ctrmm.f

贝尔实验室多年开发的矩阵计算程序库的说明文件

      SUBROUTINE CTRMM(SIDE,UPLO,TRANSA,DIAG,M,N,ALPHA,A,LDA,B,LDB)
*     .. Scalar Arguments ..
      COMPLEX ALPHA
      INTEGER LDA,LDB,M,N
      CHARACTER DIAG,SIDE,TRANSA,UPLO
*     ..
*     .. Array Arguments ..
      COMPLEX A(LDA,*),B(LDB,*)
*     ..
*
*  Purpose
*  =======
*
*  CTRMM  performs one of the matrix-matrix operations
*
*     B := alpha*op( A )*B,   or   B := alpha*B*op( A )
*
*  where  alpha  is a scalar,  B  is an m by n matrix,  A  is a unit, or
*  non-unit,  upper or lower triangular matrix  and  op( A )  is one  of
*
*     op( A ) = A   or   op( A ) = A'   or   op( A ) = conjg( A' ).
*
*  Arguments
*  ==========
*
*  SIDE   - CHARACTER*1.
*           On entry,  SIDE specifies whether  op( A ) multiplies B from
*           the left or right as follows:
*
*              SIDE = 'L' or 'l'   B := alpha*op( A )*B.
*
*              SIDE = 'R' or 'r'   B := alpha*B*op( A ).
*
*           Unchanged on exit.
*
*  UPLO   - CHARACTER*1.
*           On entry, UPLO specifies whether the matrix A is an upper or
*           lower triangular matrix as follows:
*
*              UPLO = 'U' or 'u'   A is an upper triangular matrix.
*
*              UPLO = 'L' or 'l'   A is a lower triangular matrix.
*
*           Unchanged on exit.
*
*  TRANSA - CHARACTER*1.
*           On entry, TRANSA specifies the form of op( A ) to be used in
*           the matrix multiplication as follows:
*
*              TRANSA = 'N' or 'n'   op( A ) = A.
*
*              TRANSA = 'T' or 't'   op( A ) = A'.
*
*              TRANSA = 'C' or 'c'   op( A ) = conjg( A' ).
*
*           Unchanged on exit.
*
*  DIAG   - CHARACTER*1.
*           On entry, DIAG specifies whether or not A is unit triangular
*           as follows:
*
*              DIAG = 'U' or 'u'   A is assumed to be unit triangular.
*
*              DIAG = 'N' or 'n'   A is not assumed to be unit
*                                  triangular.
*
*           Unchanged on exit.
*
*  M      - INTEGER.
*           On entry, M specifies the number of rows of B. M must be at
*           least zero.
*           Unchanged on exit.
*
*  N      - INTEGER.
*           On entry, N specifies the number of columns of B.  N must be
*           at least zero.
*           Unchanged on exit.
*
*  ALPHA  - COMPLEX         .
*           On entry,  ALPHA specifies the scalar  alpha. When  alpha is
*           zero then  A is not referenced and  B need not be set before
*           entry.
*           Unchanged on exit.
*
*  A      - COMPLEX          array of DIMENSION ( LDA, k ), where k is m
*           when  SIDE = 'L' or 'l'  and is  n  when  SIDE = 'R' or 'r'.
*           Before entry  with  UPLO = 'U' or 'u',  the  leading  k by k
*           upper triangular part of the array  A must contain the upper
*           triangular matrix  and the strictly lower triangular part of
*           A is not referenced.
*           Before entry  with  UPLO = 'L' or 'l',  the  leading  k by k
*           lower triangular part of the array  A must contain the lower
*           triangular matrix  and the strictly upper triangular part of
*           A is not referenced.
*           Note that when  DIAG = 'U' or 'u',  the diagonal elements of
*           A  are not referenced either,  but are assumed to be  unity.
*           Unchanged on exit.
*
*  LDA    - INTEGER.
*           On entry, LDA specifies the first dimension of A as declared
*           in the calling (sub) program.  When  SIDE = 'L' or 'l'  then
*           LDA  must be at least  max( 1, m ),  when  SIDE = 'R' or 'r'
*           then LDA must be at least max( 1, n ).
*           Unchanged on exit.
*
*  B      - COMPLEX          array of DIMENSION ( LDB, n ).
*           Before entry,  the leading  m by n part of the array  B must
*           contain the matrix  B,  and  on exit  is overwritten  by the
*           transformed matrix.
*
*  LDB    - INTEGER.
*           On entry, LDB specifies the first dimension of B as declared
*           in  the  calling  (sub)  program.   LDB  must  be  at  least
*           max( 1, m ).
*           Unchanged on exit.
*
*
*  Level 3 Blas routine.
*
*  -- Written on 8-February-1989.
*     Jack Dongarra, Argonne National Laboratory.
*     Iain Duff, AERE Harwell.
*     Jeremy Du Croz, Numerical Algorithms Group Ltd.
*     Sven Hammarling, Numerical Algorithms Group Ltd.
*
*
*     .. External Functions ..
      LOGICAL LSAME
      EXTERNAL LSAME
*     ..
*     .. External Subroutines ..
      EXTERNAL XERBLA
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC CONJG,MAX
*     ..
*     .. Local Scalars ..
      COMPLEX TEMP
      INTEGER I,INFO,J,K,NROWA
      LOGICAL LSIDE,NOCONJ,NOUNIT,UPPER
*     ..
*     .. Parameters ..
      COMPLEX ONE
      PARAMETER (ONE= (1.0E+0,0.0E+0))
      COMPLEX ZERO
      PARAMETER (ZERO= (0.0E+0,0.0E+0))
*     ..
*
*     Test the input parameters.
*
      LSIDE = LSAME(SIDE,'L')
      IF (LSIDE) THEN
          NROWA = M
      ELSE
          NROWA = N
      END IF
      NOCONJ = LSAME(TRANSA,'T')
      NOUNIT = LSAME(DIAG,'N')
      UPPER = LSAME(UPLO,'U')
*
      INFO = 0
      IF ((.NOT.LSIDE) .AND. (.NOT.LSAME(SIDE,'R'))) THEN
          INFO = 1
      ELSE IF ((.NOT.UPPER) .AND. (.NOT.LSAME(UPLO,'L'))) THEN
          INFO = 2
      ELSE IF ((.NOT.LSAME(TRANSA,'N')) .AND.
     +         (.NOT.LSAME(TRANSA,'T')) .AND.
     +         (.NOT.LSAME(TRANSA,'C'))) THEN
          INFO = 3
      ELSE IF ((.NOT.LSAME(DIAG,'U')) .AND. (.NOT.LSAME(DIAG,'N'))) THEN
          INFO = 4
      ELSE IF (M.LT.0) THEN
          INFO = 5
      ELSE IF (N.LT.0) THEN
          INFO = 6
      ELSE IF (LDA.LT.MAX(1,NROWA)) THEN
          INFO = 9
      ELSE IF (LDB.LT.MAX(1,M)) THEN
          INFO = 11
      END IF
      IF (INFO.NE.0) THEN
          CALL XERBLA('CTRMM ',INFO)
          RETURN
      END IF
*
*     Quick return if possible.
*
      IF (M.EQ.0 .OR. N.EQ.0) RETURN
*
*     And when  alpha.eq.zero.
*
      IF (ALPHA.EQ.ZERO) THEN
          DO 20 J = 1,N
              DO 10 I = 1,M
                  B(I,J) = ZERO
   10         CONTINUE
   20     CONTINUE
          RETURN
      END IF
*
*     Start the operations.
*
      IF (LSIDE) THEN
          IF (LSAME(TRANSA,'N')) THEN
*
*           Form  B := alpha*A*B.
*
              IF (UPPER) THEN
                  DO 50 J = 1,N
                      DO 40 K = 1,M
                          IF (B(K,J).NE.ZERO) THEN
                              TEMP = ALPHA*B(K,J)
                              DO 30 I = 1,K - 1
                                  B(I,J) = B(I,J) + TEMP*A(I,K)
   30                         CONTINUE
                              IF (NOUNIT) TEMP = TEMP*A(K,K)
                              B(K,J) = TEMP
                          END IF
   40                 CONTINUE
   50             CONTINUE
              ELSE
                  DO 80 J = 1,N
                      DO 70 K = M,1,-1
                          IF (B(K,J).NE.ZERO) THEN
                              TEMP = ALPHA*B(K,J)
                              B(K,J) = TEMP
                              IF (NOUNIT) B(K,J) = B(K,J)*A(K,K)
                              DO 60 I = K + 1,M
                                  B(I,J) = B(I,J) + TEMP*A(I,K)
   60                         CONTINUE
                          END IF
   70                 CONTINUE
   80             CONTINUE
              END IF
          ELSE
*
*           Form  B := alpha*A'*B   or   B := alpha*conjg( A' )*B.
*
              IF (UPPER) THEN
                  DO 120 J = 1,N
                      DO 110 I = M,1,-1
                          TEMP = B(I,J)
                          IF (NOCONJ) THEN
                              IF (NOUNIT) TEMP = TEMP*A(I,I)
                              DO 90 K = 1,I - 1
                                  TEMP = TEMP + A(K,I)*B(K,J)
   90                         CONTINUE
                          ELSE
                              IF (NOUNIT) TEMP = TEMP*CONJG(A(I,I))
                              DO 100 K = 1,I - 1
                                  TEMP = TEMP + CONJG(A(K,I))*B(K,J)
  100                         CONTINUE
                          END IF
                          B(I,J) = ALPHA*TEMP
  110                 CONTINUE
  120             CONTINUE
              ELSE
                  DO 160 J = 1,N
                      DO 150 I = 1,M
                          TEMP = B(I,J)
                          IF (NOCONJ) THEN
                              IF (NOUNIT) TEMP = TEMP*A(I,I)
                              DO 130 K = I + 1,M
                                  TEMP = TEMP + A(K,I)*B(K,J)
  130                         CONTINUE
                          ELSE
                              IF (NOUNIT) TEMP = TEMP*CONJG(A(I,I))
                              DO 140 K = I + 1,M
                                  TEMP = TEMP + CONJG(A(K,I))*B(K,J)
  140                         CONTINUE
                          END IF
                          B(I,J) = ALPHA*TEMP
  150                 CONTINUE
  160             CONTINUE
              END IF
          END IF
      ELSE
          IF (LSAME(TRANSA,'N')) THEN
*
*           Form  B := alpha*B*A.
*
              IF (UPPER) THEN
                  DO 200 J = N,1,-1
                      TEMP = ALPHA
                      IF (NOUNIT) TEMP = TEMP*A(J,J)
                      DO 170 I = 1,M
                          B(I,J) = TEMP*B(I,J)
  170                 CONTINUE
                      DO 190 K = 1,J - 1
                          IF (A(K,J).NE.ZERO) THEN
                              TEMP = ALPHA*A(K,J)
                              DO 180 I = 1,M
                                  B(I,J) = B(I,J) + TEMP*B(I,K)
  180                         CONTINUE
                          END IF
  190                 CONTINUE
  200             CONTINUE
              ELSE
                  DO 240 J = 1,N
                      TEMP = ALPHA
                      IF (NOUNIT) TEMP = TEMP*A(J,J)
                      DO 210 I = 1,M
                          B(I,J) = TEMP*B(I,J)
  210                 CONTINUE
                      DO 230 K = J + 1,N
                          IF (A(K,J).NE.ZERO) THEN
                              TEMP = ALPHA*A(K,J)
                              DO 220 I = 1,M
                                  B(I,J) = B(I,J) + TEMP*B(I,K)
  220                         CONTINUE
                          END IF
  230                 CONTINUE
  240             CONTINUE
              END IF
          ELSE
*
*           Form  B := alpha*B*A'   or   B := alpha*B*conjg( A' ).
*
              IF (UPPER) THEN
                  DO 280 K = 1,N
                      DO 260 J = 1,K - 1
                          IF (A(J,K).NE.ZERO) THEN
                              IF (NOCONJ) THEN
                                  TEMP = ALPHA*A(J,K)
                              ELSE
                                  TEMP = ALPHA*CONJG(A(J,K))
                              END IF
                              DO 250 I = 1,M
                                  B(I,J) = B(I,J) + TEMP*B(I,K)
  250                         CONTINUE
                          END IF
  260                 CONTINUE
                      TEMP = ALPHA
                      IF (NOUNIT) THEN
                          IF (NOCONJ) THEN
                              TEMP = TEMP*A(K,K)
                          ELSE
                              TEMP = TEMP*CONJG(A(K,K))
                          END IF
                      END IF
                      IF (TEMP.NE.ONE) THEN
                          DO 270 I = 1,M
                              B(I,K) = TEMP*B(I,K)
  270                     CONTINUE
                      END IF
  280             CONTINUE
              ELSE
                  DO 320 K = N,1,-1
                      DO 300 J = K + 1,N
                          IF (A(J,K).NE.ZERO) THEN
                              IF (NOCONJ) THEN
                                  TEMP = ALPHA*A(J,K)
                              ELSE
                                  TEMP = ALPHA*CONJG(A(J,K))
                              END IF
                              DO 290 I = 1,M
                                  B(I,J) = B(I,J) + TEMP*B(I,K)
  290                         CONTINUE
                          END IF
  300                 CONTINUE
                      TEMP = ALPHA
                      IF (NOUNIT) THEN
                          IF (NOCONJ) THEN
                              TEMP = TEMP*A(K,K)
                          ELSE
                              TEMP = TEMP*CONJG(A(K,K))
                          END IF
                      END IF
                      IF (TEMP.NE.ONE) THEN
                          DO 310 I = 1,M
                              B(I,K) = TEMP*B(I,K)
  310                     CONTINUE
                      END IF
  320             CONTINUE
              END IF
          END IF
      END IF
*
      RETURN
*
*     End of CTRMM .
*
      END