GL_MAX_PROGRAM_EXEC_INSTRUCTIONS_NV limitation "per pixel" or "per frame" ?

[Skybuck Flying]

Hello,

I have a little question about GL_MAX_PROGRAM_EXEC_INSTRUCTIONS_NV.

On my NVIDIA GTX 7900 it returns: 4530371

Does this mean each fragment can execute 4.5 million instructions before
being terminated ?

Or does this mean all fragments together can execute at most 4.5 millions
instructions before being terminated ?

So is this limitation "per pixel" or "per frame" ???

Bye,
Skybuck.

[Skybuck Flying]

Hmm to answer my own question... I guess it's per pixel...

Since a frame can be 1920x1200 pixels... which would be: 2304000

So if it were 4.5 million in total.. then that would only be roughly 2
instructions per pixel which would be pretty crappy ;)

So I think it's 4.5 million per pixel ! ;)

Bye,
Skybuck.

[Chris Forone]

from:
http://oss.sgi.com/projects/ogl-sample/registry/NV/fragment_program2.txt

"maximum program execution INSTRUCTION COUNT"

so your shader program can hold up to 4.5M instructions. IMHO it has
nothing to do with the count of pixels except that they have all to go
thru the shader.

greets, chris

[Wolfgang Draxinger]

Skybuck Flying wrote:

> Hello,
>
> I have a little question about GL_MAX_PROGRAM_EXEC_INSTRUCTIONS_NV.
>
> On my NVIDIA GTX 7900 it returns: 4530371
>
> Does this mean each fragment can execute 4.5 million instructions before
> being terminated?

I think the terminology "instruction count" is quite clear: It limits the
length of your program. From your point of view the GPU is a massive
parallel processor, that executes the same program on a very large data
file (the textures and the framebuffer).

> So is this limitation "per pixel" or "per frame" ???

Think about the following: Early generations of shader capable GPUs had an
instruction limit of ~200. I think this should make the answer obvious.

Wolfgang
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OpenGL tip #42:
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