Basic Cycling§

In this section we will look at how to write cycling (repeating) workflows.

Repeating Workflows§

To make a workflow repeat we must tell Cylc three things:

Repeating Workflows§

 [scheduling]
+    cycling mode = integer
+    initial cycle point = 1
     [[dependencies]]
+        [[[P1]]]
             graph = """
                 purchase_ingredients => make_dough
                 pre_heat_oven & make_dough => bake_bread => sell_bread & clean_oven
             """

Repeating Workflows§

Inter-Cycle Dependencies§

 [scheduling]
     cycling mode = integer
     initial cycle point = 1
     [[dependencies]]
         [[[P1]]]
             graph = """
                 purchase_ingredients => make_dough
                 pre_heat_oven & make_dough => bake_bread => sell_bread & clean_oven
+                clean_oven[-P1] => pre_heat_oven
             """

Inter-Cycle Dependencies§

 [scheduling]
     cycling mode = integer
     initial cycle point = 1
     [[dependencies]]
         [[[P1]]]
             graph = """
                 purchase_ingredients => make_dough
                 pre_heat_oven & make_dough => bake_bread => sell_bread & clean_oven
                 clean_oven[-P1] => pre_heat_oven
+                sell_bread[-P2] => purchase_ingredients
             """

Inter-Cycle Dependencies§

Note

The [-P2] suffix is used to reference a task two cycles before. For the first two cycles this doesn’t make sense as there was no cycle two cycles before, so this dependency will be ignored.

Any inter-cycle dependencies stretching back to before the initial cycle point will be ignored.

Recurrence Sections§

[scheduling]
    cycling mode = integer
    initial cycle point = 1
    [[dependencies]]
        [[[P1]]]  # Repeat every cycle.
            graph = foo
        [[[P2]]]  # Repeat every second cycle.
            graph = bar
        [[[P3]]]  # Repeat every third cycle.
            graph = baz

Recurrence Sections§

5/P3: Repeat every third cycle starting from cycle number 5.
+P5/P3: Repeat every third cycle starting 5 cycles after the initial cycle point.

Recurrence Sections§

In this practical we will take the suite we wrote in the previous section and turn it into a cycling suite.

Next section: Date-Time Cycling

Practical

In this practical we will take the suite we wrote in the previous section and turn it into a cycling suite.

If you have not completed the previous practical use the following code for your suite.rc file.

[scheduling]
    [[dependencies]]
        graph = """
            foo & pub => bar => baz & wop
            baz => qux
        """

Create a new suite.

Within your ~/cylc-run/ directory create a new (sub-)directory called integer-cycling and move into it:
```
mkdir ~/cylc-run/integer-cycling
cd ~/cylc-run/integer-cycling
```
Copy the above code into a suite.rc file in that directory.

Make the suite cycle.

Add in the following lines.

 [scheduling]
+    cycling mode = integer
+    initial cycle point = 1
     [[dependencies]]
+        [[[P1]]]
             graph = """
                 foo & pub => bar => baz & wop
                 baz => qux
             """

Visualise the suite.

Try visualising the suite using cylc graph.
```
cylc graph .
```
Tip

You can get Cylc graph to draw dotted boxes around the cycles by clicking the “Organise by cycle point” button on the toolbar:
Tip

By default cylc graph displays the first three cycles of a suite. You can tell cylc graph to visualise the cycles between two points by providing them as arguments, for instance the following example would show all cycles between 1 and 5 (inclusive):
```
cylc graph . 1 5 &
```

Add another recurrence.

Suppose we wanted the qux task to run every other cycle as opposed to every cycle. We can do this by adding another recurrence.

Make the following changes to your suite.rc file.

 [scheduling]
     cycling mode = integer
     initial cycle point = 1
     [[dependencies]]
         [[[P1]]]
             graph = """
                 foo & pub => bar => baz & wop
-                baz => qux
             """
+        [[[P2]]]
+            graph = """
+                baz => qux
+            """

Use cylc graph to see the effect this has on the workflow.

Inter-cycle dependencies.

Next we need to add some inter-cycle dependencies. We are going to add three inter-cycle dependencies:
1. Between wop from the previous cycle and pub.
2. Between baz from the previous cycle and foo every odd cycle.
3. Between qux from the previous cycle and foo every even cycle.
Have a go at adding inter-cycle dependencies to your suite.rc file to make your workflow match the diagram below.
Hint
- P2 means every odd cycle.
- 2/P2 means every even cycle.
Solution
```
[scheduling]
    cycling mode = integer
    initial cycle point = 1
    [[dependencies]]
        [[[P1]]]
            graph = """
                foo & pub => bar => baz & wop
                wop[-P1] => pub  # (1)
            """
        [[[P2]]]
            graph = """
                baz => qux
                baz[-P1] => foo  # (2)
            """
        [[[2/P2]]]
            graph = """
                qux[-P1] => foo  # (3)
            """
```