CPU_ONLY build: compiling the function Forward() gives error "undefined reference..."

[Nicola Fiorato]

I am a beginner with Caffe library.

I was just compiling and test code in this tutorial example: https://github.com/DeepLearningStudy/caffe/blob/master/examples/ex4_layer/main.cpp .

I have a CPU_ONLY build,  so compiling gives out error undefined reference to `void caffe::caffe_gpu_dot<double>(int, double const*, double const*, double*)' .

Issued by calling the function Forward().

In order to complete compilation I modified argmax layer code and put forward_cpu() as public function member.  

Does someone know why or a better solution?