Shared Memory and Scn_assmblr

[jpl284 at cit-vax.ARPA]

From:  Jonathan Leech <jpl284 at cit-vax.ARPA>

	Can anyone tell me if it's possible  for  processes  to  share
memory, and how to do it (on at 4.2 11/780)? The problem I have is  as
follows:

	I am trying to convert Frank  Crow's  scn_assmblr  to  use  an
in-memory frame buffer.  Scn_assmblr  has  a  top-level  process  (the
'task_master')	which  depth-sorts  objects  and  then	creates  other
processes to which it pipes  information  on  rendering  polygons  and
performing other manipulations on the frame buffer.   The  approach  I
am using right now is to create an appropriate size  file  (1  Mbyte),
then  read  and  write	it  in	every	process   that	 is   invoked.
Unfortunately the time required to read and write the file  is	fairly
significant and one goal is to get the	program  running  as  fast  as
possible.

	I would like to allocate the  frame  buffer  memory  and  then
share it among the various processes, but I don't see any  way	to  do
this. Any help would be greatly appreciated.

	Thanks,
	Jon Leech
	jpl284 at cit-vax