Q:

Where is nccl.h? 

Following Installing NCCL  I install NCCL:
sudo apt install libnccl2=2.4.2-1+cuda10.0 libnccl-dev=2.4.2-1+cuda10.0

But I can't find nccl.h. 
After I install NCCL, where is nccl.h? 

A:

This worked:
sudo dpkg-query -L libnccl-dev

