# Several rooms, explicit shared worlds

Prerequisites: [room setup](agent-rooms.md) and a free-threaded Python runtime.
The concurrency example opens a private room for each worker and points the rooms
at one shared target world. Each room owns its workstation and memory subscriptions.

## Check results across the boundary

Generated code places its answer in `result`; the execution payload carries that
answer alongside acceptance and error information. Expert 21 starts with a single
sum, then launches four coordinated workers and checks the exact results:
`5050`, `9`, `"0-1-4-9-16"`, and `5040`.

It also checks that the workstations have distinct identities. This demonstrates
private working spaces with a shared runtime target. It is not a timing benchmark
and does not establish a universal absence of contention.

## Match coordination to the operation

Computing an answer and changing topology have different coordination needs.
Continue to the [admission and gate guide](transactions.md) for structural changes
and shutdown. Use [multiple-world targeting](agent-rooms.md) when workers should
operate on different runtime worlds rather than a shared one.


## The workflow in code

These are the core steps from the saved example. Use its complete linked script for all class definitions and setup.

```{literalinclude} ../downloads/04_expert/21_many_agents_writing_code_at_once.py
:language: python
:pyobject: main
:linenos:
```


## Runnable examples

- [Many agents writing code at once](../examples/expert/21-many-agents-writing-code-at-once.md) — Expert 21
- [One workshop many worlds](../examples/expert/13-one-workshop-many-worlds.md) — Expert 13
- [The gate that waits for readers](../examples/expert/35-the-gate-that-waits-for-readers.md) — Expert 35

[All expert examples](../examples/expert/index.md) · [Level contents](index.md) · [Full contents](../contents.md)

[Canonical page source](https://github.com/Synaptic724/melder/blob/4b364a338debcb1c010d0f6e9dcbbabb62945ba0/docs/expert/concurrency.md)