Assume you have downloaded the GSL software file gsl-1.15.tar.gz to directory /home/user/. Lets also assume that we are installing GSL at /home/user/GSL_install/.

1. Type cd /home/user.
2. Type tar -xzvf gsl-1.15.tar.gz This should create the directory : /home/user/gsl-1.15
3. Create local installation directory : mkdir /home/user/GSL_install. Note: The 'GSL_install' directory should be outside the '/home/user/gsl-1.15' directory.
4. Type cd /home/user/gsl-1.15.
5. You should do './configure --prefix=<path to your local installation>', i.e. in our example case, ./configure --prefix=/home/user/GSL_install/. This should complete without any errors to proceed to the next step.
6. Type make. This should complete without any errors to proceed to the next step.
7. Type make install. This should complete without any errors to proceed to the next step.
8. Check if installed correctly: cd /home/user/GSL_install/ and then ls.
   You should see the following directories : bin include lib share.
9. Type ls -al lib/. You should see several library files e.g. : libgsl.a, libgslcblas.a, libgsl.la etc.
10. Type export LD_LIBRARY_PATH=/home/user/GSL_install/lib/:$LD_LIBRARY_PATH (for bash shell)
11. Now you are ready to install and run FAST ( FAST Installation ).

If you have trouble installing GSL, check the INSTALL file and also see http://www.gnu.org/software/gsl/manual/html_node/Shared-Libraries.html. If you have installed GSL without any errors, you should have no trouble running FAST.

You should add the command in step 10 to your .bashrc / .bash_profile file located in your home directory, otherwise you will need to re-do the 'export' command as above everytime you log into the system.