Numerical kernel solver of the GEM-Selektor v.3 package for geochemical modelling. Just extended with an alternative Activity C API as the basis for a new Python API (based on Pybind11) on top of it, see xGEMS repository.

Main version use ThermoFun - a code for calculating the standard state thermodynamic properties of substances and reactions at a given temperature and pressure.

The code Implements the improved GEM IPM-3 algorithm with excellent mass balance precision and fast convergence to Gibbs energy minimum even in very complex non-ideal chemical systems with two-sided metastability constraints (learn more on GEMS3K web page).

The code is written in C/C . Using compiler directives, the GEMS3K code can be compiled as a standalone program e.g. 'gemcalc'; as a static or dynamic library for coupling with the mass transport simulator or another code; or as part of the GEM-Selektor v3 code together with GUI and databases.

Input: The standalone GEMS3K code needs to be initialized by reading a set of GEMS3K I/O files (since v.3.8.1, also a set of JSON documents) that can be exported from GEM-Selektor code for any chemical system (SysEq record) or from any GEM2MT task.

• Version: currently 4.4.0.

GEMS3K is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

GEMS3K is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with GEMS3K code. If not, see http://www.gnu.org/licenses/.

GEMS3K can be easily installed using Conda package manager. If you have Conda installed, first add the conda-forge channel by executing

#!bash
conda config --add channels conda-forge

install GEMS3K by executing the following command:

#!bash
conda install gems3k

Conda can be installed from Miniconda.

In your home directory, make a folder named e.g. ~/gitGEMS3 with a subfolder gitGEMS3/standalone.

Change into ~/gitGEMS3/standalone and clone this repository from https://bitbucket.org/gems4/gems3k.git using git, a preinstalled free git client SourceTree or SmartGit (the best way on Windows).

Alternatively on Mac OS X or linux or Windows10, open a terminal and type in the command line (do not forget a period) to download the actual "trunk" branch:

git clone https://bitbucket.org/gems4/gems3k.git . 

To switch to another branch (e.g. devEJDB), use a git client or open a terminal, cd to ~/gitGEMS3/standalone, and type in the command line

git checkout -b branches/devEJDB --track origin/branches/devEJDB
git pull origin branches/devEJDB

To switch back to trunk, type

git checkout trunk

• Install Dependencies by executing in ~/standalone$ (if not using Conda environment)

#!bash
sudo ./install-dependencies.sh

• If using conda environment (recommended) create and activate the gems3k environnement by executing in ~/standalone$:

conda devenv
conda activate GEMS3K

• Build GEMS3K library and examples The most common way to build GEMS3K on Linux or MacOS is using cmake (https://cmake.org/). Please, make sure that you have cmake installed in your system.

  To build GEMS3K and install it in your home directory or in the system directory (as in the example below), a typical sequence of commands can be executed in the terminal:

cd ~/gitGEMS3/standalone
mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX=/usr/local
make
sudo make install

The same will be done by executing the install.sh script instead (check that this file has executable status, if not, run a command "chmod x ./install.sh"):

cd ~/gitGEMS3/standalone
sudo ./install.sh

• Building and installing without ThermoFun library

cd ~/gitGEMS3/standalone
sudo ./install-dependencies.sh NO_THERMOFUN
sudo ./install_no_thermofun.sh

• For using qmake or QtCreator for building the GEMS3K chemical solver library and examples, please consult this web page: http://gems.web.psi.ch/GEMS3K/techinfo.htm

Since version 3.7.0, the GEMS3K "ipm.dat" files exported by earlier versions of GEM-Selektor may need a small modification: the "<ID_key> " needs to be entered at the beginning of an exported "ipm.dat file". This can be done using any plain-txt editor (TextEdit, nano, SublimeText, VScode).

Introducing the <ID_key> key was necessary to improve the GEMS3K I/O consistent use of the legacy key-value and JSON data formats. However, to ensure the readability of old GEMS3K file sets (exported from GEM-Selektor before version 3.7), we have made a workaround patch that skips the string after (missing) <ID_key>. This patch is available since the git commit "ffb5283" made on January 15, 2021.

Examples of the beginning of "ipm.dat" file valid since v.3.7.0:

• KeyValue format with comments:

#  GEMS3K v.3.8.1 c.0aa600e 
# Comments can be marked with # $ ; as the first character in the line
# IPM text input file for the internal GEM IPM-3 kernel data
# (should be read after the DCH file and before DBR files)

# ID key of the initial chemical system definition
<ID_key>  "Kaolinite G  pHtitrKaS   0    0       1       25      0   "

## (1) Flags that affect memory allocation
# PE: Flag for using electroneutrality condition in GEM IPM calculations (1 or 0)
<pa_PE>  1
# PV: Flag for the volume balance constraint (on Vol IC) for indifferent equilibria at P_Sat (0 or 1)
..........

• KeyValue format without comments:

<ID_key>  "Kaolinite G  pHtitrKaS   0    0       1       25      0   "
<pa_PE>  1
..........

• JSON format (available since version 3.8.1):

[
   {
      "set": "Kaolinite",
      "ipm": 
	  {
         "ID_key": "Kaolinite G  pHtitrKaS   0    0       1       25      0",
         "pa_PE": 1,
...........          

More on GEMS3K I/O API, latest KeyValue and JSON formats will be added here soon.

####TBD

• Summary of set up
• Configuration
• Dependencies
• Database configuration
• How to run tests
• Deployment instructions

• Writing tests
• Code review
• Other guidelines