Help with CUDA nvcc error in Mandelbulb example Mathematica 11.0 NVIDIA GTX 1070 on Ubuntu

Question

I am exploring the Nvidia GTX 1070 with Mathematica, I tried this example from the Help guide and it fails with a nvcc complier error. A little google research seems to indicate that I need the nvcc complier included with the CUDA Toolkit v8 Release Candidate. The nvcc that Mathematica is executing seems to be embeded somewhere with Mathematica files. I see the CCompilers[] function has abilities to change executable and options, but not sure if this is right path just to see a demo. Any help on best way to proceed would be great, thx!

Generate a Mandelbulb Set with CUDA Functionality example/GenerateAMandelbulbSetWithCUDAFunctionality

mandelbulb = 
 CUDAFunctionLoad[{srcf}, 
  "MandelbulbGPU", {{"Float", _, "Output"}, {"Float", _, 
    "Input"}, {"Integer32", _, "Input"}, "Integer32", "Float", 
   "Float"}, {16}, "UnmangleCode" -> False, 
  "ShellOutputFunction" -> Print]

nvcc fatal: Value 'sm_61' is not defined for option 'gpu-architecture'

Ubunutu 16.04, GeForce GTX 1070 NVIDIA driver 367.44, Mathematica 11.0

I have not installed the CUDA Toolkit, either version 7.5 or 8.0 RC, so I am guessing the nvcc complier is installed by Mathematics software download, which occured for me when I requested the CUDAInformation[] function.

{1 -> {"Name" -> "GeForce GTX 1070", "Clock Rate" -> 1683000, 
   "Compute Capabilities" -> 6.1, "GPU Overlap" -> 1, 
   "Maximum Block Dimensions" -> {1024, 1024, 64}, 
   "Maximum Grid Dimensions" -> {2147483647, 65535, 65535}, 
   "Maximum Threads Per Block" -> 1024, 
   "Maximum Shared Memory Per Block" -> 49152, 
   "Total Constant Memory" -> 65536, "Warp Size" -> 32, 
   "Maximum Pitch" -> 2147483647, 
   "Maximum Registers Per Block" -> 65536, "Texture Alignment" -> 512,
    "Multiprocessor Count" -> 15, "Core Count" -> 480, 
   "Execution Timeout" -> 1, "Integrated" -> False, 
   "Can Map Host Memory" -> True, "Compute Mode" -> "Default", 
   "Texture1D Width" -> 131072, "Texture2D Width" -> 131072, 
   "Texture2D Height" -> 65536, "Texture3D Width" -> 16384, 
   "Texture3D Height" -> 16384, "Texture3D Depth" -> 16384, 
   "Texture2D Array Width" -> 32768, 
   "Texture2D Array Height" -> 32768, 
   "Texture2D Array Slices" -> 2048, "Surface Alignment" -> 512, 
   "Concurrent Kernels" -> True, "ECC Enabled" -> False, 
   "TCC Enabled" -> False, "Total Memory" -> 8505589760}}

Answer 1

Yes, the nvcc compiler is installed with Mathematica, but you can specify the use of another one.

For you the problem seems to be that the architecture sm_61 (this refers to "Compute Capabilities" -> 6.1) is not supported by CUDA 7.5, which is the versions installed with Mathematica 11.0.0. To use sm_61 you have to install CUDA 8 and specify it via "CompilerInstallation" as an option to CUDAFunctionLoad. This is if you really want to use the most recent CUDA features added to CUDA 8 and only available in the NVIDIA Pascal series GPUs. (Note: I do not know if this really works as I have not tested Mathematica 11 with CUDA 8, there might be some other incompatibility).

Unless you are using advanced features of the architecture, which you are not with the mandelbulb example, you should just manually specify a different architecture by using the "CUDAArchitecture" Option of CUDAFunctionLoad. In most cases compute capability 3.5 should be sufficient, which corresponds to setting "CUDAArchitecture"->"sm_35". Most graphics cards support at least "sm_30", so I would choose this if your kernel does not use any advanced features for downwards compatibility reasons.