Licallo/Software-Environment.md

 [[_TOC_]]
 
+## Software development environment
+
+The main software environment is based on the Intel solution for clusters (could be called "Cluster Edition"). It provides:
+
+ * The Intel compilers: icc (C), icpc (C++), ifort (Fortran) compilers.
+ * The Intel MPI environment.
+ * The Intel python environment.
+ * And other stuff.
+
+That environment relies on a Gnu runtime distribution for most the its runtime. Since the default Gnu runtime on our CentOS distribution is quite antique, we decided to rely on gcc 8.3 instead.
+This technicality is probably mostly relevant to C++ developers.
+ 
 ## The module system
 The software environment is managed through [lmod](https://lmod.readthedocs.io/en/latest/). Please have a look at the [User Guide](https://lmod.readthedocs.io/en/latest/010_user.html) if you are not already familiar with it.
 
@@ -7,16 +19,16 @@ The software environment is managed through [lmod](https://lmod.readthedocs.io/e
 
 Note that `module avail` does not display all the potentially available modules, only those available with the currently loaded modules.
 
-For example, let say the module `hdf5` depends on the module `intel-gnu8-runtime`, it will only appear once `intel-gnu8-runtime` is loaded:
+For example, let say the module `hdf5` depends on the module `intel-gnu8-runtime`, it will only appear once `intel-gnu8-runtime` is loaded[^1]:
 
 ```
 $ module purge
 $ module avail
 --------------------------------------------------- /opt/ohpc/pub/oca/modulefiles ---------------------------------------------------
-   intel-gnu8-runtime/19.0.5.281 
+   cmake/3.18.0    intel-gnu8-runtime/19.0.5.281    ne/3.3.0
 [...]
 ```
-We only got the "root" module. We need to load it to get the dependent ones:
+Here, We only see utility tool and the **intel-gnu8-runtime** module which provide the Intel based software environment. None the the libraries or tools based on that environment are shown until it's loaded:
 
 ```
 $ module load intel-gnu8-runtime
@@ -28,10 +40,30 @@ $ module avail
 [...]
 $
 ```
-You can use `module spider` to get the list of available modules.
 
-## The oca root module 
+You can use `module spider` to get the list of available modules regardless of what is already loaded and `module spider <modulename>` to get specific information on how to load a specific module.
+
+## Using python
+ 
+The supported python is the one provided with the Intel environment (**intel-gnu8-runtime**, which must be loaded first) and is provided through module **intelpython3**.
+
+
+```
+11:50:54 [alainm@castor ~]# module purge 
+11:51:01 [alainm@castor ~]# module load intel-gnu8-runtime
+11:51:11 [alainm@castor ~]# module load intelpython3 
+11:51:14 [alainm@castor ~]# python
+Python 3.6.9 |Intel Corporation| (default, Aug 18 2019, 19:47:51) 
+[GCC 4.8.2 20140120 (Red Hat 4.8.2-15)] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+Intel(R) Distribution for Python is brought to you by Intel Corporation.
+Please check out: https://software.intel.com/en-us/python-distribution
+>>> import numpy as np
+>>> np.zeros(10)
+array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0.])
+>>> ^D
+11:51:42 [alainm@castor ~]#
+``` 
 
-The supported module are dependent on the **oca** module, which should always be loaded.
 
-It is the root of a software environment built on Intel compilers using a fairly recent (8.x) Gnu runtime.
+[^1]: most libraries depend on the **intel-gnu8-runtime**, since it;s one we use to build them.