# Run atlas¶

This document will tell you how to start running atlas after you have done Download and Install.

This video on running the atlas software covers some of the same material in this section.

## Get atlas running¶

Let’s say you’ve compiled the software in a directory atlasofliegroups. Use your terminal to navigate into that directory. It should contain the executable file atlas. To see this do:

file atlas


and you should see something like (of course details will differ):

atlas: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked,
interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=db51b2603a2949cfa75646963f81c18343dfb993,
for GNU/Linux 3.2.0, not stripped


The minimal way to test that atlas is has been installed correctly is to give the command:

./atlas


(depending on your environment the ./ might not be necessary).

You should see see something like this:

This is 'atlas' (version 1.1, axis language version 1.0),
the Atlas of Lie Groups and Representations interpreter,
compiled on Dec 30 2021 at 16:01:25.   http://www.liegroups.org/
atlas>


Assuming this works go to the next section to load scripts.

The software relies on a large set of auxiliary files in the directory atlasofliegroups/atlas-scripts, with the suffix .at (or .ax). Generally you want to load all of these, by loading the single file all.at.

Assuming you’ve run make install (see After compiling) then the command atlas will run the software, and load all.at, and therefore load all of the scripts.

Alternatively you can launch atlas and tell it where to find the scripts. Here are few examples.

We recommend creating a directory atlasofliegroups/my_files, and always starting atlas from there. Assuming you’ve run make install, you can do:

cd atlasofliegroups
mkdir my_files
cd my_files
atlas


This will read the necessary files from the directory atlasofliegroups/atlas-scripts, and any files you write to will be in atlasofliegroups/my_files. Another possibility (which doesn’t require make install is:

cd atlasofliegroups
mkdir my_files
cd my_files
../atlas --path=../atlas-scripts all.at


Alternatively go to thedirectory in which you built the software and run atlas from there:

cd atlasofliegroups
./atlas --path=atlas-scripts all.at


The path argument tells atlas where to find the scripts, and all.at says to load most of the scripts (possibly excluding a few which are under development).

Another option is to run atlas from the atlas-scripts directory, in which case it doesn’t need the path:

cd atlasofliegroups/atlas-scripts
../atlas all.at


To test if the scripts are loaded do:

atlas> set G=SL(2,R)


and you should see:

Variable G: RealForm
atlas> G
Value: connected split real group with Lie algebra 'sl(2,R)'


You can also load scripts from within atlas, for example:

./atlas --path=atlas-scripts
<basic.at


The symbol “<” means read a file.

To check if readline (command completion, recalling previous commands, etc.) is working, hit TAB on your keyboard twice. You should see something like:

atlas>
Display all 902 possibilities? (y or n)


This indicates that command completion is working. Now do a few simple commands:

atlas> 1+1
Value: 2
atlas> set G=SL(2,R)
Identifier G: RealForm
atlas> print_block(trivial (G))
Parameter defines element 2 of the following block:
0:  0  [i1]  1   (2,*)  *(x=0,lam=rho+  [0], nu=  [0]/1)  e
1:  0  [i1]  0   (2,*)  *(x=1,lam=rho+  [0], nu=  [0]/1)  e
2:  1  [r1]  2   (0,1)  *(x=2,lam=rho+  [0], nu=  [1]/1)  1^e


Congratulations! Now you have atlas working on your machine! Proceed to Tutorial for some examples of what you can do with atlas.

## Quit atlas¶

Just type quit` :)