1: SUBROUTINE ZLAUU2( UPLO, N, A, LDA, INFO )
2: *
3: * -- LAPACK auxiliary routine (version 3.2) --
4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
6: * November 2006
7: *
8: * .. Scalar Arguments ..
9: CHARACTER UPLO
10: INTEGER INFO, LDA, N
11: * ..
12: * .. Array Arguments ..
13: COMPLEX*16 A( LDA, * )
14: * ..
15: *
16: * Purpose
17: * =======
18: *
19: * ZLAUU2 computes the product U * U' or L' * L, where the triangular
20: * factor U or L is stored in the upper or lower triangular part of
21: * the array A.
22: *
23: * If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
24: * overwriting the factor U in A.
25: * If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
26: * overwriting the factor L in A.
27: *
28: * This is the unblocked form of the algorithm, calling Level 2 BLAS.
29: *
30: * Arguments
31: * =========
32: *
33: * UPLO (input) CHARACTER*1
34: * Specifies whether the triangular factor stored in the array A
35: * is upper or lower triangular:
36: * = 'U': Upper triangular
37: * = 'L': Lower triangular
38: *
39: * N (input) INTEGER
40: * The order of the triangular factor U or L. N >= 0.
41: *
42: * A (input/output) COMPLEX*16 array, dimension (LDA,N)
43: * On entry, the triangular factor U or L.
44: * On exit, if UPLO = 'U', the upper triangle of A is
45: * overwritten with the upper triangle of the product U * U';
46: * if UPLO = 'L', the lower triangle of A is overwritten with
47: * the lower triangle of the product L' * L.
48: *
49: * LDA (input) INTEGER
50: * The leading dimension of the array A. LDA >= max(1,N).
51: *
52: * INFO (output) INTEGER
53: * = 0: successful exit
54: * < 0: if INFO = -k, the k-th argument had an illegal value
55: *
56: * =====================================================================
57: *
58: * .. Parameters ..
59: COMPLEX*16 ONE
60: PARAMETER ( ONE = ( 1.0D+0, 0.0D+0 ) )
61: * ..
62: * .. Local Scalars ..
63: LOGICAL UPPER
64: INTEGER I
65: DOUBLE PRECISION AII
66: * ..
67: * .. External Functions ..
68: LOGICAL LSAME
69: COMPLEX*16 ZDOTC
70: EXTERNAL LSAME, ZDOTC
71: * ..
72: * .. External Subroutines ..
73: EXTERNAL XERBLA, ZDSCAL, ZGEMV, ZLACGV
74: * ..
75: * .. Intrinsic Functions ..
76: INTRINSIC DBLE, DCMPLX, MAX
77: * ..
78: * .. Executable Statements ..
79: *
80: * Test the input parameters.
81: *
82: INFO = 0
83: UPPER = LSAME( UPLO, 'U' )
84: IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
85: INFO = -1
86: ELSE IF( N.LT.0 ) THEN
87: INFO = -2
88: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
89: INFO = -4
90: END IF
91: IF( INFO.NE.0 ) THEN
92: CALL XERBLA( 'ZLAUU2', -INFO )
93: RETURN
94: END IF
95: *
96: * Quick return if possible
97: *
98: IF( N.EQ.0 )
99: $ RETURN
100: *
101: IF( UPPER ) THEN
102: *
103: * Compute the product U * U'.
104: *
105: DO 10 I = 1, N
106: AII = A( I, I )
107: IF( I.LT.N ) THEN
108: A( I, I ) = AII*AII + DBLE( ZDOTC( N-I, A( I, I+1 ), LDA,
109: $ A( I, I+1 ), LDA ) )
110: CALL ZLACGV( N-I, A( I, I+1 ), LDA )
111: CALL ZGEMV( 'No transpose', I-1, N-I, ONE, A( 1, I+1 ),
112: $ LDA, A( I, I+1 ), LDA, DCMPLX( AII ),
113: $ A( 1, I ), 1 )
114: CALL ZLACGV( N-I, A( I, I+1 ), LDA )
115: ELSE
116: CALL ZDSCAL( I, AII, A( 1, I ), 1 )
117: END IF
118: 10 CONTINUE
119: *
120: ELSE
121: *
122: * Compute the product L' * L.
123: *
124: DO 20 I = 1, N
125: AII = A( I, I )
126: IF( I.LT.N ) THEN
127: A( I, I ) = AII*AII + DBLE( ZDOTC( N-I, A( I+1, I ), 1,
128: $ A( I+1, I ), 1 ) )
129: CALL ZLACGV( I-1, A( I, 1 ), LDA )
130: CALL ZGEMV( 'Conjugate transpose', N-I, I-1, ONE,
131: $ A( I+1, 1 ), LDA, A( I+1, I ), 1,
132: $ DCMPLX( AII ), A( I, 1 ), LDA )
133: CALL ZLACGV( I-1, A( I, 1 ), LDA )
134: ELSE
135: CALL ZDSCAL( I, AII, A( I, 1 ), LDA )
136: END IF
137: 20 CONTINUE
138: END IF
139: *
140: RETURN
141: *
142: * End of ZLAUU2
143: *
144: END
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