subroutine ztrsm ( side, uplo, transa, diag, m, n, alpha, a, lda,
     $                   b, ldb )
*     .. scalar arguments ..
      character*1        side, uplo, transa, diag
      integer            m, n, lda, ldb
      complex*16         alpha
*     .. array arguments ..
      complex*16         a( lda, * ), b( ldb, * )
*     ..
*
*  purpose
*  =======
*
*  ztrsm  solves one of the matrix equations
*
*     op( a )*x = alpha*b,   or   x*op( a ) = alpha*b,
*
*  where alpha is a scalar, x and b are m by n matrices, 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' ).
*
*  the matrix x is overwritten on b.
*
*  parameters
*  ==========
*
*  side   - character*1.
*           on entry, side specifies whether op( a ) appears on the left
*           or right of x as follows:
*
*              side = 'l' or 'l'   op( a )*x = alpha*b.
*
*              side = 'r' or 'r'   x*op( a ) = alpha*b.
*
*           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*16      .
*           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*16       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*16       array of dimension ( ldb, n ).
*           before entry,  the leading  m by n part of the array  b must
*           contain  the  right-hand  side  matrix  b,  and  on exit  is
*           overwritten by the solution matrix  x.
*
*  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.
*