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+# Guide to installing and running GRAS 
+### by Sai Krishanth Pulikesi Mannan (saikrishanth@arizona.edu)
+
+*This has been tested on a 2021 MacBook Pro running macOS 12.6, a general install guide is available at https://spitfire.estec.esa.int/trac/GRAS/wiki/GRAS/GRAS-05-02-01/InstallationGuide
+
+## Installing:
+
+1. Start by installing Geant4 (official installation documentation here: https://geant4-userdoc.web.cern.ch/UsersGuides/InstallationGuide/html/index.html):
+
+Software prerequisites:
+
+a. C++ compiler and standard library supporting the C++17 standard. This includes gcc 8 or higher on Linux, clang 12 or higher on macOS, and visual studio 19 or higher on Windows.
+b. cmake (download from the website or brew on macOS)
+c. xerces-c (download from the website or brew on macOS)
+
+The latest version is 11.0.3, available at https://geant4.web.cern.ch/support/download. However, GRAS does not appear to be compatible with this version on my computer and I found success running 10.7 instead, available at https://geant4.web.cern.ch/support/download_archive. Download the gzip file and untar it. Move the newly untarred file to an appropriate installation location, henceforth called `/path/to/geant4.10.07.p04`. Navigate to `/path/to/` and create a new directory called `geant4.10.07.p04-build` and change into this directory. Now type:
+
+```
+cmake -DCMAKE_INSTALL_PREFIX=/path/to/geant4.10.07.p04-install -DGEANT4_INSTALL_DATA=ON -DGEANT4_USE_GDML=ON /path/to/geant4.10.07.p04
+```
+
+If successful, you should have an output like `-- Build files have been written to: /path/to/geant4.10.07.p04-build`. 
+
+Now type (N is the number of cores you want to simultaneously use for the install):
+
+```
+make -jN
+```
+
+After this type:
+
+```
+make install
+```
+
+This will install geant4 on your computer. After this, navigate to `/path/to/geant4.10.07.p04-install/bin` and type:
+
+```
+source geant4.sh
+```
+
+2. Now we install GRAS, available from: https://essr.esa.int/project/gras-geant4-radiation-analysis-for-space/link/125
+
+First, download the gzip file and untar it. You can then move it to `/path/to/gras-05-02-01`. Navigate to `/path/to/` and make a directory named `gras-05-02-01-build` and change into this directory. Now type:
+
+```
+cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr/local/gras/GRAS-05-02-01 -DGRAS_INSTALL_PREFIX=/usr/local/gras/GRAS-05-02-01 -DSTATIC_BUILD=OFF -DWITH_GEANT4_UIVIS=ON -DWITH_MESHING_ANALYSIS=ON -DWITH_ROOT=OFF -DWITH_ZSTR=OFF /path/to/gras-05-02-01
+```
+
+If successful, you should have an output like `-- Build files have been written to: /path/to/gras-05-02-01-build`. 
+
+Now type (N is the number of cores you want to simultaneously use for the install):
+
+```
+make -jN
+```
+
+After this type (you might have to use sudo, but you can get around that by setting `CMAKE_INSTALL_PREFIX = /path/to/gras-05-02-01-install`, and not including `-DGRAS_INSTALL_PREFIX=/usr/local/gras/GRAS-05-02-01` in the above command):
+
+```
+make install
+```
+
+This will install GRAS on your computer. After this type:
+
+```
+source /usr/local/gras/GRAS-05-02-01/bin/gras-env.sh
+```
+
+3. Some troubleshooting:
+
+You might have the following error while running GRAS:
+
+```
+dyld[53191]: Library not loaded: '@rpath/libG4Tree.dylib'
+Referenced from: '/usr/local/gras/GRAS-05-02-01/bin/gras'
+Reason: tried: '/usr/local/gras/GRAS-05-02-01/lib//libG4Tree.dylib' (no such file), '/usr/local/lib/libG4Tree.dylib' (no such file), '/usr/lib/libG4Tree.dylib' (no such file)
+Abort trap: 6
+```
+
+In which case, navigate to `/path/to/geant4.10.07.p04-install/lib` and copy the lib files present into `/path/to/gras-05-02-01-install/lib`, and then type:
+
+```
+export DYLD_LIBRARY_PATH='/path/to/gras-05-02-01-build/lib'
+```
+
+Now GRAS should run.
+
+## Using GRAS (coming soon...)
+
+For questions, comments, and suggestions, contact saikrishanth@arizona.edu