Return to ztrtrs.f CVS log

Up to [local] / rpl / lapack / lapack

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

1.1     ! bertrand    1:       SUBROUTINE ZTRTRS( UPLO, TRANS, DIAG, N, NRHS, A, LDA, B, LDB,
        !             2:      $                   INFO )
        !             3: *
        !             4: *  -- LAPACK routine (version 3.2) --
        !             5: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
        !             6: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
        !             7: *     November 2006
        !             8: *
        !             9: *     .. Scalar Arguments ..
        !            10:       CHARACTER          DIAG, TRANS, UPLO
        !            11:       INTEGER            INFO, LDA, LDB, N, NRHS
        !            12: *     ..
        !            13: *     .. Array Arguments ..
        !            14:       COMPLEX*16         A( LDA, * ), B( LDB, * )
        !            15: *     ..
        !            16: *
        !            17: *  Purpose
        !            18: *  =======
        !            19: *
        !            20: *  ZTRTRS solves a triangular system of the form
        !            21: *
        !            22: *     A * X = B,  A**T * X = B,  or  A**H * X = B,
        !            23: *
        !            24: *  where A is a triangular matrix of order N, and B is an N-by-NRHS
        !            25: *  matrix.  A check is made to verify that A is nonsingular.
        !            26: *
        !            27: *  Arguments
        !            28: *  =========
        !            29: *
        !            30: *  UPLO    (input) CHARACTER*1
        !            31: *          = 'U':  A is upper triangular;
        !            32: *          = 'L':  A is lower triangular.
        !            33: *
        !            34: *  TRANS   (input) CHARACTER*1
        !            35: *          Specifies the form of the system of equations:
        !            36: *          = 'N':  A * X = B     (No transpose)
        !            37: *          = 'T':  A**T * X = B  (Transpose)
        !            38: *          = 'C':  A**H * X = B  (Conjugate transpose)
        !            39: *
        !            40: *  DIAG    (input) CHARACTER*1
        !            41: *          = 'N':  A is non-unit triangular;
        !            42: *          = 'U':  A is unit triangular.
        !            43: *
        !            44: *  N       (input) INTEGER
        !            45: *          The order of the matrix A.  N >= 0.
        !            46: *
        !            47: *  NRHS    (input) INTEGER
        !            48: *          The number of right hand sides, i.e., the number of columns
        !            49: *          of the matrix B.  NRHS >= 0.
        !            50: *
        !            51: *  A       (input) COMPLEX*16 array, dimension (LDA,N)
        !            52: *          The triangular matrix A.  If UPLO = 'U', the leading N-by-N
        !            53: *          upper triangular part of the array A contains the upper
        !            54: *          triangular matrix, and the strictly lower triangular part of
        !            55: *          A is not referenced.  If UPLO = 'L', the leading N-by-N lower
        !            56: *          triangular part of the array A contains the lower triangular
        !            57: *          matrix, and the strictly upper triangular part of A is not
        !            58: *          referenced.  If DIAG = 'U', the diagonal elements of A are
        !            59: *          also not referenced and are assumed to be 1.
        !            60: *
        !            61: *  LDA     (input) INTEGER
        !            62: *          The leading dimension of the array A.  LDA >= max(1,N).
        !            63: *
        !            64: *  B       (input/output) COMPLEX*16 array, dimension (LDB,NRHS)
        !            65: *          On entry, the right hand side matrix B.
        !            66: *          On exit, if INFO = 0, the solution matrix X.
        !            67: *
        !            68: *  LDB     (input) INTEGER
        !            69: *          The leading dimension of the array B.  LDB >= max(1,N).
        !            70: *
        !            71: *  INFO    (output) INTEGER
        !            72: *          = 0:  successful exit
        !            73: *          < 0: if INFO = -i, the i-th argument had an illegal value
        !            74: *          > 0: if INFO = i, the i-th diagonal element of A is zero,
        !            75: *               indicating that the matrix is singular and the solutions
        !            76: *               X have not been computed.
        !            77: *
        !            78: *  =====================================================================
        !            79: *
        !            80: *     .. Parameters ..
        !            81:       COMPLEX*16         ZERO, ONE
        !            82:       PARAMETER          ( ZERO = ( 0.0D+0, 0.0D+0 ),
        !            83:      $                   ONE = ( 1.0D+0, 0.0D+0 ) )
        !            84: *     ..
        !            85: *     .. Local Scalars ..
        !            86:       LOGICAL            NOUNIT
        !            87: *     ..
        !            88: *     .. External Functions ..
        !            89:       LOGICAL            LSAME
        !            90:       EXTERNAL           LSAME
        !            91: *     ..
        !            92: *     .. External Subroutines ..
        !            93:       EXTERNAL           XERBLA, ZTRSM
        !            94: *     ..
        !            95: *     .. Intrinsic Functions ..
        !            96:       INTRINSIC          MAX
        !            97: *     ..
        !            98: *     .. Executable Statements ..
        !            99: *
        !           100: *     Test the input parameters.
        !           101: *
        !           102:       INFO = 0
        !           103:       NOUNIT = LSAME( DIAG, 'N' )
        !           104:       IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
        !           105:          INFO = -1
        !           106:       ELSE IF( .NOT.LSAME( TRANS, 'N' ) .AND. .NOT.
        !           107:      $         LSAME( TRANS, 'T' ) .AND. .NOT.LSAME( TRANS, 'C' ) ) THEN
        !           108:          INFO = -2
        !           109:       ELSE IF( .NOT.NOUNIT .AND. .NOT.LSAME( DIAG, 'U' ) ) THEN
        !           110:          INFO = -3
        !           111:       ELSE IF( N.LT.0 ) THEN
        !           112:          INFO = -4
        !           113:       ELSE IF( NRHS.LT.0 ) THEN
        !           114:          INFO = -5
        !           115:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
        !           116:          INFO = -7
        !           117:       ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
        !           118:          INFO = -9
        !           119:       END IF
        !           120:       IF( INFO.NE.0 ) THEN
        !           121:          CALL XERBLA( 'ZTRTRS', -INFO )
        !           122:          RETURN
        !           123:       END IF
        !           124: *
        !           125: *     Quick return if possible
        !           126: *
        !           127:       IF( N.EQ.0 )
        !           128:      $   RETURN
        !           129: *
        !           130: *     Check for singularity.
        !           131: *
        !           132:       IF( NOUNIT ) THEN
        !           133:          DO 10 INFO = 1, N
        !           134:             IF( A( INFO, INFO ).EQ.ZERO )
        !           135:      $         RETURN
        !           136:    10    CONTINUE
        !           137:       END IF
        !           138:       INFO = 0
        !           139: *
        !           140: *     Solve A * x = b,  A**T * x = b,  or  A**H * x = b.
        !           141: *
        !           142:       CALL ZTRSM( 'Left', UPLO, TRANS, DIAG, N, NRHS, ONE, A, LDA, B,
        !           143:      $            LDB )
        !           144: *
        !           145:       RETURN
        !           146: *
        !           147: *     End of ZTRTRS
        !           148: *
        !           149:       END