[Unicon-group] Another garbage collection curiousity - coexp and static region

[DAVID G. <dav...@ro...>]

Steve's finding reminded me of a problem I'd had a
long time back.  The result was hard to explain.  It's
not necessarily problem, just that the memory usage
was a bit unexpected. The interaction with the string
memory problem just brought it to light. 

The same program that pathologically beat up on the
string area, also used coexpressions.  This caused
Icon to report on collections in the static area.  I
think it might have been Ralph Griswold who clarified
that the numbers were a phantom and it really wasn't
collecting that region. 

The problem was caused because I was using
coexpressions and a lot of them.  (It was pre-unicon
and I needed something that maintained a state but
there was nothing lighter available). 

I recall that coexpressions save the entire state of
the local procedure which can be quite wasteful.  The
sample code and results show the effect. 

The solution was to wrap the cooexpression in a
minimal procedure.  

There followed a discussion with some other folks on
the about a lighter weight construct that had been
experimented with (or abandoned) earlier.  Of course,
an object would probably do handily now, but this was
Icon.

I cobbled together a few lines (below) to see if GC
behaves the same way.  It appears that it does.

I also recall that at some point the regions try and
expand, but it looks like I'm nowhere near that point.

So if those static region statistics are phantoms, I
wonder what they are counting?

David


# -- The results --

coexp-gc thin 1000 1000
collections :  38 38 0 0 
storage:       - 0 12 144 
regions:       - 0 7371325 7371325 

coexp-gc fat 1000 1000
collections :  38 38 0 0 
storage:       - 0 1011 152 
regions:       - 0 7371325 7371325 

coexp-gc fat 10000 10000
collections :  390 384 6 0 
storage:       - 0 10013 152 
regions:       - 0 7371325 7371325 

coexp-gc fat 20000 20000
collections :  796 769 27 0 
storage:       - 0 20013 152 
regions:       - 0 7371325 7371325 

coexp-gc fat 20000 100000
collections :  1453 769 684 0 
storage:       - 0 100014 152 
regions:       - 0 7371325 7371325 

coexp-gc fat 20000 500000
collections :  18850 769 18081 0 
storage:       - 0 500014 152 
regions:       - 0 7371325 7371325 

coexp-gc fat 10000 20000
collections :  411 384 27 0 
storage:       - 0 20013 152 
regions:       - 0 7371325 7371325 

coexp-gc fat 50000 20000
collections :  1950 1923 27 0 
storage:       - 0 20013 152 
regions:       - 0 7371325 7371325 

coexp-gc fat 100000 20000
collections :  3873 3846 27 0 
storage:       - 0 20014 152 
regions:       - 0 7371325 7371325 

coexp-gc fat 500000 20000
collections :  19257 19230 27 0 
storage:       - 0 20014 152 
regions:       - 0 7371325 7371325 

coexp-gc thin 500000 20000
collections :  19230 19230 0 0 
storage:       - 0 15 144 
regions:       - 0 7371325 7371325 


# -- The code --

procedure main(arglist)

if *arglist ~= 3 then usage("Wrong number of
arguments.")

case wt := get(arglist) of {
"fat": gcp := fatgcp
default: gcp := thingcp
}

n := integer(get(arglist)) | usage("itterations")
w := integer(get(arglist)) | usage("words-of-fat")
write("coexp-gc ",wt," ",n," ",w)

cx := gcp(w) 
every 1 to n do ^cx

#every collect(1 to 3)
every writes("collections : "|&collections)  do
writes(" ") ; write()
every writes("storage:      "|"-"|&storage)  do
writes(" ") ; write()
every writes("regions:      "|"-"|&regions)  do
writes(" ") ; write()
write()

end

procedure usage(s)
stop("usage:  coexp-gc [fat|*] <iterations>
<words-of-fat>" || if \s then "\n***"||s else "")
end 

procedure fatgcp(n)
local fat
#fat := list(n)
fat := ""
every 1 to n do fat ||:= ?string(&ascii)
return create n
end

procedure thingcp(n)
return create n
end
############