Updated NERSC install instructions

Author: daurer

scripts/install_ptypy_env_at_nersc.md

@@ -1,3 +1,5 @@
+# Minimal installation
+
 First, clone the nersc conda env
 
 ```
@@ -16,32 +18,35 @@ Add additional packages that we need for ptypy with cupy
 conda install -c conda-forge pyfftw cupy
 ```
 
-Add additional packages that we need for ptypy with pycuda
+Install Ptypy
 ```
-conda install -c nvidia cuda-nvcc cuda-cudart-dev
-conda install -c conda-forge reikna pycuda
+git clone https://github.com/ptycho/ptypy.git
+pip install .
+
 ```
 
-Add additional packages for cufft
+Add kernel to user settings
 ```
-conda install -c nvidia libcufft-dev libcufft-static
-conda install -c conda-forge cmake>=3.8.0 pybind11
+python -m ipykernel install --user --name ptypy_env --display-name PtyPy
 ```
 
-Install Ptypy
-```
-git clone https://github.com/ptycho/ptypy.git
-pip install .
 
+## Optional installation adding pycuda and cufft
+
+Add additional packages that we need for ptypy with pycuda (optional, needed only for one extra tutorial)
+```
+conda install -c nvidia cuda-nvcc cuda-cudart-dev
+conda install -c conda-forge reikna pycuda
 ```
 
-Install cufft
+Add additional packages for cufft (optional)
 ```
-cd cufft
-pip install .
+conda install -c nvidia libcufft-dev libcufft-static
+conda install -c conda-forge cmake>=3.8.0 pybind11
 ```
 
-Add kernel to user settings
+Install cufft (optional)
 ```
-python -m ipykernel install --user --name ptypy_env --display-name PtyPy
+cd cufft
+pip install .
 ```