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LAPACK 3.3.1
Linear Algebra PACKage
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LAPACK 3.3.1
Linear Algebra PACKage
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00001 SUBROUTINE SSYTRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO ) 00002 * 00003 * -- LAPACK routine (version 3.3.1) -- 00004 * -- LAPACK is a software package provided by Univ. of Tennessee, -- 00005 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 00006 * -- April 2011 -- 00007 * 00008 * -- Written by Julie Langou of the Univ. of TN -- 00009 * 00010 * @generated s 00011 * .. Scalar Arguments .. 00012 CHARACTER UPLO 00013 INTEGER INFO, LDA, LWORK, N 00014 * .. 00015 * .. Array Arguments .. 00016 INTEGER IPIV( * ) 00017 REAL A( LDA, * ), WORK( * ) 00018 * .. 00019 * 00020 * Purpose 00021 * ======= 00022 * 00023 * SSYTRI2 computes the inverse of a REAL hermitian indefinite matrix 00024 * A using the factorization A = U*D*U**T or A = L*D*L**T computed by 00025 * SSYTRF. SSYTRI2 sets the LEADING DIMENSION of the workspace 00026 * before calling SSYTRI2X that actually computes the inverse. 00027 * 00028 * Arguments 00029 * ========= 00030 * 00031 * UPLO (input) CHARACTER*1 00032 * Specifies whether the details of the factorization are stored 00033 * as an upper or lower triangular matrix. 00034 * = 'U': Upper triangular, form is A = U*D*U**T; 00035 * = 'L': Lower triangular, form is A = L*D*L**T. 00036 * 00037 * N (input) INTEGER 00038 * The order of the matrix A. N >= 0. 00039 * 00040 * A (input/output) REAL array, dimension (LDA,N) 00041 * On entry, the NB diagonal matrix D and the multipliers 00042 * used to obtain the factor U or L as computed by SSYTRF. 00043 * 00044 * On exit, if INFO = 0, the (symmetric) inverse of the original 00045 * matrix. If UPLO = 'U', the upper triangular part of the 00046 * inverse is formed and the part of A below the diagonal is not 00047 * referenced; if UPLO = 'L' the lower triangular part of the 00048 * inverse is formed and the part of A above the diagonal is 00049 * not referenced. 00050 * 00051 * LDA (input) INTEGER 00052 * The leading dimension of the array A. LDA >= max(1,N). 00053 * 00054 * IPIV (input) INTEGER array, dimension (N) 00055 * Details of the interchanges and the NB structure of D 00056 * as determined by SSYTRF. 00057 * 00058 * WORK (workspace) REAL array, dimension (N+NB+1)*(NB+3) 00059 * 00060 * LWORK (input) INTEGER 00061 * The dimension of the array WORK. 00062 * WORK is size >= (N+NB+1)*(NB+3) 00063 * If LDWORK = -1, then a workspace query is assumed; the routine 00064 * calculates: 00065 * - the optimal size of the WORK array, returns 00066 * this value as the first entry of the WORK array, 00067 * - and no error message related to LDWORK is issued by XERBLA. 00068 * 00069 * INFO (output) INTEGER 00070 * = 0: successful exit 00071 * < 0: if INFO = -i, the i-th argument had an illegal value 00072 * > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its 00073 * inverse could not be computed. 00074 * 00075 * ===================================================================== 00076 * 00077 * .. Local Scalars .. 00078 LOGICAL UPPER, LQUERY 00079 INTEGER MINSIZE, NBMAX 00080 * .. 00081 * .. External Functions .. 00082 LOGICAL LSAME 00083 INTEGER ILAENV 00084 EXTERNAL LSAME, ILAENV 00085 * .. 00086 * .. External Subroutines .. 00087 EXTERNAL SSYTRI2X 00088 * .. 00089 * .. Executable Statements .. 00090 * 00091 * Test the input parameters. 00092 * 00093 INFO = 0 00094 UPPER = LSAME( UPLO, 'U' ) 00095 LQUERY = ( LWORK.EQ.-1 ) 00096 * Get blocksize 00097 NBMAX = ILAENV( 1, 'SSYTRF', UPLO, N, -1, -1, -1 ) 00098 IF ( NBMAX .GE. N ) THEN 00099 MINSIZE = N 00100 ELSE 00101 MINSIZE = (N+NBMAX+1)*(NBMAX+3) 00102 END IF 00103 * 00104 IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN 00105 INFO = -1 00106 ELSE IF( N.LT.0 ) THEN 00107 INFO = -2 00108 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN 00109 INFO = -4 00110 ELSE IF (LWORK .LT. MINSIZE .AND. .NOT.LQUERY ) THEN 00111 INFO = -7 00112 END IF 00113 * 00114 * Quick return if possible 00115 * 00116 * 00117 IF( INFO.NE.0 ) THEN 00118 CALL XERBLA( 'SSYTRI2', -INFO ) 00119 RETURN 00120 ELSE IF( LQUERY ) THEN 00121 WORK(1)=MINSIZE 00122 RETURN 00123 END IF 00124 IF( N.EQ.0 ) 00125 $ RETURN 00126 00127 IF( NBMAX .GE. N ) THEN 00128 CALL SSYTRI( UPLO, N, A, LDA, IPIV, WORK, INFO ) 00129 ELSE 00130 CALL SSYTRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO ) 00131 END IF 00132 RETURN 00133 * 00134 * End of SSYTRI2 00135 * 00136 END
1.7.3 
