std::signbit<float> is not allowed

[anguyen8]

Install Caffe on Ubuntu 14.04 with Cuda 6.5 gives the following error.

/usr/local/cuda/bin/nvcc -ccbin=g++ -Xcompiler -fPIC -DNDEBUG -O2 -I/usr/local/include/python2.7 -I/usr/local/lib/python2.7/dist-packages/numpy/core/include -I/usr/local/include -Ibuild/src -I./src -I./include -I/usr/local/cuda/include -gencode arch=compute_20,code=sm_20 -gencode arch=compute_20,code=sm_21 -gencode arch=compute_30,code=sm_30 -gencode arch=compute_35,code=sm_35 -c src/caffe/util/math_functions.cu -o build/src/caffe/util/math_functions.cuo

Error 1:
src/caffe/util/math_functions.cu(140): error: calling a __host__ function("std::signbit<float> ") from a __global__ function("caffe::sgnbit_kernel<float> ") is not allowed

Error 2:
src/caffe/util/math_functions.cu(140): error: calling a __host__ function("std::signbit<double> ") from a __global__ function("caffe::sgnbit_kernel<double> ") is not allowed

2 errors detected in the compilation of "/tmp/tmpxft_00003368_00000000-12_math_functions.compute_35.cpp1.ii".
make: *** [build/src/caffe/util/math_functions.cuo] Error 2

The fix is here: http://stackoverflow.com/questions/28985551/caffe-installation-in-ubuntu-14-04

In caffe/include/caffe/util/math_functions.hpp

try changing

using std::signbit;
DEFINE_CAFFE_CPU_UNARY_FUNC(sgnbit, y[i] = signbit(x[i])); 

to

// using std::signbit;
DEFINE_CAFFE_CPU_UNARY_FUNC(sgnbit, y[i] = std::signbit(x[i]));