LAPACK  3.10.0
LAPACK: Linear Algebra PACKage
dpotri.f
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1 *> \brief \b DPOTRI
2 *
3 * =========== DOCUMENTATION ===========
4 *
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
7 *
8 *> \htmlonly
9 *> Download DPOTRI + dependencies
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11 *> [TGZ]</a>
12 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dpotri.f">
13 *> [ZIP]</a>
14 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dpotri.f">
15 *> [TXT]</a>
16 *> \endhtmlonly
17 *
18 * Definition:
19 * ===========
20 *
21 * SUBROUTINE DPOTRI( UPLO, N, A, LDA, INFO )
22 *
23 * .. Scalar Arguments ..
24 * CHARACTER UPLO
25 * INTEGER INFO, LDA, N
26 * ..
27 * .. Array Arguments ..
28 * DOUBLE PRECISION A( LDA, * )
29 * ..
30 *
31 *
32 *> \par Purpose:
33 * =============
34 *>
35 *> \verbatim
36 *>
37 *> DPOTRI computes the inverse of a real symmetric positive definite
38 *> matrix A using the Cholesky factorization A = U**T*U or A = L*L**T
39 *> computed by DPOTRF.
40 *> \endverbatim
41 *
42 * Arguments:
43 * ==========
44 *
45 *> \param[in] UPLO
46 *> \verbatim
47 *> UPLO is CHARACTER*1
48 *> = 'U': Upper triangle of A is stored;
49 *> = 'L': Lower triangle of A is stored.
50 *> \endverbatim
51 *>
52 *> \param[in] N
53 *> \verbatim
54 *> N is INTEGER
55 *> The order of the matrix A. N >= 0.
56 *> \endverbatim
57 *>
58 *> \param[in,out] A
59 *> \verbatim
60 *> A is DOUBLE PRECISION array, dimension (LDA,N)
61 *> On entry, the triangular factor U or L from the Cholesky
62 *> factorization A = U**T*U or A = L*L**T, as computed by
63 *> DPOTRF.
64 *> On exit, the upper or lower triangle of the (symmetric)
65 *> inverse of A, overwriting the input factor U or L.
66 *> \endverbatim
67 *>
68 *> \param[in] LDA
69 *> \verbatim
70 *> LDA is INTEGER
71 *> The leading dimension of the array A. LDA >= max(1,N).
72 *> \endverbatim
73 *>
74 *> \param[out] INFO
75 *> \verbatim
76 *> INFO is INTEGER
77 *> = 0: successful exit
78 *> < 0: if INFO = -i, the i-th argument had an illegal value
79 *> > 0: if INFO = i, the (i,i) element of the factor U or L is
80 *> zero, and the inverse could not be computed.
81 *> \endverbatim
82 *
83 * Authors:
84 * ========
85 *
86 *> \author Univ. of Tennessee
87 *> \author Univ. of California Berkeley
88 *> \author Univ. of Colorado Denver
89 *> \author NAG Ltd.
90 *
91 *> \ingroup doublePOcomputational
92 *
93 * =====================================================================
94  SUBROUTINE dpotri( UPLO, N, A, LDA, INFO )
95 *
96 * -- LAPACK computational routine --
97 * -- LAPACK is a software package provided by Univ. of Tennessee, --
98 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
99 *
100 * .. Scalar Arguments ..
101  CHARACTER UPLO
102  INTEGER INFO, LDA, N
103 * ..
104 * .. Array Arguments ..
105  DOUBLE PRECISION A( LDA, * )
106 * ..
107 *
108 * =====================================================================
109 *
110 * .. External Functions ..
111  LOGICAL LSAME
112  EXTERNAL lsame
113 * ..
114 * .. External Subroutines ..
115  EXTERNAL dlauum, dtrtri, xerbla
116 * ..
117 * .. Intrinsic Functions ..
118  INTRINSIC max
119 * ..
120 * .. Executable Statements ..
121 *
122 * Test the input parameters.
123 *
124  info = 0
125  IF( .NOT.lsame( uplo, 'U' ) .AND. .NOT.lsame( uplo, 'L' ) ) THEN
126  info = -1
127  ELSE IF( n.LT.0 ) THEN
128  info = -2
129  ELSE IF( lda.LT.max( 1, n ) ) THEN
130  info = -4
131  END IF
132  IF( info.NE.0 ) THEN
133  CALL xerbla( 'DPOTRI', -info )
134  RETURN
135  END IF
136 *
137 * Quick return if possible
138 *
139  IF( n.EQ.0 )
140  $ RETURN
141 *
142 * Invert the triangular Cholesky factor U or L.
143 *
144  CALL dtrtri( uplo, 'Non-unit', n, a, lda, info )
145  IF( info.GT.0 )
146  $ RETURN
147 *
148 * Form inv(U) * inv(U)**T or inv(L)**T * inv(L).
149 *
150  CALL dlauum( uplo, n, a, lda, info )
151 *
152  RETURN
153 *
154 * End of DPOTRI
155 *
156  END
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
subroutine dlauum(UPLO, N, A, LDA, INFO)
DLAUUM computes the product UUH or LHL, where U and L are upper or lower triangular matrices (blocked...
Definition: dlauum.f:102
subroutine dtrtri(UPLO, DIAG, N, A, LDA, INFO)
DTRTRI
Definition: dtrtri.f:109
subroutine dpotri(UPLO, N, A, LDA, INFO)
DPOTRI
Definition: dpotri.f:95