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Re: [Manta] Image degrades as more processors get involved!


Chronological Thread 
  • From: "Christian Odom" <cnsodom@gmail.com>
  • To: "Solomon Boulos" <boulos@cs.utah.edu>
  • Cc: "Dirk Reiners" <dirk@infiscape.com>, manta@sci.utah.edu
  • Subject: Re: [Manta] Image degrades as more processors get involved!
  • Date: Wed, 5 Sep 2007 21:09:08 -0400
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On 9/5/07, Solomon Boulos <boulos@cs.utah.edu> wrote:
Hi Dirk and Christian,

The change camera stuff looks good.  As you mentioned (Dirk), using
Manta's transaction interface does correctly handle the thread-safety
for the Camera (the transactions are only called after rendering has
completed for that frame).

Try running Manta with SSE disabled on your amd64 box by turning SSE
off in the cmake settings (I believe you did this for the ia64 run as
well).

Do I need to remove the flags:   -msse -msse2 -msse3 as well?
I'll post a new pic of the results.  There still seems to be some noise, but it has moved.

Does the same problem occur for bin/manta with your camera? 

That is the last picture I posted.  So yes the problem is there. Im not sure if the noise on the sphere and in the bottom of the left frame is the same type of noise.
It doesnt move like when I use multiple processors.  If I just run bin/manta with the default camera everything looks fine.

 Your
scene setup seems slightly different (is it just a hard coded color
change in StandAlone/manta.cc or is it something more?) so I'd like
to rule that out as a possible problem.

I swapped the y and z axis in the scene setup.  I didnt move the lights so I imagine that is why the color is off.
I repeated all runs with the default scene in its true form and the noise still exist. 

Material* plane_matl = new Phong(new CheckerTexture<Color>(Color(RGBColor(.6,.6,.6)),

Color(RGBColor(0,0,0)),

Vector(1,0,0),

Vector(0,0,1)),

new Constant<Color>(Color(RGBColor(.6,.6,.6))),

32,

new CheckerTexture<ColorComponent>

((ColorComponent)0.2,

(ColorComponent)0.5,

Vector(1,0,0),

Vector(0,0,1)));

Group* world = new Group();

Primitive* floor = new Parallelogram(plane_matl, Vector(-20,0,-20),

Vector(40,0,0), Vector(0,0,40));

// Setup world-space texture coordinates for the checkerboard floor

UniformMapper* uniformmap = new UniformMapper();

floor->setTexCoordMapper(uniformmap);

world->add(floor);

world->add(new Sphere(red, Vector(0,1.2,0), 1.0));
//END CODE SEGMENT


I wouldnt think this matters, but I wanted to let you guys know just in case.
To get manta to compile on the ia64 machine we had to comment out line 90 of CPUTime.cc

CPUTime::SysClock CPUTime::currentTicks()
{
if (!initialized) initialize();

unsigned int a, d;
//not working on ia64 gcc 4.1.2 asm volatile("rdtsc" : "=a" (a), "=d" (d));
return static_cast<unsigned long long>(a) |
(static_cast<unsigned long long>(d) << 32);
}



 

Solomon

On Sep 5, 2007, at 4:15 PM, Christian Odom wrote:

>
>
> On 9/5/07, Dirk Reiners <dirk@infiscape.com> wrote:
>         Hi Christian,
>
> Christian Odom wrote:
> >
> >
> > On 9/5/07, *Solomon Boulos* <boulos@cs.utah.edu
> > <mailto: boulos@cs.utah.edu>> wrote:
> >
> >     Do you run into the problem with -np 1? Also, would it be
> possible
> >     to get the full copy of your camera implementation instead of
> just
> >     makeRays (which looks okay to me).
> >
> >
> > I am having to forward the X session over the net so it is really
> slow,
> > but from what I can tell the image looks fine with -np 1.
> >
> > I have attached the current MatrixCamera class. I really need to go
> > through and clean it up. Please excuse the mess.
>
> Could you also post the piece of the NetworkUI that sets up the
> Camera?
> I'm a little worried that there might be something in there that's not
> threadsafe. We have worked under the assumption that Manta takes
> care of
> thread-safety for the Camera, but I'm not totally sure.
>
> Certainly.
>
> I have also included a picture of the output when manta is running
> on my laptop with only one processor.  Its an amd64.  There seems
> to be a little noise in the image.  A little on the sphere and a
> little on the bottom left of the plane.  When there are multiple
> processors the "noise" moves around the image.  This is not the
> case with only one processor.
>
>         Dirk
>
>
>
> --
> Christian Odom
> Graduate Student
> Center for Advanced Computer Studies
> http://www.cacs.louisiana.edu
> Louisiana Immersive Technologies Enterprise
> http://www.lite3d.com
> <NetworkUI.cc>
> <NetworkUI.h>
> <Screenshot.png>




--
Christian Odom
Graduate Student
Center for Advanced Computer Studies
http://www.cacs.louisiana.edu
Louisiana Immersive Technologies Enterprise
http://www.lite3d.com

Attachment: WithoutSSE.png
Description: PNG image


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