LAPACK 3.3.1 Linear Algebra PACKage

# cheswapr.f

Go to the documentation of this file.
```00001       SUBROUTINE CHESWAPR( UPLO, N, A, LDA, I1, I2)
00002 *
00003 *  -- LAPACK auxiliary routine (version 3.3.1) --
00004 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00005 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00006 *  -- April 2011                                                      --
00007 *
00008 *     .. Scalar Arguments ..
00009       CHARACTER        UPLO
00010       INTEGER          I1, I2, LDA, N
00011 *     ..
00012 *     .. Array Arguments ..
00013       COMPLEX          A( LDA, N )
00014 *
00015 *  Purpose
00016 *  =======
00017 *
00018 *  CHESWAPR applies an elementary permutation on the rows and the columns of
00019 *  a hermitian matrix.
00020 *
00021 *  Arguments
00022 *  =========
00023 *
00024 *  UPLO    (input) CHARACTER*1
00025 *          Specifies whether the details of the factorization are stored
00026 *          as an upper or lower triangular matrix.
00027 *          = 'U':  Upper triangular, form is A = U*D*U**T;
00028 *          = 'L':  Lower triangular, form is A = L*D*L**T.
00029 *
00030 *  N       (input) INTEGER
00031 *          The order of the matrix A.  N >= 0.
00032 *
00033 *  A       (input/output) COMPLEX array, dimension (LDA,N)
00034 *          On entry, the NB diagonal matrix D and the multipliers
00035 *          used to obtain the factor U or L as computed by CSYTRF.
00036 *
00037 *          On exit, if INFO = 0, the (symmetric) inverse of the original
00038 *          matrix.  If UPLO = 'U', the upper triangular part of the
00039 *          inverse is formed and the part of A below the diagonal is not
00040 *          referenced; if UPLO = 'L' the lower triangular part of the
00041 *          inverse is formed and the part of A above the diagonal is
00042 *          not referenced.
00043 *
00044 *  LDA     (input) INTEGER
00045 *          The leading dimension of the array A.  LDA >= max(1,N).
00046 *
00047 *  I1      (input) INTEGER
00048 *          Index of the first row to swap
00049 *
00050 *  I2      (input) INTEGER
00051 *          Index of the second row to swap
00052 *
00053 *  =====================================================================
00054 *
00055 *     ..
00056 *     .. Local Scalars ..
00057       LOGICAL            UPPER
00058       INTEGER            I
00059       COMPLEX            TMP
00060 *
00061 *     .. External Functions ..
00062       LOGICAL            LSAME
00063       EXTERNAL           LSAME
00064 *     ..
00065 *     .. External Subroutines ..
00066       EXTERNAL           CSWAP
00067 *     ..
00068 *     .. Executable Statements ..
00069 *
00070       UPPER = LSAME( UPLO, 'U' )
00071       IF (UPPER) THEN
00072 *
00073 *         UPPER
00074 *         first swap
00075 *          - swap column I1 and I2 from I1 to I1-1
00076          CALL CSWAP( I1-1, A(1,I1), 1, A(1,I2), 1 )
00077 *
00078 *          second swap :
00079 *          - swap A(I1,I1) and A(I2,I2)
00080 *          - swap row I1 from I1+1 to I2-1 with col I2 from I1+1 to I2-1
00081 *          - swap A(I2,I1) and A(I1,I2)
00082
00083          TMP=A(I1,I1)
00084          A(I1,I1)=A(I2,I2)
00085          A(I2,I2)=TMP
00086 *
00087          DO I=1,I2-I1-1
00088             TMP=A(I1,I1+I)
00089             A(I1,I1+I)=CONJG(A(I1+I,I2))
00090             A(I1+I,I2)=CONJG(TMP)
00091          END DO
00092 *
00093           A(I1,I2)=CONJG(A(I1,I2))
00094
00095 *
00096 *          third swap
00097 *          - swap row I1 and I2 from I2+1 to N
00098          DO I=I2+1,N
00099             TMP=A(I1,I)
00100             A(I1,I)=A(I2,I)
00101             A(I2,I)=TMP
00102          END DO
00103 *
00104         ELSE
00105 *
00106 *         LOWER
00107 *         first swap
00108 *          - swap row I1 and I2 from 1 to I1-1
00109          CALL CSWAP ( I1-1, A(I1,1), LDA, A(I2,1), LDA )
00110 *
00111 *         second swap :
00112 *          - swap A(I1,I1) and A(I2,I2)
00113 *          - swap col I1 from I1+1 to I2-1 with row I2 from I1+1 to I2-1
00114 *          - swap A(I2,I1) and A(I1,I2)
00115
00116           TMP=A(I1,I1)
00117           A(I1,I1)=A(I2,I2)
00118           A(I2,I2)=TMP
00119 *
00120           DO I=1,I2-I1-1
00121              TMP=A(I1+I,I1)
00122              A(I1+I,I1)=CONJG(A(I2,I1+I))
00123              A(I2,I1+I)=CONJG(TMP)
00124           END DO
00125 *
00126           A(I2,I1)=CONJG(A(I2,I1))
00127 *
00128 *         third swap
00129 *          - swap col I1 and I2 from I2+1 to N
00130           DO I=I2+1,N
00131              TMP=A(I,I1)
00132              A(I,I1)=A(I,I2)
00133              A(I,I2)=TMP
00134           END DO
00135 *
00136       ENDIF
00137
00138       END SUBROUTINE CHESWAPR
00139
```