Notebook-based gsmo module that computes the Hailstone sequence:

This module also demonstrates several features of gsmo modules:

• state-propagation across runs
• early-stopping
• custom commit-messages

The file value will hold an integer; initialize it to 6 if it doesn't exist:

INITIAL_STATE = 6

from pathlib import Path
value_path = Path('value')
if value_path.exists():
    with value_path.open('r') as f:
        value = int(f.read().strip())
        print('Loaded previous value: %d' % value)
else:
    value = INITIAL_STATE
    print('Set default value: %d' % value)

if value == 1:
    raise Exception('OK: value is 1; exiting early')

prev_value = value
if value % 2 == 0:
    value = value / 2
else:
    value = 3*value + 1
print('New value: %d' % value)

The _STATE file in this module is read by the gsmo runner, and contains contents:

value

This tells the runner machinery that any changes to the path value should be included in the Git commit representing a run (which is committed in a clone of the module that lives under runs/ in the module directory).

Additionally, the runner will merge changes to the value file upstream into the outer repo (which subsequent runs are cloned from; note this is not true of other files generated by runs and committed in the runs/ clone, like the logs/{out,err} and SUCCESS/FAILURE files).

with value_path.open('w') as f:
    f.write('%d\n' % value)

Finally, by writing to the _MSG, we can tell gsmo what the commit message for this run should be:

commit_msg_path = Path('_MSG')
with commit_msg_path.open('w') as f:
    f.write('%d → %d\n' % (prev_value, value))