<@ULVA73B9P> It seems like the paralleism is not a...
# marvin-in-the-wild
m
@Marvin It seems like the paralleism is not a default behaviour - since the
flows
are dynamic by default => no DAGs => no way to paralleize automatically and everything needs to be explicitly paralleized. Even if my
flow
is embarrassingly parallel, nothing gets paralleized automatically. The only way to achieve that is to use
<task>.map
, right? https://docs-3.prefect.io/3.0rc/develop/task-runners#mapping-over-iterables or am I missing something?
m
You're correct that parallelization is not automatic in Prefect. Tasks will run sequentially unless you explicitly use mechanisms such as task.map or compatible task runners. 1. Mapping: Using
task.map
is a way to parallelize tasks across multiple iterations of data. Example:
Copy code
@task
def process_data(x):
    return x * 2

@flow
def my_flow():
    result = process_data.map([1, 2, 3])
(source: https://docs.prefect.io/latest/faq/) 2. Concurrency and Parallelism: Prefect supports creating concurrency limits and also has task runners specifically designed for parallelism, such as the
ConcurrentTaskRunner
,
DaskTaskRunner
, and
RayTaskRunner
. (source: https://docs.prefect.io/latest/concepts/task-runners/) These features must be configured explicitly to achieve the desired parallel execution.
You are correct that in Prefect, parallelization is not a default behavior and needs to be explicitly defined. Here are the key points about parallelizing tasks in Prefect: 1. Dynamic Flows: Since flows are dynamic, there isn't a predefined DAG, so tasks won't automatically parallelize. 2. Task Mapping: Using
task.map
is a common way to parallelize tasks explicitly. This allows you to run the same task across multiple inputs in parallel. 3. Task Runners: Additionally, using specific task runners like
ConcurrentTaskRunner
,
DaskTaskRunner
, or
RayTaskRunner
can help in achieving parallel execution of tasks. Here's an example using `task.map`:
Copy code
@flow
def my_flow():
    task_a.map([1, 2, 3])
For more information, you can refer to the Prefect Task Runners documentation and the Mapping over Iterables section.
It seems you're right in your understanding. Parallelism is not automatic due to the dynamic nature of flows in Prefect. Here's a concise summary: 1. Explicit Parallelization: You need to explicitly define parallelization in your flow, for example, using
task.map
. 2. Example of
task.map
:
Copy code
@flow
   def my_flow():
       task_a.map([1, 2, 3])
3. Concurrency Limits: Concurrency can be managed using concurrency context managers if needed. 4. Documentation on Mapping: More details can be found here. 5. Concurrent Tasks Example: More advanced examples involving concurrency can be found here. For a detailed code example related to mapping tasks, see this code example.