README.md

# CORSIKA 8 Framework for Particle Cascades in Astroparticle Physics 

The purpose of CORSIKA is to simulate any particle cascades in
astroparticle physics or astrophysical context. A lot of emphasis is
put on modularity, flexibility, completeness, validation and
correctness. To boost computational efficiency different techniques
are provided, like thinning or cascade equations. The aim is that
CORSIKA remains the most comprehensive framework for simulating
particle cascades with stochastic and continuous processes.

The software makes extensive use of static design patterns and
compiler optimization. Thus, the most fundamental configuration
decision of the user must be performed at compile time. At run time
model parameters can still be changed.

CORSIKA 8 is by default released under the GPLv3 license. See [license
file](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/LICENSE)
which is part of every release and the source code.

If you use, or want to refer to, CORSIKA 8 please cite ["Towards a Next
Generation of CORSIKA: A Framework for the Simulation of Particle
Cascades in Astroparticle Physics", Comput.Softw.Big Sci. 3 (2019)
2](https://doi.org/10.1007/s41781-018-0013-0). We kindly ask (and
require) any relevant improvement or addition to be offered or
contributed to the main CORSIKA 8 repository for the benefit of the
whole community.

When you plan to contribute to CORSIKA 8 check the guidelines outlined here:
[coding
guidelines](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/CONTRIBUTING.md). Code
that fails the review by the CORSIKA author group must be improved
before it can be merged in the official code base. After your code has
been accepted and merged, you become a contributor of the CORSIKA 8
project (code author). 

IMPORTANT: Before you contribute, you need to read and agree to the
[collaboration
agreement](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/COLLABORATION_AGREEMENT.md). The agreement can be discussed, and eventually improved.

We also want to point you to the [MCnet
guidelines](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/MCNET_GUIDELINES), which are very useful also for us.


## Get in contact
  * Join our chat threads using Mattermost via this [invite link](https://mattermost.hzdr.de/signup_user_complete/?id=xtdd8jyt6trbiezt71gaz3z4ge&md=link&sbr=su). Click the `GitLab` button, then `Sign in with Helmholtz ID`. You will be able to make an account by either finding your institution, or using your e.g. ORCID, GitHub, or Google account.

  * Connect to https://gitlab.iap.kit.edu, register yourself and join the "Air Shower Physics" group. Write to us on Mattermost (in the User Questions channel), or directly contact one of the [steering comittee members](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/-/wikis/Steering-Committee) in case there are problems with that. 
  * Connect to corsika-devel@lists.kit.edu (self-register at
    https://www.lists.kit.edu/sympa/subscribe/corsika-devel) to get in
    touch with the project.


## Installation

CORSIKA 8 is tested regularly at least on `gcc11.0.0` and `clang-14.0.0`. 

### Prerequisites

You will also need:

- Python 3 (supported versions are Python >= 3.6), with pip
- conan (via pip)
- cmake > 3.4
- git
- g++, gfortran, binutils, make
- optional: FLUKA (see below)


On a bare Ubuntu 20.04, just add:
``` shell
sudo apt-get install python3 python3-pip cmake g++ gfortran git doxygen graphviz
```

On a bare CentOS 7 install python3, pip3 (pip from python3) and cmake3. Any of the devtools 7, 8, 9 should work (at least). 
Also initialize devtools, before building CORSIKA 8:
``` shell
source /opt/rh/devtoolset-9/enable
```

### Creating a virtual environment and Conan

It is recommended that you install CORSIKA 8 and its dependencies within a python3 virtual environment.
To do so, you can run the following.
``` shell
# Create the environment using your native python3 binary
python3 -m venv /path/to/new/virtual/environment/corsika-8
# Load the environment (should be run each time you open a new terminal)
source /path/to/new/virtual/environment/corsika-8/bin/activate

```

You will need to load the environment each time that you open a new terminal.

CORSIKA 8 uses the [conan](https://conan.io/) package manager to
manage our dependencies. Currently, version 1.57.0 or higher is required.  
**Note**: if you are NOT using a virtual environment, you may want to use the `pip install --user` flag.

``` shell
pip install conan~=1.57.0
```

### Compiling

Once Conan is installed, follow these steps to download and install CORSIKA 8:

``` shell
cd ./top/directory/for/corsika/installation
git clone --recursive https://gitlab.iap.kit.edu/AirShowerPhysics/corsika.git
# Or for https: git clone --recursive git@gitlab.iap.kit.edu:AirShowerPhysics/corsika.git
mkdir corsika-build
cd corsika-build
../corsika/conan-install.sh
cmake ../corsika -DCMAKE_BUILD_TYPE="RelWithDebInfo" -DCMAKE_INSTALL_PREFIX=../corsika-install
make -j4  #The number should match the number of available cores on your machine
make install
```

### FLUKA support

For legal reasons we do not distribute/bundle FLUKA together with CORSIKA 8.
If you want to use FLUKA as low-energy hadronic interaction model, you have to download
it separately from (http://www.fluka.org/), which requires registering there as FLUKA user.
The following should be done *before* compiling CORSIKA 8:

 1. Note your system's version of gcc (`gcc --version`) and glibc (`ldd --version`)
 2. Download the FLUKA __binary__, ensuring that it matches the versions you found above
 3. Download the FLUKA __data file__ (will be named something similar to __fluka20xy.z-data.tar.gz__).
 4. Un-tar the files that you downloaded using `tar -xf <filename>`
 5. Set environmental variables `export FLUFOR=gfortran` and `export FLUPRO=<path to where you unzipped the files>`. Note that the `FLUPRO` directory should contain __libflukahp.a__. Both of these variables will have to be set every time you open a new terminal.
 6. Go to the `FLUPRO` directory and run `make`. This will compile an exe, __flukahp__, in your current directory.
 7. Follow the normal steps to compile CORSIKA 8 (see above). However, during the `cmake` step, append the additional flag `-DWITH_FLUKA=ON`

When you install CORSIKA 8, you should see a message during the __cmake__ step indicating the FLUKA was correctly found.

``` shell
libflukahp.a found in directory <some location here> via FLUPRO environment variable
FLUKA support is enabled.
```


## Installation (using docker containers)

There are docker containers prepared that bring all the environment and packages you need to run CORSIKA. See [docker hub](https://hub.docker.com/repository/docker/corsika/devel) for a complete overview. 

### Prerequisites

You only need docker, e.g. on Ubunut: `sudo apt-get install docker` and of course root access.

### Compiling

Follow these steps to download and install CORSIKA 8, master development version
```shell
cd ./top/directory/for/corsika/installation
git clone --recursive https://gitlab.iap.kit.edu/AirShowerPhysics/corsika.git
sudo docker run -v $PWD:/corsika -it corsika/devel:clang-8 /bin/bash
mkdir build
cd build
../corsika/conan-install.sh
cmake ../corsika -DCMAKE_INSTALL_PREFIX=../corsika-install
make -j4  #The number should match the number of available cores on your machine
make install
```

## Runing Unit Tests

To run the unit tests, do the following.

```shell
cd ./corsika-build
ctest
```

## Running applications and examples

### Standard applications

Applications for standard use-cases are located in the `applications` directory.
These are example scripts that can be used directly or slightly modified for your use case.
See [applications/README.md] for more.
The applications are compiled automatically after running `make` and will appear your `corsika-build/bin` directory.
After running `make install` the binaries will also be copied into your `corsika-install/bin` directory as well.


For example, from inside your `corsika-install/bin` directory, run 
```shell
c8_air_shower --pdg 2212 -E 1e5 -f my_shower
```
This will run a vertical 100 TeV proton shower and will create and put the output into `./my_shower`.


### Building the examples

Unlike the applications, the examples must be compiled as a second step.
From your top corsika directory, (the one that includes `corsika-build` and `corsika-install`) run
```shell
cmake -Dcorsika_DIR=$PWD/corsika-build -S ./corsika/examples -B ./corsika-build-examples
cd corsika-build-examples
make -j4 #The number should match the number of available cores on your machine
```

You can run the examples by using the binaries in `corsika-build-examples/bin/`.
For example:
```shell
corsika-build-examples/bin/known_particles
```
This will print out all of the particles that are known by CORSIKA.


### Generating doxygen documentation

To generate the documentation, you need doxygen and graphviz. If you work with 
the docker corsika/devel containers this is already included. 
Otherwise, e.g. on Ubuntu 18.04, do:
```shell
sudo apt-get install doxygen graphviz
```
Switch to the corsika build directory and do
```shell
make docs
make install
```
open with firefox:
```shell
firefox ../corsika-install/share/corsika/doc/html/index.html
```