Rose Stem Tutorial


Before proceeding you should already be familiar with the Rose Stem section.

Artist's Impression of Cassini entering Saturn orbit

This tutorial will walk you through creating a simple example of the Rose Stem testing system which will involve piloting a spaceship through space.

Getting Started

We will start the Rose Stem tutorial by setting up an FCM repository called SPACESHIP to store the code and test suite in.

Usually you would add a Rose Stem suite to an existing repository with the keyword already set up to test the accompanying source code. For the purposes of this tutorial we will create a new one.

Type the follow to create a temporary repository (you can safely delete it after finishing this tutorial):

mkdir -p ~/rose-tutorial
svnadmin create ~/rose-tutorial/spaceship_repos
(cd $(mktemp -d); mkdir -p trunk/src; svn import -m "" . file://$HOME/rose-tutorial/spaceship_repos)

We then need to link the project name SPACESHIP with this project. Creating the file and directory if they do not exist add the following line to the file $HOME/.metomi/fcm/keyword.cfg:

location{primary}[spaceship] = file:///home/user/rose-tutorial/spaceship_repos

Make sure the path on the right-hand side matches the location you specified in the svnadmin command.

Now you can checkout a working copy of your repository by typing:

mkdir -p ~/rose-tutorial/spaceship_working_copy
cd ~/rose-tutorial/spaceship_working_copy
fcm checkout fcm:spaceship_tr .

Finally populate your working copy by running (answering y to the prompt):

rose tutorial rose-stem .


Our Fortran program is spaceship_command.f90, which reads in an initial position and spaceship mass from one namelist, and a series of commands to apply thrust in three-dimensional space. It then uses Newtonian mechanics to calculate a final position.

You will find it in the src directory. Have a look at it and see what it does.

The spaceship app

Create a new Rose app called spaceship:

mkdir -p rose-stem/app/spaceship

Paste the following configuration into a rose-app.conf file within that directory:





thrust(1,:) =  1.0,  0.0, 0.0, 1.0,  0.0, -1.0, -1.0, 0.0, 0.0,  0.0
thrust(2,:) =  0.0, -2.0, 0.0, 1.0,  1.0,  0.5, -1.0, 1.5, 0.0, -1.0
thrust(3,:) =  0.0,  1.0, 0.0, 1.0, -1.0,  1.0, -1.5, 0.0, 0.0, -0.5

The fcm-make app

We now need to provide the instructions for fcm_make to build the Fortran executable.

Create a new app called fcm_make_spaceship with an empty rose-app.conf file.

Inside this app create a subdirectory called file and paste the following into the fcm-make.cfg file within that directory:

steps = build
build.source = $SOURCE_SPACESHIP/src{task} = link

The $SOURCE_SPACESHIP environment variable will be set using the Jinja2 variable of the same name which is provided by Rose Stem.

The suite.rc file

Next we will look at the rose-stem/suite.rc file.

The suite.rc file starts off with UTC mode = True, which you should already be familiar with. The next part is a Jinja2 block which links the group names the user can specify with the graph for that group. In this case, the group command_spaceship gives you the graph:

digraph Example { fcm_make_spaceship -> spaceship -> rose_ana_position }

This variable name_graphs is used later to generate the graph when the suite is run. The Jinja2 variable groups is next. This enables you to set shortcuts to a list of groups, in this case specifying all on the command line will run the tasks associated with both command_spaceship and fire_lasers.

The scheduling section contains the Jinja2 code to use the information we have already set to generate the graph based on what the user requested on the command line.

The runtime section should be familiar. Note, however, that the fcm_make_spaceship task sets the environment variable SOURCE_SPACESHIP from the Jinja2 variable of the same name. This is how the variables passed with --source on the command line are passed to fcm-make, which then uses these environment variables in its own configuration files.

The rose-suite.conf file

The suites associated with Rose Stem require a version number indicating the version of the rose stem command with which they are compatible. This is specified in the rose-suite.conf file, together with the default values of RUN_NAMES and SOURCE_SPACESHIP. Paste the following into your rose-suite.conf file:



Both of the Jinja2 variables will be overridden by the user when they execute rose stem on the command line.

The rose_ana_position app

The final component is a rose_ana app to test whether the position of our spaceship matches the correct output.

Create an app named rose_ana_position and paste the following into its rose-app.conf file.

[ana:grepper.FilePattern(Check X position at each timestep)]

[ana:grepper.FilePattern(Check Y position at each timestep)]

[ana:grepper.FilePattern(Check Z position at each timestep)]

This will check that the positions reported by the program match those within the known good output file.

Known Good Output

In the root of the working copy is a file called kgo.txt.

The known good output should be the result of a control run. Rose Ana will compare the answers from this file (obtained using the extract and comparison methods in the rose-app.conf file) with the results from the user’s code change.

Replace the /home/user/spaceship paths in the rose_ana_position app with the path to this file.

Adding the suite to version control

Before running the suite we need to make sure that all the files and directories we have created are known to the version control system.

Add all the new files you’ve created using fcm add -c (answer yes to the prompts).

Running the test suite

We should now be able to run the test suite. Simply type:

rose stem --group=command_spaceship

anywhere in your working copy (the --source argument defaults to . so it should automatically pick up your working copy as the source).


If your site uses a Cylc server, and your home directory is not shared with the Cylc server, you will need to add the option:


We use --group in preference to --task in this suite (both are synonymous) as we specify a group of tasks set up in the Jinja2 variable name_graphs.

A failing test

Now edit the file:


and change one of the thrusts, then rerun rose stem. You will find the rose_ana_position task fails, as the results have changed.

Try modifying the Fortran source code - for example, changing the direction in which thrust is applied (by changing the acceleration to be subtracted from the velocity rather than added). Again, rerun rose stem, and see the failure.

In this way, you can monitor whether the behaviour of code is changed by any of the code alterations you have made.

Further Exercises

If you wish, you can try extending the suite to include the fire_lasers group of tasks which was in the list of groups in the suite.rc file. Using the same technique as we’ve just demonstrated for piloting the spaceship, you should be able to aim and fire the ship’s weapons.

Automatic Options

It is possible to automatically add options to rose stem using the rose.conf[rose-stem]automatic-options variable in the Site And User Configuration file. This takes the syntax of key-value pairs on a single line, and is functionally equivalent to adding them using the -S option on the rose stem command line. For example:

automatic-options=GRAVITY=newtonian PLANET=jupiter

sets the variable GRAVITY to have the value newtonian, and PLANET to be jupiter. These can then be used in the suite.rc file as Jinja2 variables.