Fill() regression in 0.3.9

[slayoo]

The following used to work up until 0.3.8 but fails with newer versions without any clear error message:

import ThrustRTC as T
v = T.device_vector("float", 10)
T.Fill(v, T.DVFloat(0.))

Here's a example on fresh Google Colab GPU runtime:

OK on 0.3.8:

[fynv]

I have an impression that 0.3.9 was a broken build which I uploaded to Pypi by accident. And Pypi doesn't allow me to overwrite such packages.

[slayoo]

This problem happens in all versions starting with 0.3.9, 0.3.13 included:

[fynv]

Can't reproduce so far..

[fynv]

Try deleting the file "__ptxcache_\.db". Chance is that there's some broken ptx code.

[slayoo]

Thanks, found the file here on Colab: /content/__ptx_cache__.db but removing it does not change the behavior

[fynv]

There should be some detailed failure message printed through stdout from C code. But using Colab, you can't see it. We shall take a look if it is also reproduced in an enviroment where stdout is visible.

[slayoo]

got it by executing python through shell:

!python -c "import ThrustRTC as T; v = T.device_vector('float', 10); T.Fill(v, T.DVFloat(0.))"

full output:

header_of_structs.h:
1   

saxpy.cu:
1   #define DEVICE_ONLY
2   #include "cstdint"
3   #include "cfloat"
4   #include "cuComplex.h"
5   #include "built_in.h"
6   #include "header_of_structs.h"
7   __device__ float _test;
8   

Errors:
nvrtc: error: invalid value for --gpu-architecture (-arch)

cuMemAlloc() failed with Error code: 2
Error Name: CUDA_ERROR_OUT_OF_MEMORY
Error Description: out of memory
header_of_structs.h:
1   struct _S_1bdca0bfccd39798
2   {
3       typedef _S_1bdca0bfccd39798 CurType;
4        view_vec;
5       float value;
6       template<class _T0>
7       __device__ inline auto operator()(const _T0& idx)
8       {
9       view_vec[idx]=(decltype(view_vec)::value_t)value;    }
10  };
11  

saxpy.cu:
1   #define DEVICE_ONLY
2   #include "cstdint"
3   #include "cfloat"
4   #include "cuComplex.h"
5   #include "built_in.h"
6   #include "header_of_structs.h"
7   __device__ _S_1bdca0bfccd39798 _test;
8   __device__ size_t _res[3] = {(char*)&_test.view_vec - (char*)&_test, (char*)&_test.value - (char*)&_test, sizeof(_test)};
9   

Errors:
nvrtc: error: invalid value for --gpu-architecture (-arch)

header_of_structs.h:
1   struct _S_1bdca0bfccd39798
2   {
3       typedef _S_1bdca0bfccd39798 CurType;
4        view_vec;
5       float value;
6       template<class _T0>
7       __device__ inline auto operator()(const _T0& idx)
8       {
9       view_vec[idx]=(decltype(view_vec)::value_t)value;    }
10  };
11  

saxpy.cu:
1   #define DEVICE_ONLY
2   #include "cstdint"
3   #include "cfloat"
4   #include "cuComplex.h"
5   #include "built_in.h"
6   #include "header_of_structs.h"
7   
8   extern "C" __global__
9   void saxpy(size_t n, _S_1bdca0bfccd39798 func)
10  {
11      size_t tid =  threadIdx.x + blockIdx.x*blockDim.x;
12      if(tid>=n) return;
13      func(tid);
14  
15  }
16  

Errors:
nvrtc: error: invalid value for --gpu-architecture (-arch)

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/local/lib/python3.7/dist-packages/ThrustRTC/Transformations.py", line 4, in Fill
    check_i(native.n_fill(vec.m_cptr, value.m_cptr))
  File "/usr/local/lib/python3.7/dist-packages/ThrustRTC/Native.py", line 16, in check_i
    raise SystemError("An internal error happend")
SystemError: An internal error happend

[fynv]

What is the CUDA version and GPU type being used here?

In ThrustRTC, I use: cuDeviceGetAttribute(&major, CU_DEVICE_ATTRIBUTE_COMPUTE_CAPABILITY_MAJOR, cuDevice); to get the major compute capability (major is clamped to [2,7]). Then sprintf(opt, "--gpu-architecture=compute_%d0", major); is used to set the gpu-architecture. The above prcess seems to have caused the issue.

Not very sure yet how to fix this. Most likely, the arch compute_70 is not supported by the CUDA (nvrtc) being used here. A CUDA version above 10 should not have such issue,

[slayoo]

Thanks

 from numba import cuda
 cuda.detect()

gives

Found 1 CUDA devices
id 0            b'Tesla K80'                              [SUPPORTED]
                      compute capability: 3.7
                           pci device id: 4
                              pci bus id: 0
Summary:
    1/1 devices are supported

True

[slayoo]

and !nvcc --version gives:

nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2020 NVIDIA Corporation
Built on Mon_Oct_12_20:09:46_PDT_2020
Cuda compilation tools, release 11.1, V11.1.105
Build cuda_11.1.TC455_06.29190527_0

[fynv]

Ok. That is compute_30 hitting the lower-bound of CUDA 11.1. You need to down-grade your CUDA to 10.0 or lower, or upgrade your GPU to Maxwell or higher.

In a Kepler + CUDA 11.1 setup, basically any CUDA code that requires compilation won't work.

For ThrustRTC, there are 2 different cases where you'll hit a compilation problem: A. Volta GPU (or higher) + CUDA 8.0 or lower, where compute_70 hits the upper-bound of CUDA B. Kepler GPU (or lower) + CUDA 10.2 or higher, where compute_30 hits the lower bound of CUDA

[slayoo]

Thanks. There is no control over hardware in Colab. Will try getting non-default CUDA version... but it's tricky to ask users to do it every time...

Why is it working then with ThrustRTC 0.3.8?

Can we do any better in making this reported to the users by ThrustRTC?

[fynv]

I think it was "working" in 0.3.8 just because some checking was missing. It might give you some incorrect result silently back then.

[slayoo]

Confirming it works on Colab after downgrading CUDA. Let me then close this issue and open a new one re reporting the need to change CUDA version

[slayoo]

Downgrading CUDA make the short example above work indeed, but trying with the actual code I've earlier extracted the minimal reproducer I now get (with CUDA 10.0):

nvrtc: error: failed to load builtins for compute_30.

Any hints? Thanks

[fynv]

Try export LD_LIBRARY_PATH="/usr/local/cuda/lib64" It might be solved by this or it could be an incomplete support of an arch, which will be tricky..

[fynv]

Especially, if you downgraded CUDA by hack, you need to make sure that libnvrtc-builtins.so from CUDA 10 is within LD_LIBRARY_PATH, not the one from CUDA 11.

[slayoo]

It works out of the box with default Colab Cuda with ThrustRTC 0.3.15! Thank you !!!