUBLE PRECISION array, dimension (N+NB+1)*(NB+3) 00058 * 00059 * LWORK (input) INTEGER 00060 * The dimension of the array WORK. 00061 * WORK is size >= (N+NB+1)*(NB+3) 00062 * If LDWORK = -1, then a workspace query is assumed; the routine 00063 * calculates: 00064 * - the optimal size of the WORK array, returns 00065 * this value as the first entry of the WORK array, 00066 * - and no error message related to LDWORK is issued by XERBLA. 00067 * 00068 * INFO (output) INTEGER 00069 * = 0: successful exit 00070 * < 0: if INFO = -i, the i-th argument had an illegal value 00071 * > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its 00072 * inverse could not be computed. 00073 * 00074 * ===================================================================== 00075 * 00076 * .. Local Scalars .. 00077 LOGICAL UPPER, LQUERY 00078 INTEGER MINSIZE, NBMAX 00079 * .. 00080 * .. External Functions .. 00081 LOGICAL LSAME 00082 INTEGER ILAENV 00083 EXTERNAL LSAME, ILAENV 00084 * .. 00085 * .. External Subroutines .. 00086 EXTERNAL DSYTRI2X 00087 * .. 00088 * .. Executable Statements .. 00089 * 00090 * Test the input parameters. 00091 * 00092 INFO = 0 00093 UPPER = LSAME( UPLO, 'U' ) 00094 LQUERY = ( LWORK.EQ.-1 ) 00095 * Get blocksize 00096 NBMAX = ILAENV( 1, 'DSYTRF', UPLO, N, -1, -1, -1 ) 00097 MINSIZE = (N+NBMAX+1)*(NBMAX+3) 00098 * 00099 IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN 00100 INFO = -1 00101 ELSE IF( N.LT.0 ) THEN 00102 INFO = -2 00103 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN 00104 INFO = -4 00105 ELSE IF (LWORK .LT. MINSIZE .AND. .NOT.LQUERY ) THEN 00106 INFO = -7 00107 END IF 00108 * 00109 * Quick return if possible 00110 * 00111 * 00112 IF( INFO.NE.0 ) THEN 00113 CALL XERBLA( 'DSYTRI2', -INFO ) 00114 RETURN 00115 ELSE IF( LQUERY ) THEN 00116 WORK(1)=(N+NBMAX+1)*(NBMAX+3) 00117 RETURN 00118 END IF 00119 IF( N.EQ.0 ) 00120 $ RETURN 00121 00122 CALL DSYTRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO ) 00123 RETURN 00124 * 00125 * End of DSYTRI2 00126 * 00127 END
1.7.2