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Annotation of rpl/lapack/lapack/zgesv.f, revision 1.1

1.1     ! bertrand    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