1 SUBROUTINE DPOTRI( UPLO, N, A, LDA, 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 * .. Scalar Arguments ..
9 CHARACTER UPLO
10 INTEGER INFO, LDA, N
11 * ..
12 * .. Array Arguments ..
13 DOUBLE PRECISION A( LDA, * )
14 * ..
15 *
16 * Purpose
17 * =======
18 *
19 * DPOTRI computes the inverse of a real symmetric positive definite
20 * matrix A using the Cholesky factorization A = U**T*U or A = L*L**T
21 * computed by DPOTRF.
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) DOUBLE PRECISION array, dimension (LDA,N)
34 * On entry, the triangular factor U or L from the Cholesky
35 * factorization A = U**T*U or A = L*L**T, as computed by
36 * DPOTRF.
37 * On exit, the upper or lower triangle of the (symmetric)
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 DLAUUM, DTRTRI, XERBLA
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( 'DPOTRI', -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 DTRTRI( UPLO, 'Non-unit', N, A, LDA, INFO )
86 IF( INFO.GT.0 )
87 $ RETURN
88 *
89 * Form inv(U) * inv(U)**T or inv(L)**T * inv(L).
90 *
91 CALL DLAUUM( UPLO, N, A, LDA, INFO )
92 *
93 RETURN
94 *
95 * End of DPOTRI
96 *
97 END
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 * .. Scalar Arguments ..
9 CHARACTER UPLO
10 INTEGER INFO, LDA, N
11 * ..
12 * .. Array Arguments ..
13 DOUBLE PRECISION A( LDA, * )
14 * ..
15 *
16 * Purpose
17 * =======
18 *
19 * DPOTRI computes the inverse of a real symmetric positive definite
20 * matrix A using the Cholesky factorization A = U**T*U or A = L*L**T
21 * computed by DPOTRF.
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) DOUBLE PRECISION array, dimension (LDA,N)
34 * On entry, the triangular factor U or L from the Cholesky
35 * factorization A = U**T*U or A = L*L**T, as computed by
36 * DPOTRF.
37 * On exit, the upper or lower triangle of the (symmetric)
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 DLAUUM, DTRTRI, XERBLA
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( 'DPOTRI', -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 DTRTRI( UPLO, 'Non-unit', N, A, LDA, INFO )
86 IF( INFO.GT.0 )
87 $ RETURN
88 *
89 * Form inv(U) * inv(U)**T or inv(L)**T * inv(L).
90 *
91 CALL DLAUUM( UPLO, N, A, LDA, INFO )
92 *
93 RETURN
94 *
95 * End of DPOTRI
96 *
97 END