News AMD shows off DX12-related rendering advances that make game engines more efficient and less dependent on the CPU

[Admin]

AMD has unveiled expanded Work Graph functionality by adding draw calls and mesh nodes. This lets the GPU control draw calls and mesh shaders independently from the CPU.

AMD shows off DX12-related rendering advances that make game engines more efficient and less dependent on the CPU : Read more

 

[Metal Messiah.]

AMD showed off benchmark numbers of Work Graphs with mesh shaders running on an RX 7900 XTX, revealing a 64% performance improvement compared to normal Work Graphs without mesh shaders applied.

demo shows a 64% improvement​

Oh no, that's not correct. You got it wrong.

In fact the traditional "ExecuteIndirect" method took 64% longer to render a frame compared to Work Graphs, so in other words, the new method is only 39% faster.

So it's not a 64% performance improvement , rather a mere 39%. ExecuteIndirect was 64% slower.

Another point to be noted in this early demo is that AMD also showcased how the API-level feature "Multi-draw indirect", was prevented from being "underutilized" via work graphs.

 

[digitalgriffin]

Oh no, that's not correct. You got it wrong.

In fact the traditional "ExecuteIndirect" method took 64% longer to render a frame compared to Work Graphs, so in other words, the new method is only 39% faster.

So it's not a 64% performance improvement , rather a mere 39%. ExecuteIndirect was 64% slower.

Another point to be noted in this early demo is that AMD also showcased how the API-level feature "Multi-draw indirect", was prevented from being "underutilized" via work graphs.

Math checks out

1/1.64 - 1 = .39 or 39% But that is significant. So original speed CPU * .6907 = new draw time GPU.
new draw time (GPU) * 1.64 = old draw time (CPU)

Interesting claim. But as it is now, draw engines don't take advantage of all the CPU threads as is. If you have 24 threads, you can have 24 draw calls being processed. But that just doesn't happen today. And part of this is because draw calls are what's known as composited. IE: Draw Right Arm. Draw Left Arm, Draw Body. Draw Arm, Draw weapson, Draw Clothes =>Assemble Draw entire character. This is what a draw tree looks like. Thus the last step is dependant upon the first 6, creating a delay. It takes a very talented developer good with threads to be able to keep the stack of all available threads full.

Now admittingly the GPU schedular can dispatch many more draw calls at once. Basically you are moving the CPU drivers to the GPU and executing there. But until the calling threads are properly written, it's much adu about nothing.

 

[Metal Messiah.]

Also, it seems too early to say how Work Graphs API will translate to gaming performance improvements. The other issue is that it'll be up to game developers to implement the API, which will likely take time.

Let's not forget that MS launched DX12 Mesh Shaders a few years ago. And right now there is only ONE game that takes advantage of them, i.e "Alan Wake 2".

The game could be played on non-supported hardware/GPU though, but the performance was god-awful, 'cause the vertex shader pipeline, i.e. the traditional fallback geometry pipeline was busted. BTW, there's no point in adding a Mesh shader pipeline to an old game though, as they're not performance limited by the vertex processing stage.

Also, the developers would need to create a whole set of polygon-rich models and worlds, and then ensure there's a large enough user base of hardware out there, to justify the time spent on going down the mesh shader route.

Most games don't use huge amounts of triangles to create the world. And it's not surprising to know that Developers kept this aspect quite light, instead using vast numbers of compute and pixel shaders to make everything look good, at least for the most part.

So yeah, even though 'Work Graphs' sounds cool, it's not sure many developers will use it. Unless, of course, the next PlayStation and Xbox consoles support it.


EDIT:

Thanks for the input, digitalgriffin ! Just saw your comment while posting this.

 

[thisisaname]

Also, it seems too early to say how Work Graphs API will translate to gaming performance improvements. The other issue is that it'll be up to game developers to implement the API, which will likely take time.

Let's not forget that MS launched DX12 Mesh Shaders a few years ago. And right now there is only ONE game that takes advantage of them, i.e "Alan Wake 2".

The game could be played on non-supported hardware/GPU though, but the performance was god-awful, 'cause the vertex shader pipeline, i.e. the traditional fallback geometry pipeline was busted. BTW, there's no point in adding a Mesh shader pipeline to an old game though, as they're not performance limited by the vertex processing stage.

Also, the developers would need to create a whole set of polygon-rich models and worlds, and then ensure there's a large enough user base of hardware out there, to justify the time spent on going down the mesh shader route.

Most games don't use huge amounts of triangles to create the world. And it's not surprising to know that Developers kept this aspect quite light, instead using vast numbers of compute and pixel shaders to make everything look good, at least for the most part.

So yeah, even though 'Work Graphs' sounds cool, it's not sure many developers will use it. Unless, of course, the next PlayStation and Xbox consoles support it.


EDIT:

Thanks for the input, digitalgriffin ! Just saw your comment while posting this.

Just what I was thinking, it sounds great but they have to get programmers to use it.

 

[Alvar "Miles" Udell]

Would have been far better had it released with DX12 in 2015 when CPUs were comparatively weak. Something tells me with a "modern" CPU (say Zen 3 or Intel equivalent or newer) the performance gain will be smaller, if even statistically significant, especially on AMD's unified design vs nVidia's dedicated design.

 

[gruffi]

Oh no, that's not correct. You got it wrong.

In fact the traditional "ExecuteIndirect" method took 64% longer to render a frame compared to Work Graphs, so in other words, the new method is only 39% faster.

So it's not a 64% performance improvement , rather a mere 39%. ExecuteIndirect was 64% slower.

Another point to be noted in this early demo is that AMD also showcased how the API-level feature "Multi-draw indirect", was prevented from being "underutilized" via work graphs.

That's wrong. It's indeed a 64% performance improvement. It's actually simple math. I don't know why this is so hard for people to understand. If lower means better, usually having times, then just use the reciprocal of the values.

In the same time ExecuteIndirect can finish only ~60.98% of the task (100%/1.64). Now normalize that to 100%, 100%*100%/60.98% = 164%. So, Work graphs shows a 64% performance improvement compared to ExecuteIndirect.

 

[ien2222]

That's wrong. It's indeed a 64% performance improvement. It's actually simple math. I don't know why this is so hard for people to understand. If lower means better, usually having times, then just use the reciprocal of the values.

In the same time ExecuteIndirect can finish only ~60.98% of the task (100%/1.64). Now normalize that to 100%, 100%*100%/60.98% = 164%. So, Work graphs shows a 64% performance improvement compared to ExecuteIndirect.

Actually no.

And it's easy math to check with using the equation of: Original - (original x improvement %) which will give you the value of the better performance. So, if we use 64% we'd have 1.64 - (1.64 x 64%) = .59, which is incorrect. Using 39% we have 1.64 - (1.64 x 39%) = 1, which is correct

A simpler way of showing that 64% is wrong is that we're working in a scale of 0-100%, 0% improvement gives you the same value as the original, 100% improvement means the value is 0. Given that 64% > 50% and a 50% improvement should give us half the original; 1.64/2 = .82 meaning 64% should be even less than that which is incorrect as we know the correct value is 1.

 

[TechyIT223]

It would be better if the devs show some actual game demo footage of this new tech.

Wanna see how much this makes any difference in real world gameplay😉

 

[gruffi]

Actually no.

And it's easy math to check with using the equation of: Original - (original x improvement %) which will give you the value of the better performance. So, if we use 64% we'd have 1.64 - (1.64 x 64%) = .59, which is incorrect. Using 39% we have 1.64 - (1.64 x 39%) = 1, which is correct

A simpler way of showing that 64% is wrong is that we're working in a scale of 0-100%, 0% improvement gives you the same value as the original, 100% improvement means the value is 0. Given that 64% > 50% and a 50% improvement should give us half the original; 1.64/2 = .82 meaning 64% should be even less than that which is incorrect as we know the correct value is 1.

Actually yes. It's 64% more performance, not 39%. Your formula is wrong. Generally calculating the improvement, it should be "improved - (original x improvement%) = 1" or "improved = 1 + (original x improvement%)". Subtracting "original x improvement%" from the original makes absolutely no sense.

100% improvement also doesn't mean the value is 0. In this case 100% improvement would mean that the original value would have halved. If the value was 0, or at least close to 0, then the improvement would need to be infinite.

But I already showed the correct calculation before. Your calculations are nonsense. But it shows what I said before. A lot of people don't understand this math.

 

[ien2222]

Actually yes. It's 64% more performance, not 39%. Your formula is wrong. Generally calculating the improvement, it should be "improved - (original x improvement%) = 1" or "improved = 1 + (original x improvement%)". Subtracting "original x improvement%" from the original makes absolutely no sense.

100% improvement also doesn't mean the value is 0. In this case 100% improvement would mean that the original value would have halved. If the value was 0, or at least close to 0, then the improvement would need to be infinite.

But I already showed the correct calculation before. Your calculations are nonsense. But it shows what I said before. A lot of people don't understand this math.

*sigh*

I went to college for Mathematics and Computer Science, heck, nearly ended up with minors in physics, chemistry, music, and economics, and stuff like this is what I've done for work among other things.

This is my wheelhouse.

We aren't strictly talking about how much better one algorithm is vs the other in the absolute sense where we can have an algorithm that's 10000000000000000000000000000000% faster than the other, we're talking about the improvement in results. In this context what I said is correct, along with Metal and Griffin.

Edit: The problem is most everyone is only used to some value increasing as performance goes up i.e. using A gives us 100 units and going with B gives also 164 units. In this case it's a 64% increase with B. Easy enough, to figure out as it's (improvement - original)/original x 100%.

However, when increased performance results in decreased units, you calculate it differently. Generally the limit to which it can be reduced to is 0 or some positive number and this equation for that is: performance increase% = (original - improvement)/original x 100%. From this equation is what I derived the equation in my first post:

(O - i)/O *100% = PI%
(O-i)/O= (PI%/100%)
O-i = (O*(PI%/100%)
-i = (O*(PI%/100%) - O
i = O - (O*(PI%/100%)

improved value = original value - (original value * performance improvement%)

 

[Dodecahedron]

That's wrong. It's indeed a 64% performance improvement. It's actually simple math. I don't know why this is so hard for people to understand. If lower means better, usually having times, then just use the reciprocal of the values.

In the same time ExecuteIndirect can finish only ~60.98% of the task (100%/1.64). Now normalize that to 100%, 100%*100%/60.98% = 164%. So, Work graphs shows a 64% performance improvement compared to ExecuteIndirect.

You are right. It is common to define performance as "amount of work" / time (e.g. here, slide 7), W/t. When two methods (m1 and m2) perform the same task in times t1 and t2, relative performance of m1 w.r.t. m2 is m1/m2 = (W/t1) / (W/t2) = t2/t1. So, you can just divide the larger time by the smaller one to get the relative performance of the faster method. This formula is also given, e.g., here (slide 4).

It is of course possible to define performance in some other way. However, it is important to have a consistent definition and then adapt any formulas to match the definition. Then, the meaning of "A is x % faster than B" does not depend on whether a test program reports a running time or the number of tasks completed in a given time.

 

[annymmo]

Work Graphs are turning out to be a fantastic feature.
With such a big impact they're worthy of a new major DirectX version.

The transition to Work Graphs needs to be done for everything: the rasterizer, Pixel Shaders, Ray Tracing, Path Tracing, etc.

Maybe the combination of Work Graphs and Mesh Shaders into Mesh Nodes is unlocking some kind of the whole being more than the sum of it's parts type of synergy. Does Mesh Nodes being described as Amplification Shaders on steroids mean Mesh Nodes will replace Amplification Shaders?

The benchmark results being described as super early numbers is super interesting.
Does this mean performance improvements will be much, much enormously bigger once the software and hardware are mature/ not (super) early anymore?

"'Mesh nodes' really close the loop in terms of providing an end-to-end replacement for Execute Indirect and moving the GPU programming model forward,"

Will Work Graphs (and combining with previous improvements such as Mesh Shaders) finally complete the elimination of all sub-optimal cpu-gpu communication (and other bottlenecks) without further improvements possible?

 

[bit_user]

It is common to define performance as "amount of work" / time

Looking at it this way, you'd have to agree that the baseline method is 61.0% as fast as the improved method, since we're told it takes 1.64 times as long to do the same work. If it takes me 1.64 times as long to swim the same distance as you, I'm swimming 61% as fast. Let's say it takes me 1.64 hours to swim a mile and you can swim 1 mile in an hour. So, I'm swimming at 0.61 miles per hour. How can you say anything other than that I'm moving 61% as fast?

However, where things get interesting is when you predict the impact on frame rates each method could have. To keep things simple, let's say the frame rendering time for the baseline method is 1.64 milliseconds, while the rendering time for the improved method is a clean 1 millisecond. That yields frame rates of 610 fps and 1000 fps, respectively. Now, how much of an improvement is 1000 fps over 610 fps? 64%!

So, my take is that neither way of looking at it is exactly wrong. But, if we're talking about how much improvement in frame rates the technique could yield, it'd indeed be a 64% improvement!

I think it's often interesting when we hit upon a question of "which perspective is more useful?" - they tend to invite a step back so one can view the problem in context.