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    1:       SUBROUTINE ZSYSWAPR( UPLO, N, A, LDA, I1, I2)
    2: *
    3: *  -- LAPACK auxiliary routine (version 3.3.1) --
    4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
    5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
    6: *  -- April 2011                                                      --
    7: *
    8: *     .. Scalar Arguments ..
    9:       CHARACTER        UPLO
   10:       INTEGER          I1, I2, LDA, N
   11: *     ..
   12: *     .. Array Arguments ..
   13:       DOUBLE COMPLEX   A( LDA, N )
   14: *
   15: *  Purpose
   16: *  =======
   17: *
   18: *  ZSYSWAPR applies an elementary permutation on the rows and the columns of
   19: *  a symmetric matrix.
   20: *
   21: *  Arguments
   22: *  =========
   23: *
   24: *  UPLO    (input) CHARACTER*1
   25: *          Specifies whether the details of the factorization are stored
   26: *          as an upper or lower triangular matrix.
   27: *          = 'U':  Upper triangular, form is A = U*D*U**T;
   28: *          = 'L':  Lower triangular, form is A = L*D*L**T.
   29: *
   30: *  N       (input) INTEGER
   31: *          The order of the matrix A.  N >= 0.
   32: *
   33: *  A       (input/output) DOUBLE COMPLEX array, dimension (LDA,N)
   34: *          On entry, the NB diagonal matrix D and the multipliers
   35: *          used to obtain the factor U or L as computed by ZSYTRF.
   36: *
   37: *          On exit, if INFO = 0, the (symmetric) inverse of the original
   38: *          matrix.  If UPLO = 'U', the upper triangular part of the
   39: *          inverse is formed and the part of A below the diagonal is not
   40: *          referenced; if UPLO = 'L' the lower triangular part of the
   41: *          inverse is formed and the part of A above the diagonal is
   42: *          not referenced.
   43: *
   44: *  LDA     (input) INTEGER
   45: *          The leading dimension of the array A.  LDA >= max(1,N).
   46: *
   47: *  I1      (input) INTEGER
   48: *          Index of the first row to swap
   49: *
   50: *  I2      (input) INTEGER
   51: *          Index of the second row to swap
   52: *
   53: *  =====================================================================
   54: *
   55: *     ..
   56: *     .. Local Scalars ..
   57:       LOGICAL            UPPER
   58:       INTEGER            I
   59:       DOUBLE COMPLEX     TMP
   60: *
   61: *     .. External Functions ..
   62:       LOGICAL            LSAME
   63:       EXTERNAL           LSAME
   64: *     ..
   65: *     .. External Subroutines ..
   66:       EXTERNAL           ZSWAP
   67: *     ..
   68: *     .. Executable Statements ..
   69: *
   70:       UPPER = LSAME( UPLO, 'U' )
   71:       IF (UPPER) THEN
   72: *
   73: *         UPPER
   74: *         first swap
   75: *          - swap column I1 and I2 from I1 to I1-1 
   76:          CALL ZSWAP( I1-1, A(1,I1), 1, A(1,I2), 1 )
   77: *
   78: *          second swap :
   79: *          - swap A(I1,I1) and A(I2,I2)
   80: *          - swap row I1 from I1+1 to I2-1 with col I2 from I1+1 to I2-1     
   81:          TMP=A(I1,I1)
   82:          A(I1,I1)=A(I2,I2)
   83:          A(I2,I2)=TMP
   84: *
   85:          DO I=1,I2-I1-1
   86:             TMP=A(I1,I1+I)
   87:             A(I1,I1+I)=A(I1+I,I2)
   88:             A(I1+I,I2)=TMP
   89:          END DO
   90: *
   91: *          third swap
   92: *          - swap row I1 and I2 from I2+1 to N
   93:          DO I=I2+1,N
   94:             TMP=A(I1,I)
   95:             A(I1,I)=A(I2,I)
   96:             A(I2,I)=TMP
   97:          END DO
   98: *
   99:         ELSE
  100: *
  101: *         LOWER
  102: *         first swap
  103: *          - swap row I1 and I2 from I1 to I1-1 
  104:          CALL ZSWAP( I1-1, A(I1,1), LDA, A(I2,1), LDA )
  105: *
  106: *         second swap :
  107: *          - swap A(I1,I1) and A(I2,I2)
  108: *          - swap col I1 from I1+1 to I2-1 with row I2 from I1+1 to I2-1     
  109:           TMP=A(I1,I1)
  110:           A(I1,I1)=A(I2,I2)
  111:           A(I2,I2)=TMP
  112: *
  113:           DO I=1,I2-I1-1
  114:              TMP=A(I1+I,I1)
  115:              A(I1+I,I1)=A(I2,I1+I)
  116:              A(I2,I1+I)=TMP
  117:           END DO
  118: *
  119: *         third swap
  120: *          - swap col I1 and I2 from I2+1 to N
  121:           DO I=I2+1,N
  122:              TMP=A(I,I1)
  123:              A(I,I1)=A(I,I2)
  124:              A(I,I2)=TMP
  125:           END DO
  126: *
  127:       ENDIF
  128:       END SUBROUTINE ZSYSWAPR
  129: