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    1:       SUBROUTINE ZGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO )
    2: *
    3: *  -- LAPACK driver routine (version 3.2) --
    4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
    5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
    6: *     November 2006
    7: *
    8: *     .. Scalar Arguments ..
    9:       INTEGER            INFO, LDA, LDB, N, NRHS
   10: *     ..
   11: *     .. Array Arguments ..
   12:       INTEGER            IPIV( * )
   13:       COMPLEX*16         A( LDA, * ), B( LDB, * )
   14: *     ..
   15: *
   16: *  Purpose
   17: *  =======
   18: *
   19: *  ZGESV computes the solution to a complex system of linear equations
   20: *     A * X = B,
   21: *  where A is an N-by-N matrix and X and B are N-by-NRHS matrices.
   22: *
   23: *  The LU decomposition with partial pivoting and row interchanges is
   24: *  used to factor A as
   25: *     A = P * L * U,
   26: *  where P is a permutation matrix, L is unit lower triangular, and U is
   27: *  upper triangular.  The factored form of A is then used to solve the
   28: *  system of equations A * X = B.
   29: *
   30: *  Arguments
   31: *  =========
   32: *
   33: *  N       (input) INTEGER
   34: *          The number of linear equations, i.e., the order of the
   35: *          matrix A.  N >= 0.
   36: *
   37: *  NRHS    (input) INTEGER
   38: *          The number of right hand sides, i.e., the number of columns
   39: *          of the matrix B.  NRHS >= 0.
   40: *
   41: *  A       (input/output) COMPLEX*16 array, dimension (LDA,N)
   42: *          On entry, the N-by-N coefficient matrix A.
   43: *          On exit, the factors L and U from the factorization
   44: *          A = P*L*U; the unit diagonal elements of L are not stored.
   45: *
   46: *  LDA     (input) INTEGER
   47: *          The leading dimension of the array A.  LDA >= max(1,N).
   48: *
   49: *  IPIV    (output) INTEGER array, dimension (N)
   50: *          The pivot indices that define the permutation matrix P;
   51: *          row i of the matrix was interchanged with row IPIV(i).
   52: *
   53: *  B       (input/output) COMPLEX*16 array, dimension (LDB,NRHS)
   54: *          On entry, the N-by-NRHS matrix of right hand side matrix B.
   55: *          On exit, if INFO = 0, the N-by-NRHS solution matrix X.
   56: *
   57: *  LDB     (input) INTEGER
   58: *          The leading dimension of the array B.  LDB >= max(1,N).
   59: *
   60: *  INFO    (output) INTEGER
   61: *          = 0:  successful exit
   62: *          < 0:  if INFO = -i, the i-th argument had an illegal value
   63: *          > 0:  if INFO = i, U(i,i) is exactly zero.  The factorization
   64: *                has been completed, but the factor U is exactly
   65: *                singular, so the solution could not be computed.
   66: *
   67: *  =====================================================================
   68: *
   69: *     .. External Subroutines ..
   70:       EXTERNAL           XERBLA, ZGETRF, ZGETRS
   71: *     ..
   72: *     .. Intrinsic Functions ..
   73:       INTRINSIC          MAX
   74: *     ..
   75: *     .. Executable Statements ..
   76: *
   77: *     Test the input parameters.
   78: *
   79:       INFO = 0
   80:       IF( N.LT.0 ) THEN
   81:          INFO = -1
   82:       ELSE IF( NRHS.LT.0 ) THEN
   83:          INFO = -2
   84:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
   85:          INFO = -4
   86:       ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
   87:          INFO = -7
   88:       END IF
   89:       IF( INFO.NE.0 ) THEN
   90:          CALL XERBLA( 'ZGESV ', -INFO )
   91:          RETURN
   92:       END IF
   93: *
   94: *     Compute the LU factorization of A.
   95: *
   96:       CALL ZGETRF( N, N, A, LDA, IPIV, INFO )
   97:       IF( INFO.EQ.0 ) THEN
   98: *
   99: *        Solve the system A*X = B, overwriting B with X.
  100: *
  101:          CALL ZGETRS( 'No transpose', N, NRHS, A, LDA, IPIV, B, LDB,
  102:      $                INFO )
  103:       END IF
  104:       RETURN
  105: *
  106: *     End of ZGESV
  107: *
  108:       END