1: SUBROUTINE ZPOTRI( UPLO, N, A, LDA, INFO )
2: *
3: * -- LAPACK routine (version 3.2) --
4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
6: * November 2006
7: *
8: * .. Scalar Arguments ..
9: CHARACTER UPLO
10: INTEGER INFO, LDA, N
11: * ..
12: * .. Array Arguments ..
13: COMPLEX*16 A( LDA, * )
14: * ..
15: *
16: * Purpose
17: * =======
18: *
19: * ZPOTRI computes the inverse of a complex Hermitian positive definite
20: * matrix A using the Cholesky factorization A = U**H*U or A = L*L**H
21: * computed by ZPOTRF.
22: *
23: * Arguments
24: * =========
25: *
26: * UPLO (input) CHARACTER*1
27: * = 'U': Upper triangle of A is stored;
28: * = 'L': Lower triangle of A is stored.
29: *
30: * N (input) INTEGER
31: * The order of the matrix A. N >= 0.
32: *
33: * A (input/output) COMPLEX*16 array, dimension (LDA,N)
34: * On entry, the triangular factor U or L from the Cholesky
35: * factorization A = U**H*U or A = L*L**H, as computed by
36: * ZPOTRF.
37: * On exit, the upper or lower triangle of the (Hermitian)
38: * inverse of A, overwriting the input factor U or L.
39: *
40: * LDA (input) INTEGER
41: * The leading dimension of the array A. LDA >= max(1,N).
42: *
43: * INFO (output) INTEGER
44: * = 0: successful exit
45: * < 0: if INFO = -i, the i-th argument had an illegal value
46: * > 0: if INFO = i, the (i,i) element of the factor U or L is
47: * zero, and the inverse could not be computed.
48: *
49: * =====================================================================
50: *
51: * .. External Functions ..
52: LOGICAL LSAME
53: EXTERNAL LSAME
54: * ..
55: * .. External Subroutines ..
56: EXTERNAL XERBLA, ZLAUUM, ZTRTRI
57: * ..
58: * .. Intrinsic Functions ..
59: INTRINSIC MAX
60: * ..
61: * .. Executable Statements ..
62: *
63: * Test the input parameters.
64: *
65: INFO = 0
66: IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
67: INFO = -1
68: ELSE IF( N.LT.0 ) THEN
69: INFO = -2
70: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
71: INFO = -4
72: END IF
73: IF( INFO.NE.0 ) THEN
74: CALL XERBLA( 'ZPOTRI', -INFO )
75: RETURN
76: END IF
77: *
78: * Quick return if possible
79: *
80: IF( N.EQ.0 )
81: $ RETURN
82: *
83: * Invert the triangular Cholesky factor U or L.
84: *
85: CALL ZTRTRI( UPLO, 'Non-unit', N, A, LDA, INFO )
86: IF( INFO.GT.0 )
87: $ RETURN
88: *
89: * Form inv(U)*inv(U)' or inv(L)'*inv(L).
90: *
91: CALL ZLAUUM( UPLO, N, A, LDA, INFO )
92: *
93: RETURN
94: *
95: * End of ZPOTRI
96: *
97: END
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