NAME

     bsp_set_tagsize - tag size of a BSMP packet.



C SYNOPSIS

     #include "bsp.h"

     void bsp_set_tagsize(int *tag_bytes);


FORTRAN SYNOPSIS

     SUBROUTINE  bspsettagsize(tag_bytes)
       INTEGER, intent(INOUT) :: tag_bytes



DESCRIPTION

     Allowing the user to set the tag size  enables  the  use  of
     tags that are appropriate for the communication requirements
     of each superstep.  This should be  particularly  useful  in
     the development of subroutines either in user programs or in
     libraries.

     The procedure must be called collectively by all  processes.
     A  change  in  tag size takes effect in the following super-
     step; it then becomes valid.

     The value of tag_bytes on entry to the procedure,  specifies
     the size of the fixed-length portion of every message in the
     current and succeeding supersteps; the default tag  size  is
     zero.  On return from the procedure, tag_bytes is changed to
     reflect the previous value of the tag size.



SEE ALSO

     bsmp(3)    ,bsp_send(3),    bsp_get_tag(3),    bsp_qsize(3),
     bsp_move(3), bsp_hpmove(3)

     ``BSPlib: The BSP Programming Library'' Jonathan M. D. Hill,
     Bill  McColl,  Dan  C.  Stefanescu,  Mark W. Goudreau, Kevin
     Lang, Satish B. Rao, , Torsten Suel, Thanasis Tsantilas, and
     Rob  Bisseling.  Parallel  Computing,  to  appear  1998. See
     http://www.bsp-worldwide.org for more details.



NOTES

     i    The tag size of outgoing messages is prescribed by  the
          tag size that is valid in the current superstep.


     ii   The tag  size  of  messages  in  the  system  queue  is
          prescribed by the tag size that was valid in the previ-
          ous superstep.

     iii  bsp_set_tagsize(3) must be called by all processes with
          the  same  argument  in  the  same  superstep.  In this
          respect, it is similar to bsp_push_reg(3).


     iv   bsp_set_tagsize(3) takes effect in the next superstep.



     v    Given a sequence of bsp_set_tagsize(3) within the  same
          superstep,  then the value of the last of these will be
          used as the tag size for the next superstep.


     vi   The default tag size is 0.



BUGS

     Problems  and  bug  reports  should  be  mailed  to  bsplib-
     bugs@comlab.ox.ac.uk



AUTHORS

     The Oxford BSP Toolset implementation of BSPlib was  written
     by Jonathan.Hill@comlab.ox.ac.uk
     http://www.comlab.ox.ac.uk/oucl/people/jonathan.hill.html



























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