From: "John Caml" <camljohn42@gmail.com>
To: caml-list@yquem.inria.fr
Subject: large hash tables
Date: Tue, 19 Feb 2008 15:01:46 -0800 [thread overview]
Message-ID: <33d2b3f70802191501v39346a56x4b1852b84d4067b4@mail.gmail.com> (raw)
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I need to load roughly 100 million items into a memory based hash table,
where each key is an integer and each value is an integer and a float. Under
C++ stdlib's map library, this requires 800 MB of memory. Under my naive
porting of my C++ program to Ocaml, only 12 million rows get loaded before I
get the program crashes with the message "Fatal error: exception
Stack_overflow". At the time of the crash, nearly 2 GB of memory are in use.
(My machine -- AMD64 architecture -- has 8 GB of memory, so insufficient
memory is not the issue.)
Two questions:
1. How can I overcome the Stack_overflow error? (I'm already compiling with
ocamlopt rather than ocamlc, which seems to have increased the stack size
from 500 MB to 2 GB.) I'd like to be able to use the full 8 GB on my
machine.
2. How can I implment a more efficient hash table? My Ocaml program seems to
require 10x more memory than under C++.
My code appears below. Thank you very much.
--John
--------------
exception SplitError
let read_whole_chan chan =
let movieMajor = Hashtbl.create 777777 in
let rec loadLines count =
let line = input_line chan in
let murList = Pcre.split line in
match murList with
| m::u::r::[] ->
let rFloat = float_of_string r in
Hashtbl.add movieMajor m (u, rFloat);
if (count mod 10000) == 0 then Printf.printf "count: %d, m:
%s, u: %s, r: %f \n" count m u rFloat;
loadLines (count + 1)
| _ -> raise SplitError
in
try
loadLines 0
with
End_of_file -> ()
;;
let read_whole_file filename =
let chan = open_in filename in
read_whole_chan chan
;;
let filename = Sys.argv.(1);;
let str = read_whole_file filename;;
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next reply other threads:[~2008-02-19 23:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-19 23:01 John Caml [this message]
2008-02-19 23:34 ` [Caml-list] " Gabriel Kerneis
2008-02-19 23:36 ` Gerd Stolpmann
2008-02-19 23:51 ` Francois Rouaix
2008-02-20 9:37 ` Berke Durak
2008-02-20 9:56 ` Berke Durak
2008-02-20 12:48 ` Richard Jones
2008-02-20 15:54 ` Oliver Bandel
2008-02-21 22:45 ` John Caml
2008-02-22 0:33 ` Richard Jones
2008-02-24 5:39 ` John Caml
2008-02-22 14:19 ` Brian Hurt
[not found] <fa.XXbywsQknpl7bhlesWN8vFLM58c@ifi.uio.no>
[not found] ` <55e81f00-5ef7-4946-9272-05595299e114@41g2000hsc.googlegroups.com>
2008-02-20 5:18 ` John Caml
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