What is the GLops of Mali T628MP6? Can't get 17 flops per pipe using OpenGL.

Hi chrisvarns,

That's really amazing.

According to your explain, to reach the peak throughput, the program should be:

case 1:

1. tmp = vec4(dot(color_out5, color1)); 
2. color_out5 = tmp * color_out5; 
3. color_out1 = tmp + color_out1;

But in common program, it should be:

case 2:

1. tmp = vec4(dot(color_out5, color1)); 
2. color_out5 = tmp * color_out5 + color_out1; 

or !

case 3:

1. tmp = vec4(dot(color_out5, color1)); 
2. color_out5 = tmp * color_out5; 
3. color_out1 = color_out5 + color_out1;

But the throughput of case 2&3 is only half of case 1. So is this the hardware limitation? If I want to achieve high performance, I need to write shaders like case 1?

Hi chrisvarns,

That's really amazing.

According to your explain, to reach the peak throughput, the program should be:

case 1:

1. tmp = vec4(dot(color_out5, color1)); 
2. color_out5 = tmp * color_out5; 
3. color_out1 = tmp + color_out1;

But in common program, it should be:

case 2:

1. tmp = vec4(dot(color_out5, color1)); 
2. color_out5 = tmp * color_out5 + color_out1; 

or !

case 3:

1. tmp = vec4(dot(color_out5, color1)); 
2. color_out5 = tmp * color_out5; 
3. color_out1 = color_out5 + color_out1;

But the throughput of case 2&3 is only half of case 1. So is this the hardware limitation? If I want to achieve high performance, I need to write shaders like case 1?

I can't talk publicly about the hardware internals at this level unfortunately, but suffice to say, the performance of a particular shader is completely dependent on the way that shader is written, and how it maps to/schedules on a particular architecture. It is not expected that all code will execute at the peak theoretical throughput, so you should not worry about achieving this target in practice. Best practice advice for writing shaders for Mali GPUs can be found in the Optimization Guide available at Mali GPU Application Optimization Guide v3.0 « Mali Developer Center, and this is the bulk of the public information on the subject of optimization for Mali GPUs.

Hope this helps,

Chris

Hi chrisvarns,

Thanks for your reply. It's really helpful.

Hi chrisvarns,

I find a strange thing. If I modify your code, change precision from mediump to highp, the cycles is also 6...

precision highp float; 
varying vec4 color5; 
varying vec4 color6; 
varying vec4 color1; 


vec4 color_out5a; 
vec4 color_out1a; 
vec4 tmpa; 
vec4 color_out5b; 
vec4 color_out1b; 
vec4 tmpb; 


void main(void) 
{ 
        color_out5a = color5; 
        color_out1a = color1; 
        color_out5b = color5; 
        color_out1b = color1; 
        tmpa = vec4(dot(color_out5a, color1)); 
        color_out5a = tmpa * color_out5a; 
        color_out1a = tmpa + color_out1a; 
        tmpb = vec4(dot(color_out5b, color1)); 
        color_out5b = tmpb * color_out5b; 
        color_out1b = tmpb + color_out1b; 
        tmpa = vec4(dot(color_out5a, color1)); 
        color_out5a = tmpa * color_out5a; 
        color_out1a = tmpa + color_out1a; 
        tmpb = vec4(dot(color_out5b, color1)); 
        color_out5b = tmpb * color_out5b; 
        color_out1b = tmpb + color_out1b; 
        tmpa = vec4(dot(color_out5a, color1)); 
        color_out5a = tmpa * color_out5a; 
        color_out1a = tmpa + color_out1a; 
        tmpb = vec4(dot(color_out5b, color1)); 
        color_out5b = tmpb * color_out5b; 
        color_out1b = tmpb + color_out1b; 
        tmpa = vec4(dot(color_out5a, color1)); 
        color_out5a = tmpa * color_out5a; 
        color_out1a = tmpa + color_out1a; 
        tmpb = vec4(dot(color_out5b, color1)); 
        color_out5b = tmpb * color_out5b; 
        color_out1b = tmpb + color_out1b; 
        gl_FragColor = color_out1a * color_out5a + color_out1b * color_out5b; 
} 

And when I change the input, the cycles doubles...

precision mediump float; 
varying vec4 color5; 
varying vec4 color6; 
varying vec4 color1; 
varying vec4 color2;
varying vec4 color3;


vec4 color_out5a; 
vec4 color_out1a; 
vec4 tmpa; 
vec4 color_out5b; 
vec4 color_out1b; 
vec4 tmpb; 


void main(void) 
{ 
        color_out5a = color5; 
        color_out1a = color1; 
        color_out5b = color2; 
        color_out1b = color3; 
        tmpa = vec4(dot(color_out5a, color1)); 
        color_out5a = tmpa * color_out5a; 
        color_out1a = tmpa + color_out1a; 
        tmpb = vec4(dot(color_out5b, color1)); 
        color_out5b = tmpb * color_out5b; 
        color_out1b = tmpb + color_out1b; 
        tmpa = vec4(dot(color_out5a, color1)); 
        color_out5a = tmpa * color_out5a; 
        color_out1a = tmpa + color_out1a; 
        tmpb = vec4(dot(color_out5b, color1)); 
        color_out5b = tmpb * color_out5b; 
        color_out1b = tmpb + color_out1b; 
        tmpa = vec4(dot(color_out5a, color1)); 
        color_out5a = tmpa * color_out5a; 
        color_out1a = tmpa + color_out1a; 
        tmpb = vec4(dot(color_out5b, color1)); 
        color_out5b = tmpb * color_out5b; 
        color_out1b = tmpb + color_out1b; 
        tmpa = vec4(dot(color_out5a, color1)); 
        color_out5a = tmpa * color_out5a; 
        color_out1a = tmpa + color_out1a; 
        tmpb = vec4(dot(color_out5b, color1)); 
        color_out5b = tmpb * color_out5b; 
        color_out1b = tmpb + color_out1b; 
        gl_FragColor = color_out1a * color_out5a + color_out1b * color_out5b; 
} 

So I think your code is somehow optimized.

According to peterharris's answer in the thread How many gigaflops GPU MALI T624 MP6 reaches?,

"Most graphics content heavily uses fp16 rather than fp32 - for Mali this means we can get (approximately) double the performance in terms of peak FP16 flops throughput". That means we can get double  peak throughput.

How can we get that throughput?