LAPACK  3.6.1 LAPACK: Linear Algebra PACKage
cheswapr.f
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1 *> \brief \b CHESWAPR applies an elementary permutation on the rows and columns of a Hermitian matrix.
2 *
3 * =========== DOCUMENTATION ===========
4 *
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17 *
18 * Definition:
19 * ===========
20 *
21 * SUBROUTINE CHESWAPR( UPLO, N, A, LDA, I1, I2)
22 *
23 * .. Scalar Arguments ..
24 * CHARACTER UPLO
25 * INTEGER I1, I2, LDA, N
26 * ..
27 * .. Array Arguments ..
28 * COMPLEX A( LDA, N )
29 *
30 *
31 *> \par Purpose:
32 * =============
33 *>
34 *> \verbatim
35 *>
36 *> CHESWAPR applies an elementary permutation on the rows and the columns of
37 *> a hermitian matrix.
38 *> \endverbatim
39 *
40 * Arguments:
41 * ==========
42 *
43 *> \param[in] UPLO
44 *> \verbatim
45 *> UPLO is CHARACTER*1
46 *> Specifies whether the details of the factorization are stored
47 *> as an upper or lower triangular matrix.
48 *> = 'U': Upper triangular, form is A = U*D*U**T;
49 *> = 'L': Lower triangular, form is A = L*D*L**T.
50 *> \endverbatim
51 *>
52 *> \param[in] N
53 *> \verbatim
54 *> N is INTEGER
55 *> The order of the matrix A. N >= 0.
56 *> \endverbatim
57 *>
58 *> \param[in,out] A
59 *> \verbatim
60 *> A is COMPLEX array, dimension (LDA,N)
61 *> On entry, the NB diagonal matrix D and the multipliers
62 *> used to obtain the factor U or L as computed by CSYTRF.
63 *>
64 *> On exit, if INFO = 0, the (symmetric) inverse of the original
65 *> matrix. If UPLO = 'U', the upper triangular part of the
66 *> inverse is formed and the part of A below the diagonal is not
67 *> referenced; if UPLO = 'L' the lower triangular part of the
68 *> inverse is formed and the part of A above the diagonal is
69 *> not referenced.
70 *> \endverbatim
71 *>
72 *> \param[in] LDA
73 *> \verbatim
74 *> LDA is INTEGER
75 *> The leading dimension of the array A. LDA >= max(1,N).
76 *> \endverbatim
77 *>
78 *> \param[in] I1
79 *> \verbatim
80 *> I1 is INTEGER
81 *> Index of the first row to swap
82 *> \endverbatim
83 *>
84 *> \param[in] I2
85 *> \verbatim
86 *> I2 is INTEGER
87 *> Index of the second row to swap
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 September 2012
99 *
100 *> \ingroup complexHEauxiliary
101 *
102 * =====================================================================
103  SUBROUTINE cheswapr( UPLO, N, A, LDA, I1, I2)
104 *
105 * -- LAPACK auxiliary routine (version 3.4.2) --
106 * -- LAPACK is a software package provided by Univ. of Tennessee, --
107 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
108 * September 2012
109 *
110 * .. Scalar Arguments ..
111  CHARACTER UPLO
112  INTEGER I1, I2, LDA, N
113 * ..
114 * .. Array Arguments ..
115  COMPLEX A( lda, n )
116 *
117 * =====================================================================
118 *
119 * ..
120 * .. Local Scalars ..
121  LOGICAL UPPER
122  INTEGER I
123  COMPLEX TMP
124 *
125 * .. External Functions ..
126  LOGICAL LSAME
127  EXTERNAL lsame
128 * ..
129 * .. External Subroutines ..
130  EXTERNAL cswap
131 * ..
132 * .. Executable Statements ..
133 *
134  upper = lsame( uplo, 'U' )
135  IF (upper) THEN
136 *
137 * UPPER
138 * first swap
139 * - swap column I1 and I2 from I1 to I1-1
140  CALL cswap( i1-1, a(1,i1), 1, a(1,i2), 1 )
141 *
142 * second swap :
143 * - swap A(I1,I1) and A(I2,I2)
144 * - swap row I1 from I1+1 to I2-1 with col I2 from I1+1 to I2-1
145 * - swap A(I2,I1) and A(I1,I2)
146
147  tmp=a(i1,i1)
148  a(i1,i1)=a(i2,i2)
149  a(i2,i2)=tmp
150 *
151  DO i=1,i2-i1-1
152  tmp=a(i1,i1+i)
153  a(i1,i1+i)=conjg(a(i1+i,i2))
154  a(i1+i,i2)=conjg(tmp)
155  END DO
156 *
157  a(i1,i2)=conjg(a(i1,i2))
158
159 *
160 * third swap
161 * - swap row I1 and I2 from I2+1 to N
162  DO i=i2+1,n
163  tmp=a(i1,i)
164  a(i1,i)=a(i2,i)
165  a(i2,i)=tmp
166  END DO
167 *
168  ELSE
169 *
170 * LOWER
171 * first swap
172 * - swap row I1 and I2 from 1 to I1-1
173  CALL cswap ( i1-1, a(i1,1), lda, a(i2,1), lda )
174 *
175 * second swap :
176 * - swap A(I1,I1) and A(I2,I2)
177 * - swap col I1 from I1+1 to I2-1 with row I2 from I1+1 to I2-1
178 * - swap A(I2,I1) and A(I1,I2)
179
180  tmp=a(i1,i1)
181  a(i1,i1)=a(i2,i2)
182  a(i2,i2)=tmp
183 *
184  DO i=1,i2-i1-1
185  tmp=a(i1+i,i1)
186  a(i1+i,i1)=conjg(a(i2,i1+i))
187  a(i2,i1+i)=conjg(tmp)
188  END DO
189 *
190  a(i2,i1)=conjg(a(i2,i1))
191 *
192 * third swap
193 * - swap col I1 and I2 from I2+1 to N
194  DO i=i2+1,n
195  tmp=a(i,i1)
196  a(i,i1)=a(i,i2)
197  a(i,i2)=tmp
198  END DO
199 *
200  ENDIF
201
202  END SUBROUTINE cheswapr
203
subroutine cswap(N, CX, INCX, CY, INCY)
CSWAP
Definition: cswap.f:52
subroutine cheswapr(UPLO, N, A, LDA, I1, I2)
CHESWAPR applies an elementary permutation on the rows and columns of a Hermitian matrix...
Definition: cheswapr.f:104