support cuda 10.1

[rongou]

Doesn't quite work yet, I'm getting compilations errors:

/home/rou/src/xgboost/src/common/host_device_vector.cu: In instantiation of ‘void xgboost::HostDeviceVectorImpl<T>::DeviceShard::Init(xgboost::HostDeviceVectorImpl<T>*, int) [with T = long unsigned int]’:
/home/rou/src/xgboost/src/common/host_device_vector.cu:205:1:   required from ‘xgboost::HostDeviceVectorImpl<T>::InitShards()::<lambda(int, xgboost::HostDeviceVectorImpl<T>::DeviceShard&)> [with T = long unsigned int]’
/home/rou/src/xgboost/src/common/host_device_vector.cu:205:13:   required from ‘struct xgboost::HostDeviceVectorImpl<T>::InitShards() [with T = long unsigned int]::<lambda(int, struct xgboost::HostDeviceVectorImpl<long unsigned int>::DeviceShard&)>’
/home/rou/src/xgboost/src/common/host_device_vector.cu:204:23:   required from ‘void xgboost::HostDeviceVectorImpl<T>::InitShards() [with T = long unsigned int]’
/home/rou/src/xgboost/src/common/host_device_vector.cu:171:11:   required from ‘xgboost::HostDeviceVectorImpl<T>::HostDeviceVectorImpl(size_t, T, xgboost::GPUDistribution) [with T = long unsigned int; size_t = long unsigned int]’
/home/rou/src/xgboost/src/common/host_device_vector.cu:430:12:   required from ‘xgboost::HostDeviceVector<T>::HostDeviceVector(size_t, T, xgboost::GPUDistribution) [with T = long unsigned int; size_t = long unsigned int]’
/home/rou/src/xgboost/include/xgboost/data.h:186:14:   required from here
/home/rou/src/xgboost/src/common/host_device_vector.cu:56:16: error: cannot call member function ‘size_t xgboost::HostDeviceVectorImpl<T>::Size() const [with T = long unsigned int; size_t = long unsigned int]’ without object
       LazyResize(vec_->Size());
            ~~~~^~

[rongou]

The error is similar to protocolbuffers/protobuf#5805 and tensorflow/tensorflow#26155.

[RAMitchell]

Can you please add a new entry to the Jenkinsfile build matrix for cuda 10.1.

I think we can also remove the second entry from the build matrix, we should have sufficient coverage without it and it will speed up CI:

def buildMatrix = [
    [ "enabled": true,  "os" : "linux", "withGpu": true, "withNccl": true,  "withOmp": true, "pythonVersion": "2.7", "cudaVersion": "9.2", "multiGpu": true],
    [ "enabled": true,  "os" : "linux", "withGpu": true, "withNccl": true,  "withOmp": true, "pythonVersion": "2.7", "cudaVersion": "9.2" ],
    [ "enabled": true,  "os" : "linux", "withGpu": true, "withNccl": true,  "withOmp": true, "pythonVersion": "2.7", "cudaVersion": "8.0" ],
    [ "enabled": true,  "os" : "linux", "withGpu": true, "withNccl": false, "withOmp": true, "pythonVersion": "2.7", "cudaVersion": "8.0" ],
]

EDIT: Looks like there are no cuda 10.1 images yet (https://hub.docker.com/r/nvidia/cuda/). Maybe we can track down who maintains these.

[rongou]

Thought this was a compiler bug, I built gcc 8.3 from source, but still getting the same error.

[rongou]

Wow, it is a compiler bug. Got everything built under gcc 6.

[rongou]

@RAMitchell added 10.1 to the build matrix.

This should work now as long as we stick with gcc 6.

[trivialfis]

@rongou That's problematic. We might need to workaround that. Is it possible to file an issue at GCC with host code only?

[rongou]

Only partially fixes #4220 :(

[hcho3]

Wait, is 10.1 container available already?

[rongou]

@hcho3 yeah just got pushed to docker hub.

@trivialfis agreed. Maybe we should be less ambitious and stick with cuda 10.0 for now. Let me try to figure out if I can reproduce the bug easily.

[rongou]

Hmm, maybe it's actually a cuda sdk bug. In the generated host_device_vector.cudafe1.cpp, that line is changed to LazyResize(Size());, which is obviously incorrect.

[trivialfis]

@rongou Anyway I worked around it by de-referencing the pointer first:

(*vec_).Size();

[rongou]

@trivialfis cool, that's a good workaround for now. I made the change and added a TODO.

[codecov-io]

Codecov Report

Merging #4223 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4223      +/-   ##
==========================================
- Coverage   67.28%   67.27%   -0.01%     
==========================================
  Files         132      132              
  Lines       12219    12220       +1     
==========================================
  Hits         8221     8221              
- Misses       3998     3999       +1

Impacted Files	Coverage Δ
src/tree/updater_colmaker.cc	39.6% <0%> (-0.08%)	⬇️

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