NetNews Usenet Archive 1992 #30/NN_1992_30.iso/spool/comp/os/os2/programm/7031

Internet Message Format | 1992-12-15 | 1.7 KB

Path: sparky!uunet!munnari.oz.au!goanna!steveh
From: [e-mail] (Steven Hayes)
Newsgroups: comp.os.os2.programmer
Subject: malloc()ing huge (> 3 megabyte) data structures
Message-ID: <[e-mail]>
Date: 15 Dec 92 13:55:52 GMT
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 29

Hi people,

I'm working on some neural net software using ICC under OS/2 2.0. I need
to be able to allocate HUGE arrays, around the 3 megabyte mark, and I'm
using an 8 megabyte machine. Thank god for virtual memory ;-)

Ok, so I malloc() the array(s), and everything _appears_ to be fine. I check
that malloc returns non-NULL values, etc, and it _seems_ that everything is
fine. Unfortunately, I'm getting floating point underflow errors when I
start performing operations on the arrays. The underflow errors don't seem
to occur in the same place (IPMD tells me this). I don't understand why this
is happening. Are there bugs in the VM management?

The reason why I think there are some virtual memory and/or compiler bugs
is that my code works _beautifully_ for smallish neural networks (< 2500
nodes and 10000 weights, in NN speak). But start asking the _same_ binary
code to build and train bigger networks results in underflow.

I'm using malloc() instead of DosAllocMem() to retain UNIX portability. I'll
try running the code on a UNIX workstation tomorrow and we'll see what
happens.

If you have any experiences with allocating large chunks of memory please
mail me or follow-up. I'd be most interested to hear from you.

Steve
--
   Steven Hayes                                    |  [e-mail]
   Royal Melbourne Institute of Technology (RMIT)  |  [phone]