Only load modules once per session in .bashrc

.bashrc

@@ -2,31 +2,36 @@
 # in /etc/profile, i.e. *before* ~/.profile!
 . ~/.env
 
-# setup modules
-# hierarchical module system: compiler → mpi → libraries
-#   Modules fftw-mpi and hdf5-mpi become available after loading a compiler module
-#   and an MPI library (impi). The available modules are determined by the
-#   compiler/MPI combination that was loaded (i.e. in this case, fftw-mpi is the
-#   version compiled with intel and impi).
-#   Currently, loading both compiler modules (gcc and intel) causes problems with the
-#   MODULEPATH that is set up by impi, so make sure to load another compiler only
-#   *after* impi is loaded!
-module load intel
-module load impi
-module load fftw-mpi
-module load hdf5-serial
-module load gsl
-module load pkg-config
-module load gcc  # load *after* intel and impi!
-module load clang
-module load datashare
-module load git
-#module load mathematica  # only available on login nodes
-#module load idl          # only available on login nodes
-module load anaconda
-module load julia
-module load gnuplot
-module load p7zip
+# setup modules; only execute once to prevent re-loading impi after loading gcc
+if [ -z "$_MODULES_LOADED" ]; then
+	# set variable to mark modules as loaded
+	_MODULES_LOADED=1
+	export _MODULES_LOADED
+	# hierarchical module system: compiler → mpi → libraries
+	#   Modules fftw-mpi and hdf5-mpi become available after loading a compiler module
+	#   and an MPI library (impi). The available modules are determined by the
+	#   compiler/MPI combination that was loaded (i.e. in this case, fftw-mpi is the
+	#   version compiled with intel and impi).
+	#   Currently, loading both compiler modules (gcc and intel) causes problems with
+	#   the MODULEPATH that is set up by impi, so make sure to load another compiler
+	#   only *after* impi is loaded!
+	module load intel
+	module load impi
+	module load fftw-mpi
+	module load hdf5-serial
+	module load gsl
+	module load pkg-config
+	module load gcc  # load *after* intel and impi!
+	module load clang
+	module load datashare
+	module load git
+	#module load mathematica  # only available on login nodes
+	#module load idl          # only available on login nodes
+	module load anaconda
+	module load julia
+	module load gnuplot
+	module load p7zip
+fi
 
 # if running interactively: set MPI variables; else stop
 # see https://www.mpcdf.mpg.de/services/computing/linux/Astrophysics