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
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dpotri.f">
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: *> \date November 2011
92: *
93: *> \ingroup doublePOcomputational
94: *
95: * =====================================================================
96: SUBROUTINE DPOTRI( UPLO, N, A, LDA, INFO )
97: *
98: * -- LAPACK computational routine (version 3.4.0) --
99: * -- LAPACK is a software package provided by Univ. of Tennessee, --
100: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
101: * November 2011
102: *
103: * .. Scalar Arguments ..
104: CHARACTER UPLO
105: INTEGER INFO, LDA, N
106: * ..
107: * .. Array Arguments ..
108: DOUBLE PRECISION A( LDA, * )
109: * ..
110: *
111: * =====================================================================
112: *
113: * .. External Functions ..
114: LOGICAL LSAME
115: EXTERNAL LSAME
116: * ..
117: * .. External Subroutines ..
118: EXTERNAL DLAUUM, DTRTRI, XERBLA
119: * ..
120: * .. Intrinsic Functions ..
121: INTRINSIC MAX
122: * ..
123: * .. Executable Statements ..
124: *
125: * Test the input parameters.
126: *
127: INFO = 0
128: IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
129: INFO = -1
130: ELSE IF( N.LT.0 ) THEN
131: INFO = -2
132: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
133: INFO = -4
134: END IF
135: IF( INFO.NE.0 ) THEN
136: CALL XERBLA( 'DPOTRI', -INFO )
137: RETURN
138: END IF
139: *
140: * Quick return if possible
141: *
142: IF( N.EQ.0 )
143: $ RETURN
144: *
145: * Invert the triangular Cholesky factor U or L.
146: *
147: CALL DTRTRI( UPLO, 'Non-unit', N, A, LDA, INFO )
148: IF( INFO.GT.0 )
149: $ RETURN
150: *
151: * Form inv(U) * inv(U)**T or inv(L)**T * inv(L).
152: *
153: CALL DLAUUM( UPLO, N, A, LDA, INFO )
154: *
155: RETURN
156: *
157: * End of DPOTRI
158: *
159: END
CVSweb interface <joel.bertrand@systella.fr>