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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
"Gilles Fedak" <fed### [at] lri fr> wrote in message
news:3AA91F44.CF4CF8F6@lri.fr...
> Tom Melly wrote:
> > What version are you going to run? Also, presumably you won't
> > allow any external files (image maps and hfs, etc.) or i/o
> > access.
> Well, we can support several versions as I understand there are
> currently two main versions of PovRay, PovRay 3.1 and Patched or
> MegaovRay.
At least three versions of MegaPOV.. :-) Things like particle
systems, cloth simulation, procedural texturing, aren't there yet..
> Concerning I/O, actually we work as this: if you want to submit a
> task (of an application in general) you give a file which is the
> stdin file, a zip file which is a compressed directory containing
> all the files requested for the execution of the task, and the
> command line.
The issue here is that Povray in and of itself allows you to
directly open files, execute command, etc..
> The worker (remote PC) unzips the dir, jumps into, execute the
> command line, inject the stdin file. So you see that's it is quite
> simple and ad hoc. Right now we don't support some kind of
> "throttle" mecanism for limiting bandwith, or size of
> the genrated files.
But thats the kicker.. I can then have a script that opens any
file, and can read and write from/to it. I could make a .rhosts
entry.. :-(
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I appreciate your considering POV, but I wouldn't use this. It's way too
dangerous, and would take too much of my resources.
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Gilles Fedak wrote:
>
> For the i/o point of view, we can easly restrict the size of the input
> file to few Ko :)
>
Restricting the size of the input file is not enough, because even a tiny input
file can easily generate a massive scene if it uses iterative elements such as
loops and recursive macros. Disallowing such elements is probably not an option,
because many people rely on them quite heavily.
As far as I can see, running a parse test on the server is the only reliable way
of evaluating a submitted scene. The test sould check that both parse time and
(more importantly IMO) memory usage are within acceptable limits. Of course with
animations, a test parse must be performed for every frame, because different
clock values can execute different branches in the script. All this may or may
not put too much stress on the server...
--
Margus Ramst
Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg
Home page http://www.hot.ee/margusrt
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"Tony[B]" wrote:
>
> I appreciate your considering POV, but I wouldn't use this. It's way too
> dangerous, and would take too much of my resources.
On the point of the ressources, you should keep in mind that the machine
is used only when there are no interactive activity (screensaver) or
when the CPU is idle ( an activity under a low treshold ).
--
Gilles Equipe Architectures Paralleles Tel 33 01-69-15-42-25
FEDAK LRI bat 490 Fax 33 01-69-15-65-86
------ Universite Paris-Sud email: fed### [at] lrifr
XtremWeb F-91405 ORSAY Cedex http://www.lri.fr/~fedak
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> With 480 clients out there on
> the net, I could have my image in a half hour instead of 3 days...
That's the point.
> The world is full of deviants, and it looks like a lot of them
> own computers now.
C'est la vie :)
> Also, denial attacks will be common -- particularly in the case of something
> like POV, it wouldn't take much effort to submit a bunch of files that would
> effectively prevent anybody from ever getting anything else processed. The
> script I mentioned earlier takes about two hours to render as just a 160x100
> thumbnail and lengthy rendering times definitely wasn't my goal...
Yes, an idea was to calculate few pixels, that could serve both as
predicting the rendering time of the scene, and as certificate for
correctness of the computations.
BTW I have one question about the way you distribute the rendering on
your different PCs. How does the distribution handles the various
frequency of the processors. I mean how the load is distributed to the
processors, statically or dynimically ?
--
Gilles Equipe Architectures Paralleles Tel 33 01-69-15-42-25
FEDAK LRI bat 490 Fax 33 01-69-15-65-86
------ Universite Paris-Sud email: fed### [at] lrifr
XtremWeb F-91405 ORSAY Cedex http://www.lri.fr/~fedak
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>
> But thats the kicker.. I can then have a script that opens any
> file, and can read and write from/to it. I could make a .rhosts
> entry.. :-(
I mean that you don't have access to files outside of a temporary
directory.
--
Gilles Equipe Architectures Paralleles Tel 33 01-69-15-42-25
FEDAK LRI bat 490 Fax 33 01-69-15-65-86
------ Universite Paris-Sud email: fed### [at] lrifr
XtremWeb F-91405 ORSAY Cedex http://www.lri.fr/~fedak
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Gilles Fedak wrote:
> Idea is to use the idle time of computers to render scenes provided by
> any one.
> Xtremweb allows the distribution of applications and the computing of
> tasks without to much effort, and there are clients available for Linux
> and Windows.
> Povray is for us a good test case for the platform.
> So what do you think about the usefulness of such a project ?
While I've no doubt about Povray being a good test case for this, the main
problem is about the usefulness of it for end users - a least for those who
create stills. Scenes that render slowly (let's say below 10 pps - roughly
an overnight render at 800*600) and that could benefit from it are often
(but not always) ones that also use large amounts of memory and disc space,
which would make their distribution uneasy. While there's usually no formal
relationship between render speed and memory/storage space requirements,
there's a practical one which is the price to pay for scene complexity :
several reflective/refractive objects in a scene involving high-quality
radiosity will make the scene crawl and the memory use rise.
Typically, people who have to meet deadlines for certain raytracing
competitions would be in cases like this ;-)
G.
--
**********************
http://www.oyonale.com
**********************
Graphic experiments
Pov-ray gallery
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"Gilles Fedak" <fed### [at] lrifr> wrote in message
news:3AAA1D58.311A36C5@lri.fr...
> > With 480 clients out there on
> > the net, I could have my image in a half hour instead of 3 days...
> That's the point.
I didn't gather from your original explanation that you intended to break up
the render, it sounded more like you were talking about farming out
animation frame rendering. But if we agree, hey, great!
> Yes, an idea was to calculate few pixels, that could serve both as
> predicting the rendering time of the scene, and as certificate for
> correctness of the computations.
I see two problems with that plan as a test of fitness. First, if they can
figure out where you do the test renders, they can *easily* make that area
render quickly -- maybe even if you use multiple areas (for example, by
carefully placing bounding boxes). The second problem is the converse -- I
think it would be easy to make the small-area test-render take a very, very
long time. For example, layers of transparency, lots of lights, fog, high
max trace level, etc. Then I slam a few of those into your server and the
test-renders shut it down.
And trust me, I hate being the devil's advocate on this. I would love to
have distributed rendering...
> BTW I have one question about the way you distribute the rendering on
> your different PCs. How does the distribution handles the various
> frequency of the processors. I mean how the load is distributed to the
> processors, statically or dynimically ?
My distribution method is a little something I call "doing it by hand". :)
There isn't anything automated about how I do it now (unfortunately), other
than copying files around on the network and using remote control software
to kick off rendering on the other machines. I am toying with a couple ideas
but I haven't actually written any code yet.
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On 2001-03-10 03:06, Margus Ramst <mar### [at] peakeduee> wrote:
>Gilles Fedak wrote:
>>
>> For the i/o point of view, we can easly restrict the size of the input
>> file to few Ko :)
>>
>
>Restricting the size of the input file is not enough, because even
>a tiny input file can easily generate a massive scene if it uses
>iterative elements such as loops and recursive macros. Disallowing such
>elements is probably not an option, because many people rely on them
>quite heavily.
You would have to put restrictions on the process. Most Unixes offer
quite a few "resource limits" which you can set. For distributed povray
the most important are IMHO:
RLIMIT_CPU
(limits the total CPU usage for one job)
RLIMIT_DATA, RLIMIT_STACK, RLIMIT_CORE
(limits the memory usage of a single process not all unixes have all
of these)
RLIMIT_NPROC
(limits the number of processes per user)
RLIMIT_NOFILE
(limits the number of open files per process)
Together with quotas, a chrooted environment and a positive nice factor,
the povray process(es) would be restricted from disturbing their host
computer.
What is sorely missing in standard Unix is a way to restrict network
connections: There are some approaches to that problem, but nothing
wide-spread yet (I'm guessing that a capability-based system will win
out, though). As long as a locally installed version of povray is run,
this isn't a problem, though, since povray doesn't talk across the net.
>As far as I can see, running a parse test on the server is the only
>reliable way of evaluating a submitted scene. The test sould check that
>both parse time and (more importantly IMO) memory usage are within
>acceptable limits. Of course with animations, a test parse must be
>performed for every frame, because different clock values can execute
>different branches in the script.
You can leave this to the slave servers: They can check whether there is
some output produces within a given time. If there isn't, they'll kill
the process and report failure.
hp
--
_ | Peter J. Holzer | All Linux applications run on Solaris,
|_|_) | Sysadmin WSR | which is our implementation of Linux.
| | | hjp### [at] wsracat |
__/ | http://www.hjp.at/ | -- Scott McNealy, Dec. 2000
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On 2001-03-09 15:41, Gilles Fedak <fed### [at] lrifr> wrote:
>We plan to release a "peer to peer" Povray using the Xtremweb
>(http://xtremweb.net) global computing Platform.
I have downloaded the program, but I couldn't find much information on
how it works, and - most importantly - no source code on the site.
I don't like to run servers on my machines unless I have a clear idea of
what they do - of course some are just too large to audit completely
even if the source code is available, but the small size of the .jar and
.so make this entirely feasible.
hp
--
_ | Peter J. Holzer | All Linux applications run on Solaris,
|_|_) | Sysadmin WSR | which is our implementation of Linux.
| | | hjp### [at] wsracat |
__/ | http://www.hjp.at/ | -- Scott McNealy, Dec. 2000
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