Annotation of rpl/lapack/lapack/dlauu2.f, revision 1.9
1.9 ! bertrand 1: *> \brief \b DLAUU2
! 2: *
! 3: * =========== DOCUMENTATION ===========
! 4: *
! 5: * Online html documentation available at
! 6: * http://www.netlib.org/lapack/explore-html/
! 7: *
! 8: *> \htmlonly
! 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">
! 15: *> [TXT]</a>
! 16: *> \endhtmlonly
! 17: *
! 18: * Definition:
! 19: * ===========
! 20: *
! 21: * SUBROUTINE DLAUU2( 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: *> 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: *
! 93: *> \author Univ. of Tennessee
! 94: *> \author Univ. of California Berkeley
! 95: *> \author Univ. of Colorado Denver
! 96: *> \author NAG Ltd.
! 97: *
! 98: *> \date November 2011
! 99: *
! 100: *> \ingroup doubleOTHERauxiliary
! 101: *
! 102: * =====================================================================
1.1 bertrand 103: SUBROUTINE DLAUU2( UPLO, N, A, LDA, INFO )
104: *
1.9 ! bertrand 105: * -- LAPACK auxiliary routine (version 3.4.0) --
1.1 bertrand 106: * -- LAPACK is a software package provided by Univ. of Tennessee, --
107: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.9 ! bertrand 108: * November 2011
1.1 bertrand 109: *
110: * .. Scalar Arguments ..
111: CHARACTER UPLO
112: INTEGER INFO, LDA, N
113: * ..
114: * .. Array Arguments ..
115: DOUBLE PRECISION A( LDA, * )
116: * ..
117: *
118: * =====================================================================
119: *
120: * .. Parameters ..
121: DOUBLE PRECISION ONE
122: PARAMETER ( ONE = 1.0D+0 )
123: * ..
124: * .. Local Scalars ..
125: LOGICAL UPPER
126: INTEGER I
127: DOUBLE PRECISION AII
128: * ..
129: * .. External Functions ..
130: LOGICAL LSAME
131: DOUBLE PRECISION DDOT
132: EXTERNAL LSAME, DDOT
133: * ..
134: * .. External Subroutines ..
135: EXTERNAL DGEMV, DSCAL, XERBLA
136: * ..
137: * .. Intrinsic Functions ..
138: INTRINSIC MAX
139: * ..
140: * .. Executable Statements ..
141: *
142: * Test the input parameters.
143: *
144: INFO = 0
145: UPPER = LSAME( UPLO, 'U' )
146: IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
147: INFO = -1
148: ELSE IF( N.LT.0 ) THEN
149: INFO = -2
150: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
151: INFO = -4
152: END IF
153: IF( INFO.NE.0 ) THEN
154: CALL XERBLA( 'DLAUU2', -INFO )
155: RETURN
156: END IF
157: *
158: * Quick return if possible
159: *
160: IF( N.EQ.0 )
161: $ RETURN
162: *
163: IF( UPPER ) THEN
164: *
1.8 bertrand 165: * Compute the product U * U**T.
1.1 bertrand 166: *
167: DO 10 I = 1, N
168: AII = A( I, I )
169: IF( I.LT.N ) THEN
170: A( I, I ) = DDOT( N-I+1, A( I, I ), LDA, A( I, I ), LDA )
171: CALL DGEMV( 'No transpose', I-1, N-I, ONE, A( 1, I+1 ),
172: $ LDA, A( I, I+1 ), LDA, AII, A( 1, I ), 1 )
173: ELSE
174: CALL DSCAL( I, AII, A( 1, I ), 1 )
175: END IF
176: 10 CONTINUE
177: *
178: ELSE
179: *
1.8 bertrand 180: * Compute the product L**T * L.
1.1 bertrand 181: *
182: DO 20 I = 1, N
183: AII = A( I, I )
184: IF( I.LT.N ) THEN
185: A( I, I ) = DDOT( N-I+1, A( I, I ), 1, A( I, I ), 1 )
186: CALL DGEMV( 'Transpose', N-I, I-1, ONE, A( I+1, 1 ), LDA,
187: $ A( I+1, I ), 1, AII, A( I, 1 ), LDA )
188: ELSE
189: CALL DSCAL( I, AII, A( I, 1 ), LDA )
190: END IF
191: 20 CONTINUE
192: END IF
193: *
194: RETURN
195: *
196: * End of DLAUU2
197: *
198: END
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