LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ ssyswapr()

subroutine ssyswapr ( character  UPLO,
integer  N,
real, dimension( lda, n )  A,
integer  LDA,
integer  I1,
integer  I2 
)

SSYSWAPR applies an elementary permutation on the rows and columns of a symmetric matrix.

Download SSYSWAPR + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 SSYSWAPR applies an elementary permutation on the rows and the columns of
 a symmetric matrix.
Parameters
[in]UPLO
          UPLO is CHARACTER*1
          Specifies whether the details of the factorization are stored
          as an upper or lower triangular matrix.
          = 'U':  Upper triangular, form is A = U*D*U**T;
          = 'L':  Lower triangular, form is A = L*D*L**T.
[in]N
          N is INTEGER
          The order of the matrix A.  N >= 0.
[in,out]A
          A is REAL array, dimension (LDA,N)
          On entry, the NB diagonal matrix D and the multipliers
          used to obtain the factor U or L as computed by SSYTRF.

          On exit, if INFO = 0, the (symmetric) inverse of the original
          matrix.  If UPLO = 'U', the upper triangular part of the
          inverse is formed and the part of A below the diagonal is not
          referenced; if UPLO = 'L' the lower triangular part of the
          inverse is formed and the part of A above the diagonal is
          not referenced.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A.  LDA >= max(1,N).
[in]I1
          I1 is INTEGER
          Index of the first row to swap
[in]I2
          I2 is INTEGER
          Index of the second row to swap
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 101 of file ssyswapr.f.

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  REAL A( LDA, N )
113 *
114 * =====================================================================
115 *
116 * ..
117 * .. Local Scalars ..
118  LOGICAL UPPER
119  INTEGER I
120  REAL TMP
121 *
122 * .. External Functions ..
123  LOGICAL LSAME
124  EXTERNAL lsame
125 * ..
126 * .. External Subroutines ..
127  EXTERNAL sswap
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 sswap( 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 sswap( 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
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
subroutine sswap(N, SX, INCX, SY, INCY)
SSWAP
Definition: sswap.f:82
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