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comparison libcruft/lapack/cung2r.f @ 7789:82be108cc558

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First attempt at single precision tyeps * * * corrections to qrupdate single precision routines * * * prefer demotion to single over promotion to double * * * Add single precision support to log2 function * * * Trivial PROJECT file update * * * Cache optimized hermitian/transpose methods * * * Add tests for tranpose/hermitian and ChangeLog entry for new transpose code
author David Bateman <dbateman@free.fr>
date Sun, 27 Apr 2008 22:34:17 +0200
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7788:45f5faba05a2 7789:82be108cc558
1 SUBROUTINE CUNG2R( M, N, K, A, LDA, TAU, WORK, INFO )
2 *
3 * -- LAPACK routine (version 3.1) --
4 * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
5 * November 2006
6 *
7 * .. Scalar Arguments ..
8 INTEGER INFO, K, LDA, M, N
9 * ..
10 * .. Array Arguments ..
11 COMPLEX A( LDA, * ), TAU( * ), WORK( * )
12 * ..
13 *
14 * Purpose
15 * =======
16 *
17 * CUNG2R generates an m by n complex matrix Q with orthonormal columns,
18 * which is defined as the first n columns of a product of k elementary
19 * reflectors of order m
20 *
21 * Q = H(1) H(2) . . . H(k)
22 *
23 * as returned by CGEQRF.
24 *
25 * Arguments
26 * =========
27 *
28 * M (input) INTEGER
29 * The number of rows of the matrix Q. M >= 0.
30 *
31 * N (input) INTEGER
32 * The number of columns of the matrix Q. M >= N >= 0.
33 *
34 * K (input) INTEGER
35 * The number of elementary reflectors whose product defines the
36 * matrix Q. N >= K >= 0.
37 *
38 * A (input/output) COMPLEX array, dimension (LDA,N)
39 * On entry, the i-th column must contain the vector which
40 * defines the elementary reflector H(i), for i = 1,2,...,k, as
41 * returned by CGEQRF in the first k columns of its array
42 * argument A.
43 * On exit, the m by n matrix Q.
44 *
45 * LDA (input) INTEGER
46 * The first dimension of the array A. LDA >= max(1,M).
47 *
48 * TAU (input) COMPLEX array, dimension (K)
49 * TAU(i) must contain the scalar factor of the elementary
50 * reflector H(i), as returned by CGEQRF.
51 *
52 * WORK (workspace) COMPLEX array, dimension (N)
53 *
54 * INFO (output) INTEGER
55 * = 0: successful exit
56 * < 0: if INFO = -i, the i-th argument has an illegal value
57 *
58 * =====================================================================
59 *
60 * .. Parameters ..
61 COMPLEX ONE, ZERO
62 PARAMETER ( ONE = ( 1.0E+0, 0.0E+0 ),
63 $ ZERO = ( 0.0E+0, 0.0E+0 ) )
64 * ..
65 * .. Local Scalars ..
66 INTEGER I, J, L
67 * ..
68 * .. External Subroutines ..
69 EXTERNAL CLARF, CSCAL, XERBLA
70 * ..
71 * .. Intrinsic Functions ..
72 INTRINSIC MAX
73 * ..
74 * .. Executable Statements ..
75 *
76 * Test the input arguments
77 *
78 INFO = 0
79 IF( M.LT.0 ) THEN
80 INFO = -1
81 ELSE IF( N.LT.0 .OR. N.GT.M ) THEN
82 INFO = -2
83 ELSE IF( K.LT.0 .OR. K.GT.N ) THEN
84 INFO = -3
85 ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
86 INFO = -5
87 END IF
88 IF( INFO.NE.0 ) THEN
89 CALL XERBLA( 'CUNG2R', -INFO )
90 RETURN
91 END IF
92 *
93 * Quick return if possible
94 *
95 IF( N.LE.0 )
96 $ RETURN
97 *
98 * Initialise columns k+1:n to columns of the unit matrix
99 *
100 DO 20 J = K + 1, N
101 DO 10 L = 1, M
102 A( L, J ) = ZERO
103 10 CONTINUE
104 A( J, J ) = ONE
105 20 CONTINUE
106 *
107 DO 40 I = K, 1, -1
108 *
109 * Apply H(i) to A(i:m,i:n) from the left
110 *
111 IF( I.LT.N ) THEN
112 A( I, I ) = ONE
113 CALL CLARF( 'Left', M-I+1, N-I, A( I, I ), 1, TAU( I ),
114 $ A( I, I+1 ), LDA, WORK )
115 END IF
116 IF( I.LT.M )
117 $ CALL CSCAL( M-I, -TAU( I ), A( I+1, I ), 1 )
118 A( I, I ) = ONE - TAU( I )
119 *
120 * Set A(1:i-1,i) to zero
121 *
122 DO 30 L = 1, I - 1
123 A( L, I ) = ZERO
124 30 CONTINUE
125 40 CONTINUE
126 RETURN
127 *
128 * End of CUNG2R
129 *
130 END