MNIST test fails to run on Radeon 8750M

[battlesnake]

Radeon 8750M on HP Probook 470 G1

clinfo:

Number of platforms                               1
  Platform Name                                   Clover
  Platform Vendor                                 Mesa
  Platform Version                                OpenCL 1.1 MESA 11.0.4
  Platform Profile                                FULL_PROFILE
  Platform Extensions                             cl_khr_icd
  Platform Extensions function suffix             MESA

  Platform Name                                   Clover
Number of devices                                 1
  Device Name                                     AMD OLAND (DRM 2.42.0, LLVM 3.7.0)
  Device Vendor                                   AMD
  Device Vendor ID                                0x1002
  Device Version                                  OpenCL 1.1 MESA 11.0.4
  Driver Version                                  11.0.4
  Device OpenCL C Version                         OpenCL C 1.1 
  Device Type                                     GPU
  Device Profile                                  FULL_PROFILE

Error:

initializing clblas
cl/activate.cl build log: 
input.cl:28:23: warning: implicit declaration of function 'tanh' is invalid in C99
input.cl:11:42: note: expanded from macro 'ACTIVATION_FUNCTION'
unsupported call to function tanh in activate

[battlesnake]

I'm guessing that my OpenCL compiler/hardware doesn't support tanh

[hughperkins]

Yes.... that's two of you now... but looking at http://www.notebookcheck.net/AMD-Radeon-HD-8750M.87147.0.html seems this card supports OpenCL 1.2?

[hughperkins]

(Had a browse through the AMD drivers download, and came up with http://support.amd.com/en-us/download/desktop?os=Linux+x86_64 , but it didnt say what version of OpenCL these support... might be worth a shot though?)

(Edit: ah, per http://wiki.cchtml.com/index.php/Hardware , seems like maybe this driver doesnt support HD8750M? Kind of hard to tell...)

[hughperkins]

(Note that I'm pretty sure opencl 1.1 itself solidly supports tanh: https://www.khronos.org/registry/cl/sdk/1.1/docs/man/xhtml/tan.html )

[battlesnake]

I'm running the open-source driver, which could be why it is at v1.1

[hughperkins]

Ok. Maybe you can add in tanh :-) I think you can construct it as ( e^x - c^(-x) ) / ( e^x + e^(-x) ). Or... you could hack the DeepCL code to use this. In cl/activate.cl, simply replace tanh(output) with this expression.

[battlesnake]

I know :) I'm just curious as to why the OpenCL compiler can't already do that - maybe I should submit a bug report for mesa

[hughperkins]

Well... I guess you could modify their code. But... I'm curious how this could be running on your GPU. It seems like Clover is compiling the opencl itself, and I doubt it's compiling into AMD ISA? (ie http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2013/07/AMD_GCN3_Instruction_Set_Architecture.pdf and so on ). So, seems like it might be running in software, on your CPU?

[battlesnake]

Could be, although I'd be amazed if my Haswell + Intel's drivers couldn't handle tanh!

[hughperkins]

So, what I think is, Clover runs your OpenCL code, just like a script, like running something in Python and so on. I'm fairly sure that no OpenCL code is actually sent to your CPU, to run as Intel OpenCL.

OpenCL => Clover OpenCL Scripting engine => executes as normal x86 program, inside Clover

(Edit: I should have just used hte 'Edit' button really :-P Not sure why I didnt.... )

(Edit2: but I'm not really sure what Clover is doing. Scripting would sound too slow. But compiling to x86 on the fly would sound strange too. But compiling to AMD ISA seems unlikely. Soo... ????)

[battlesnake]

You're right, Clover runs on CPU. Given this, I'm amazed that it doesn't support tanh...

[hughperkins]

:-)

[hughperkins]

Hi. Apparently I'm wrong. Clover does run on GPU :-) See Element-Research/rnn#41