MEPT - Magnetospheric Ensemble Particle Tracing Model

Developer: Tom Gade

Acknowlegements: Thanks to Alex Gullickson who contributed to the multi-GPU functionality.

MEPT is a particle tracing simulation whose objective is to reproduce electron distributions under the influence of a number of physical phenomena (mirror force, quasi-static potential structures, Alfven waves, etc) gathered by FAST. It is written with C++/CUDA, and OpenMP.

Compatibility

MEPT runs on Windows and Linux. As it is dependent on CUDA, it requires an NVIDIA graphics card with up-to-date(-ish, at least) drivers, as well as the CUDA libraries installed. No other external dependencies for C++ exist. NOTE: This does not compile properly on the gpulab machines due to gcc and nvcc version issues. This is due to the use of the C++ filesystem library. As a result of using this, the code must be compiled via a version of gcc (Linux) that supports C++17 and the filesystem library. GCC 9 and up should work fine, but 10 is likely best. Additionally, CUDA 11.1 was used, although 10 and up should work fine.

Multi-GPU Execution

MEPT can be run on single or multiple GPU systems. Every CUDA capable GPU on the system will be utilized unless limited by the environment variable

```
CUDA_DEVICES_VISIBLE
```

On Windows, this can be set from powershell immediately prior to running the program. From the bin folder:

```
$Env:CUDA_VISIBLE_DEVICES="0,1"; ./MEPT
Note: the desired devices can be set through this flag.  e.g. using only 0 or only 1, etc
Observe the "" if using a comma to separate devices
```

On Linux, this is implemented by typing

```
CUDA_VISIBLE_DEVICES=0,1 ./MEPT
Note: the same note above applies
```

Dependencies

CUDA (see above - Compatibility)

Getting Started

1. Unpack Repository

Platform Agnostic

Unzip the zip file using your preferred zip file program.

2. Compile

Windows

Open the Visual Studio solution (MEPT/vs/MEPT.sln), ensure Release and x64 is selected, and in the toolbar click Build -> Build Solution.

Linux

chmod 777 ./configure
./configure
make

Note: gcc compatible with the -std=c++17 flag is required.

3. Run an example simulation

3a. Create a Particle Distribution

From a terminal in %WHEREVER%/MEPT

cd bin
./MEPT

3b. Run Simulation with Example Characteristics

(from MEPT)
cd bin
./MEPT

The program will create appropriate directories and save the data after execution in the folder _dataout. The characteristics of the simulation (BField model, EField model, etc) will be printed to the logfile contained within the data folder.