1>C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V120\BuildCustomizations\CUDA 9.0.targets(532,9): error : The CUDA Toolkit v9.0 directory '' does not exist.  Please verify the CUDA Toolkit is installed properly or define the CudaToolkitDir property to resolve this error.

解决方法：

右键 libcaffe 工程属性，找到 CUDA C/C++

设置 CUDA Tookit Custom Dir的值，指定CUDA的安装目录即可