LAPACK  3.10.0
LAPACK: Linear Algebra PACKage
csyswapr.f
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1 *> \brief \b CSYSWAPR
2 *
3 * =========== DOCUMENTATION ===========
4 *
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
7 *
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15 *> [TXT]</a>
16 *> \endhtmlonly
17 *
18 * Definition:
19 * ===========
20 *
21 * SUBROUTINE CSYSWAPR( 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 *> CSYSWAPR applies an elementary permutation on the rows and the columns of
37 *> a symmetric 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 *> \ingroup complexSYauxiliary
99 *
100 * =====================================================================
101  SUBROUTINE csyswapr( UPLO, N, A, LDA, I1, I2)
102 *
103 * -- LAPACK auxiliary routine --
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 I1, I2, LDA, N
110 * ..
111 * .. Array Arguments ..
112  COMPLEX A( LDA, N )
113 *
114 * =====================================================================
115 *
116 * ..
117 * .. Local Scalars ..
118  LOGICAL UPPER
119  INTEGER I
120  COMPLEX TMP
121 *
122 * .. External Functions ..
123  LOGICAL LSAME
124  EXTERNAL lsame
125 * ..
126 * .. External Subroutines ..
127  EXTERNAL cswap
128 * ..
129 * .. Executable Statements ..
130 *
131  upper = lsame( uplo, 'U' )
132  IF (upper) THEN
133 *
134 * UPPER
135 * first swap
136 * - swap column I1 and I2 from I1 to I1-1
137  CALL cswap( i1-1, a(1,i1), 1, a(1,i2), 1 )
138 *
139 * second swap :
140 * - swap A(I1,I1) and A(I2,I2)
141 * - swap row I1 from I1+1 to I2-1 with col I2 from I1+1 to I2-1
142  tmp=a(i1,i1)
143  a(i1,i1)=a(i2,i2)
144  a(i2,i2)=tmp
145 *
146  DO i=1,i2-i1-1
147  tmp=a(i1,i1+i)
148  a(i1,i1+i)=a(i1+i,i2)
149  a(i1+i,i2)=tmp
150  END DO
151 *
152 * third swap
153 * - swap row I1 and I2 from I2+1 to N
154  DO i=i2+1,n
155  tmp=a(i1,i)
156  a(i1,i)=a(i2,i)
157  a(i2,i)=tmp
158  END DO
159 *
160  ELSE
161 *
162 * LOWER
163 * first swap
164 * - swap row I1 and I2 from I1 to I1-1
165  CALL cswap ( i1-1, a(i1,1), lda, a(i2,1), lda )
166 *
167 * second swap :
168 * - swap A(I1,I1) and A(I2,I2)
169 * - swap col I1 from I1+1 to I2-1 with row I2 from I1+1 to I2-1
170  tmp=a(i1,i1)
171  a(i1,i1)=a(i2,i2)
172  a(i2,i2)=tmp
173 *
174  DO i=1,i2-i1-1
175  tmp=a(i1+i,i1)
176  a(i1+i,i1)=a(i2,i1+i)
177  a(i2,i1+i)=tmp
178  END DO
179 *
180 * third swap
181 * - swap col I1 and I2 from I2+1 to N
182  DO i=i2+1,n
183  tmp=a(i,i1)
184  a(i,i1)=a(i,i2)
185  a(i,i2)=tmp
186  END DO
187 *
188  ENDIF
189  END SUBROUTINE csyswapr
190 
subroutine cswap(N, CX, INCX, CY, INCY)
CSWAP
Definition: cswap.f:81
subroutine csyswapr(UPLO, N, A, LDA, I1, I2)
CSYSWAPR
Definition: csyswapr.f:102