Annotation of rpl/lapack/lapack/dlauu2.f, revision 1.19
1.12 bertrand 1: *> \brief \b DLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm).
1.9 bertrand 2: *
3: * =========== DOCUMENTATION ===========
4: *
1.16 bertrand 5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
1.9 bertrand 7: *
8: *> \htmlonly
1.16 bertrand 9: *> Download DLAUU2 + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlauu2.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlauu2.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlauu2.f">
1.9 bertrand 15: *> [TXT]</a>
1.16 bertrand 16: *> \endhtmlonly
1.9 bertrand 17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE DLAUU2( UPLO, N, A, LDA, INFO )
1.16 bertrand 22: *
1.9 bertrand 23: * .. Scalar Arguments ..
24: * CHARACTER UPLO
25: * INTEGER INFO, LDA, N
26: * ..
27: * .. Array Arguments ..
28: * DOUBLE PRECISION A( LDA, * )
29: * ..
1.16 bertrand 30: *
1.9 bertrand 31: *
32: *> \par Purpose:
33: * =============
34: *>
35: *> \verbatim
36: *>
37: *> DLAUU2 computes the product U * U**T or L**T * L, where the triangular
38: *> factor U or L is stored in the upper or lower triangular part of
39: *> the array A.
40: *>
41: *> If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
42: *> overwriting the factor U in A.
43: *> If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
44: *> overwriting the factor L in A.
45: *>
46: *> This is the unblocked form of the algorithm, calling Level 2 BLAS.
47: *> \endverbatim
48: *
49: * Arguments:
50: * ==========
51: *
52: *> \param[in] UPLO
53: *> \verbatim
54: *> UPLO is CHARACTER*1
55: *> Specifies whether the triangular factor stored in the array A
56: *> is upper or lower triangular:
57: *> = 'U': Upper triangular
58: *> = 'L': Lower triangular
59: *> \endverbatim
60: *>
61: *> \param[in] N
62: *> \verbatim
63: *> N is INTEGER
64: *> The order of the triangular factor U or L. N >= 0.
65: *> \endverbatim
66: *>
67: *> \param[in,out] A
68: *> \verbatim
69: *> A is DOUBLE PRECISION array, dimension (LDA,N)
70: *> On entry, the triangular factor U or L.
71: *> On exit, if UPLO = 'U', the upper triangle of A is
72: *> overwritten with the upper triangle of the product U * U**T;
73: *> if UPLO = 'L', the lower triangle of A is overwritten with
74: *> the lower triangle of the product L**T * L.
75: *> \endverbatim
76: *>
77: *> \param[in] LDA
78: *> \verbatim
79: *> LDA is INTEGER
80: *> The leading dimension of the array A. LDA >= max(1,N).
81: *> \endverbatim
82: *>
83: *> \param[out] INFO
84: *> \verbatim
85: *> INFO is INTEGER
86: *> = 0: successful exit
87: *> < 0: if INFO = -k, the k-th argument had an illegal value
88: *> \endverbatim
89: *
90: * Authors:
91: * ========
92: *
1.16 bertrand 93: *> \author Univ. of Tennessee
94: *> \author Univ. of California Berkeley
95: *> \author Univ. of Colorado Denver
96: *> \author NAG Ltd.
1.9 bertrand 97: *
98: *> \ingroup doubleOTHERauxiliary
99: *
100: * =====================================================================
1.1 bertrand 101: SUBROUTINE DLAUU2( UPLO, N, A, LDA, INFO )
102: *
1.19 ! bertrand 103: * -- LAPACK auxiliary routine --
1.1 bertrand 104: * -- LAPACK is a software package provided by Univ. of Tennessee, --
105: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
106: *
107: * .. Scalar Arguments ..
108: CHARACTER UPLO
109: INTEGER INFO, LDA, N
110: * ..
111: * .. Array Arguments ..
112: DOUBLE PRECISION A( LDA, * )
113: * ..
114: *
115: * =====================================================================
116: *
117: * .. Parameters ..
118: DOUBLE PRECISION ONE
119: PARAMETER ( ONE = 1.0D+0 )
120: * ..
121: * .. Local Scalars ..
122: LOGICAL UPPER
123: INTEGER I
124: DOUBLE PRECISION AII
125: * ..
126: * .. External Functions ..
127: LOGICAL LSAME
128: DOUBLE PRECISION DDOT
129: EXTERNAL LSAME, DDOT
130: * ..
131: * .. External Subroutines ..
132: EXTERNAL DGEMV, DSCAL, XERBLA
133: * ..
134: * .. Intrinsic Functions ..
135: INTRINSIC MAX
136: * ..
137: * .. Executable Statements ..
138: *
139: * Test the input parameters.
140: *
141: INFO = 0
142: UPPER = LSAME( UPLO, 'U' )
143: IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
144: INFO = -1
145: ELSE IF( N.LT.0 ) THEN
146: INFO = -2
147: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
148: INFO = -4
149: END IF
150: IF( INFO.NE.0 ) THEN
151: CALL XERBLA( 'DLAUU2', -INFO )
152: RETURN
153: END IF
154: *
155: * Quick return if possible
156: *
157: IF( N.EQ.0 )
158: $ RETURN
159: *
160: IF( UPPER ) THEN
161: *
1.8 bertrand 162: * Compute the product U * U**T.
1.1 bertrand 163: *
164: DO 10 I = 1, N
165: AII = A( I, I )
166: IF( I.LT.N ) THEN
167: A( I, I ) = DDOT( N-I+1, A( I, I ), LDA, A( I, I ), LDA )
168: CALL DGEMV( 'No transpose', I-1, N-I, ONE, A( 1, I+1 ),
169: $ LDA, A( I, I+1 ), LDA, AII, A( 1, I ), 1 )
170: ELSE
171: CALL DSCAL( I, AII, A( 1, I ), 1 )
172: END IF
173: 10 CONTINUE
174: *
175: ELSE
176: *
1.8 bertrand 177: * Compute the product L**T * L.
1.1 bertrand 178: *
179: DO 20 I = 1, N
180: AII = A( I, I )
181: IF( I.LT.N ) THEN
182: A( I, I ) = DDOT( N-I+1, A( I, I ), 1, A( I, I ), 1 )
183: CALL DGEMV( 'Transpose', N-I, I-1, ONE, A( I+1, 1 ), LDA,
184: $ A( I+1, I ), 1, AII, A( I, 1 ), LDA )
185: ELSE
186: CALL DSCAL( I, AII, A( I, 1 ), LDA )
187: END IF
188: 20 CONTINUE
189: END IF
190: *
191: RETURN
192: *
193: * End of DLAUU2
194: *
195: END
CVSweb interface <joel.bertrand@systella.fr>
![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to dlauu2.f CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [local] / rpl / lapack / lapack