1: SUBROUTINE ZHETRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO )
2: *
3: * -- LAPACK routine (version 3.3.1) --
4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
6: * -- April 2011 --
7: *
8: * -- Written by Julie Langou of the Univ. of TN --
9: *
10: * @precisions normal z -> c
11: *
12: * .. Scalar Arguments ..
13: CHARACTER UPLO
14: INTEGER INFO, LDA, LWORK, N
15: * ..
16: * .. Array Arguments ..
17: INTEGER IPIV( * )
18: COMPLEX*16 A( LDA, * ), WORK( * )
19: * ..
20: *
21: * Purpose
22: * =======
23: *
24: * ZHETRI2 computes the inverse of a COMPLEX*16 hermitian indefinite matrix
25: * A using the factorization A = U*D*U**T or A = L*D*L**T computed by
26: * ZHETRF. ZHETRI2 set the LEADING DIMENSION of the workspace
27: * before calling ZHETRI2X that actually computes the inverse.
28: *
29: * Arguments
30: * =========
31: *
32: * UPLO (input) CHARACTER*1
33: * Specifies whether the details of the factorization are stored
34: * as an upper or lower triangular matrix.
35: * = 'U': Upper triangular, form is A = U*D*U**T;
36: * = 'L': Lower triangular, form is A = L*D*L**T.
37: *
38: * N (input) INTEGER
39: * The order of the matrix A. N >= 0.
40: *
41: * A (input/output) COMPLEX*16 array, dimension (LDA,N)
42: * On entry, the NB diagonal matrix D and the multipliers
43: * used to obtain the factor U or L as computed by ZHETRF.
44: *
45: * On exit, if INFO = 0, the (symmetric) inverse of the original
46: * matrix. If UPLO = 'U', the upper triangular part of the
47: * inverse is formed and the part of A below the diagonal is not
48: * referenced; if UPLO = 'L' the lower triangular part of the
49: * inverse is formed and the part of A above the diagonal is
50: * not referenced.
51: *
52: * LDA (input) INTEGER
53: * The leading dimension of the array A. LDA >= max(1,N).
54: *
55: * IPIV (input) INTEGER array, dimension (N)
56: * Details of the interchanges and the NB structure of D
57: * as determined by ZHETRF.
58: *
59: * WORK (workspace) COMPLEX*16 array, dimension (N+NB+1)*(NB+3)
60: *
61: * LWORK (input) INTEGER
62: * The dimension of the array WORK.
63: * WORK is size >= (N+NB+1)*(NB+3)
64: * If LDWORK = -1, then a workspace query is assumed; the routine
65: * calculates:
66: * - the optimal size of the WORK array, returns
67: * this value as the first entry of the WORK array,
68: * - and no error message related to LDWORK is issued by XERBLA.
69: *
70: * INFO (output) INTEGER
71: * = 0: successful exit
72: * < 0: if INFO = -i, the i-th argument had an illegal value
73: * > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
74: * inverse could not be computed.
75: *
76: * =====================================================================
77: *
78: * .. Local Scalars ..
79: LOGICAL UPPER, LQUERY
80: INTEGER MINSIZE, NBMAX
81: * ..
82: * .. External Functions ..
83: LOGICAL LSAME
84: INTEGER ILAENV
85: EXTERNAL LSAME, ILAENV
86: * ..
87: * .. External Subroutines ..
88: EXTERNAL ZHETRI2X
89: * ..
90: * .. Executable Statements ..
91: *
92: * Test the input parameters.
93: *
94: INFO = 0
95: UPPER = LSAME( UPLO, 'U' )
96: LQUERY = ( LWORK.EQ.-1 )
97: * Get blocksize
98: NBMAX = ILAENV( 1, 'ZHETRF', UPLO, N, -1, -1, -1 )
99: IF ( NBMAX .GE. N ) THEN
100: MINSIZE = N
101: ELSE
102: MINSIZE = (N+NBMAX+1)*(NBMAX+3)
103: END IF
104: *
105: IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
106: INFO = -1
107: ELSE IF( N.LT.0 ) THEN
108: INFO = -2
109: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
110: INFO = -4
111: ELSE IF (LWORK .LT. MINSIZE .AND. .NOT.LQUERY ) THEN
112: INFO = -7
113: END IF
114: *
115: * Quick return if possible
116: *
117: *
118: IF( INFO.NE.0 ) THEN
119: CALL XERBLA( 'ZHETRI2', -INFO )
120: RETURN
121: ELSE IF( LQUERY ) THEN
122: WORK(1)=MINSIZE
123: RETURN
124: END IF
125: IF( N.EQ.0 )
126: $ RETURN
127:
128: IF( NBMAX .GE. N ) THEN
129: CALL ZHETRI( UPLO, N, A, LDA, IPIV, WORK, INFO )
130: ELSE
131: CALL ZHETRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO )
132: END IF
133: RETURN
134: *
135: * End of ZHETRI2
136: *
137: END
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