dar1243

How reliable are ShaderAnalyzer timings ?

Discussion created by dar1243 on Jul 16, 2009
Latest reply on Jul 24, 2009 by dar1243

Quick question:

How reliable are ShaderAnalyzer timings ?

I have identical shader in GLSL and HSLS and i'v done performance analysis on it, here are results:

 

radeon 4870 HD

DX9 -> 3.50 cycles  |  4.57 pixels/cycle  | 68 ALU
DX10-> 3.60 cycles  |  4.44 pixels/cycle  | 79 ALU
GLSL-> 4.00 cycles  |  4.00 pixels/cycle  | 82 ALU

radeon 4670 HD

DX9 -> 4.37 cycles  |  1.83 pixels/cycle  | 68 ALU
DX10-> 4.62 cycles  |  1.73 pixels/cycle  | 81 ALU
GLSL-> 4.59 cycles  |  1.74 pixels/cycle  | 82 ALU

 

Seems that DX9 is fastest, then DX10 and at the end GLSL on that same shader (? it is possible at all - the shader will run much slower on GLSL in real life situation ?)

Shader uses 5 texfetches and some alu calculations, input is 5 UV coords (float2), output is single float4, no branches, no integer (or integer like) operations, only mul/add/sqrt/pow/saturate/clamp used,

so why the analysis so differs between apis ?

(for dx9/10 optimalization is level3 - for glsl - no such a choice)

PS. On nvidia tools for shader analysys GLSL/DX9/DX10 performance is almost equal (the glsl is slightly better than DX9/DX10 profiles).

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