Here is the promised followup with more details on the slow safe
unmarshalling. On
http://www.cs.ru.nl/~tews/nsUnicodeToTeXCMRt1.i.oast you can
download 281 KB of marshalled data. On my machine it takes 23
seconds to check with native code.

The data is of type 

  annotated translationUnit_type = annotated * annotated topForm_type list 

You can test it with the following piece of code:

open Cc_ast_gen_type
open Ast_annotation

let file = "/home/tews/src/elsa/elsa/in/big/nsUnicodeToTeXCMRt1.i.oast"
;;

try
  SafeUnmarshal.from_channel 
    [^ annotated translationUnit_type ^]
    (open_in file);
  print_endline "OK"
with
  | _ -> print_endline "FAIL"


compile with

        ocamlopt.opt safeUnmarshal.cmxa ast_annotation.ml elsa_util.ml \
              ml_ctype.ml cc_ml_types.ml cc_ast_gen_type.ml justunmarshal.ml

The additional files are from Olmar, get them here:

http://www.sos.cs.ru.nl/cgi-bin/~tews/olmar/viewvc-patch.cgi/elsa/elsa/ast_annotation.ml?revision=olmar-release-2006-09-07
http://www.sos.cs.ru.nl/cgi-bin/~tews/olmar/viewvc-patch.cgi/elsa/elsa/elsa_util.ml?revision=olmar-release-2006-09-07
http://www.sos.cs.ru.nl/cgi-bin/~tews/olmar/viewvc-patch.cgi/elsa/elsa/ml_ctype.ml?revision=olmar-release-2006-09-07
http://www.sos.cs.ru.nl/cgi-bin/~tews/olmar/viewvc-patch.cgi/elsa/elsa/cc_ml_types.ml?revision=olmar-release-2006-09-07
http://www.sos.cs.ru.nl/cgi-bin/~tews/olmar/viewvc-patch.cgi/elsa/elsa/cc_ast_gen_type.ml?revision=olmar-release-2006-09-07

To produce graphs like http://www.cs.ru.nl/~tews/marshal-plot.eps
you need to download Olmar, compile it and then
- ./regrtest -ocaml  in subdir elsa
- ./regtest-oast | grep time >data in subdir asttools
- gnuplot plot

where the plot file is something like

reset

set grid
unset mouse
set terminal x11 persist
#set terminal postscript enhanced color

set xlabel "size (Bytes)"
set ylabel "time (s)"
set key left

z = 2.1

plot "data" using 6:3 title "SafeUnmarshal user time", \
	(0.000017088 * x) ** 2.1


Bye,

Hendrik