# Task needs to run twice **URL:** \ **Category:** Cylc Support\ **Created:** [April 29, 2025, 2:32pm UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160 "2025-04-29T14:32:37Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![sparonuz](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/sparonuz/32/495_2.png) [@sparonuz](https://cylc.discourse.group/u/sparonuz)\ **Post date:** [April 29, 2025, 2:32pm UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160/1 "2025-04-29T14:32:38Z")
Good afternoon, I have a workflow where I would like to run a task twice. It could be simplified as: ```auto [[graph]] # # Run just once at the initial cycle point # R1 = """ build_model => init_vars => copy_data_init """ # # Run at each cycle point # T00 = """ copy_data_init => init_vars => run_model """ ``` The task `init_vars` initializes some variables that I need both for copying the initialization data, and for running the model, and these variables depend on the cycle point, so they need to be recalculated each day at midnight. Of course I get an error > WorkflowConfigError: circular edges detected Is there a way of telling cylc that’s not a circular dependency? (I feel like this problem has a very easy solution, but somehow I can’t see it …) Thanks a lot for your help in advance, Stella ---
**Author:** ![oliver.sanders](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/oliver.sanders/32/110_2.png) [@oliver.sanders](https://cylc.discourse.group/u/oliver.sanders)\ **Post date:** [April 29, 2025, 3:27pm UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160/2 "2025-04-29T15:27:52Z")
Hi. `R1` means, “run once at the initial cycle point”. `T00` means, “run every day at midnight from the initial cycle point onwards”. In your case, I suspect that the initial cycle point is at midnight. As a result the midnight cycle contains both the `R1` and `T00` graphs, i.e: ```auto # R1 build_model => init_vars => copy_data_init # T00 copy_data_init => init_vars => run_model ``` Which is a cyclic graph because `init_vars` must run both before and after `copy_data_init`. * * * I think you probably want to exclude the initial cycle point from the `T00` graph like so: ```auto [scheduling] [[graph]] # Run just once at the initial cycle point R1 = """ build_model => init_vars => copy_data_init """ # Run every day at midnight (except in the first cycle) T00 ! R1 = """ copy_data_init => init_vars => run_model """ ``` Otherwise, if there is a requirement to run the same task twice within the same cycle, you can use an alias to copy the task like so: ```auto [scheduling] [[graph]] # Run just once at the initial cycle point R1 = """ build_model => init_vars_startup => copy_data_init """ # Run every day at midnight T00 = """ copy_data_init => init_vars => run_model """ [runtime] # define the task once [[INIT_VARS]] script = ... # but make two copies [[init_vars]] inherit = INIT_VARS [[init_vars_startup]] inherit = INIT_VARS ``` ---
**Author:** ![sparonuz](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/sparonuz/32/495_2.png) [@sparonuz](https://cylc.discourse.group/u/sparonuz)\ **Post date:** [April 30, 2025, 9:47am UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160/3 "2025-04-30T09:47:09Z")
Hi Olivier, If I understand correctly with the first solution, the “run\_model” will be executed starting from the second cycle point, and skipped at the initial one? Is this equivalent to put `! ^` ? This is not what I want, so the second solution is what I need. Thanks a lot for your help! Stella ---
**Author:** ![sparonuz](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/sparonuz/32/495_2.png) [@sparonuz](https://cylc.discourse.group/u/sparonuz)\ **Post date:** [April 30, 2025, 3:15pm UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160/4 "2025-04-30T15:15:08Z")
I was anyway trying to implement the first approach, but for some reason I can’t make it work … In reality my workflow does not start at midnight, I have a slightly more complicated recurrence ```auto [scheduling] initial cycle point = '20241111' final cycle point = '20241124' [[graph]] R1 = """ init_vars => copy_data_init """ R/2024-W01-1/P7D ! R1 = """ copy_data_init => init_vars => run_model """ ``` And with this I still get the circular graph error. I don’t understand, as soon as I change R/2024-W01-1/P7D → T00, it works. Is there any problem with the way I specify my recurrence expression? ---
**Author:** ![hilary.j.oliver](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/hilary.j.oliver/32/4_2.png) [@hilary.j.oliver](https://cylc.discourse.group/u/hilary.j.oliver)\ **Post date:** [April 30, 2025, 9:01pm UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160/5 "2025-04-30T21:01:48Z")
Hi @sparonuz I think the fact that _your recurrence expression starts before the initial cycle point of the workflow_ is causing some kind of a problem with recurrence processing. We’ll need to investigate that, but excluding the initial point specifically seems to work fine: `R/2024-W01-1/P7D ! ^` It also works if you start the P7D recurrence at the initial point, and exclude `R1`: `R/^/P7D ! R1 # or just "P7D ! R1"` (Then you have to make sure the initial cycle point falls on the right week day, but you’re already doing that for the R1 recurrence). Or figure out which week corresponds to your initial cycle point and start the recurrence there: `R/2024-W46-1/P7D ! R1` Or start it the following week so you don’t need the exclusion: `R/2024-W47-1/P7D` ---
**Author:** ![sparonuz](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/sparonuz/32/495_2.png) [@sparonuz](https://cylc.discourse.group/u/sparonuz)\ **Post date:** [May 5, 2025, 9:58am UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160/6 "2025-05-05T09:58:59Z")
Thanks @hilary.j.oliver ! You are right, as soon as I change my start point to ```auto [scheduling] initial cycle point = '20240101' final cycle point = '20240114' ``` It validates the worflow without errors. The problem is that we where searching a way of specifying a workflow running each Monday (or another specific day of the week), and this was the suggestion given in a [previous discussion](https://cylc.discourse.group/t/running-a-task-only-on-a-saturday/488/3). And we would like to have a recurrence expression independent from the initial cycle point (so, not change the week to 46 if the initial cycle point is the 11 November). Implementing your first workaround avoids the cycling graph error, but still the workflow doesn’t seems to run correctly. My worflow is now: ```auto [scheduling] initial cycle point = '20241111' final cycle point = '20241118' [[graph]] R1 = """ init_vars => copy_data_init """ R/2024-W01-1/P7D ! ^ = """ FAMBUILD[^]:succeed-all => init_vars => run_model """ [runtime] [[FAMBUILD]] [[FAMRUN]] [[init_vars]] platform = belenos_login script = """ echo "task init vars" """ [[copy_data_init]] platform = belenos_login script = """ echo "task copy_data_init" """ inherit = FAMBUILD [[run_model]] platform = belenos_login script = """ echo "task run_model" """ inherit = FAMRUN ``` And the graph shows the workflow as intended ![tmpjig1oqic](https://global.discourse-cdn.com/free1/uploads/cylc1/original/1X/98c582caf3881101b9f67660fc453f97e4bdb472.png) But when I play the workflow, first in the tui it shows a point that is not in the graph (20240101) ![Screenshot from 2025-05-05 11-47-17](https://global.discourse-cdn.com/free1/uploads/cylc1/original/1X/e787c4cc872f2eded905c49add0ae71516975615.png) And then the flow gets stuck at the FAMBUILD, it never triggers the 2024/11/18 run. ![Screenshot from 2025-05-05 11-48-38](https://global.discourse-cdn.com/free1/uploads/cylc1/original/1X/2ff1c5df6520af07508d51c9de8773ddd1326b43.png) Am I using Families in the wrong way?Or is still the same problem as before (i.e. the recurrence expression starts before the 1st cycle point)? Many thanks in advance for your help! Best, Stella ---
**Author:** ![hilary.j.oliver](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/hilary.j.oliver/32/4_2.png) [@hilary.j.oliver](https://cylc.discourse.group/u/hilary.j.oliver)\ **Post date:** [May 5, 2025, 10:53am UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160/7 "2025-05-05T10:53:55Z")
Hi Stella, A quick test shows the problem occurs even if you don’t use the family name in the graph, so it’s not that. The initial cycle point defines the start of the graph, so it wouldn’t be unreasonable for dependence on (non-existent) tasks prior to that to cause a stall. But Cylc is supposed to ignore pre-initial-point tasks as a convenience, to make writing the start of the graph easier, so it should work. Your example runs fine so long as the recurrence start point is `>=` initial point. So until we figure out what’s happening here, I think you’ll have to do that. > And we would like to have a recurrence expression independent from the initial cycle point (so, not change the week to 46 if the initial cycle point is the 11 November). Is there some reason why you can’t just do this: ```auto R/^/P7D ! ^ ``` This requires making sure that the initial cycle point is the first day of a week, but you have to do that for the `R1` expression anyway. ---
**Author:** ![sparonuz](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/sparonuz/32/495_2.png) [@sparonuz](https://cylc.discourse.group/u/sparonuz)\ **Post date:** [May 5, 2025, 3:28pm UTC](https://cylc.discourse.group/t/task-needs-to-run-twice/1160/8 "2025-05-05T15:28:02Z")
Hi @hilary.j.oliver Yes, you’re right, I will need to specify that anyway, so I can simplify my recurrence expression! Thanks a lot, Stella