Unresolved Thread Pool Configuration in Ren'Py’s renpy.fetch

Answer: The unresolved design decision

The Ren'Py team has not yet decided whether to expose a dynamic, demand‑driven thread pool for renpy.fetch or to keep the pool size fixed and only configurable at start‑up via config.fetch_thread_count. This leaves the trade‑off between a predictable, static pool and a flexible, auto‑scaling pool as an open question.

Likely explanation vs. confirmed facts

• Likely explanation: The internal thread pool size is governed by the Ren'Py configuration variable config.fetch_thread_count, which determines how many worker threads are available for background asset downloads.
• Confirmed fact (Ren'Py 7.x‑8.x docs): config.fetch_thread_count defaults to 4 and can be set in options.rpy or at runtime with python: config.fetch_thread_count = N before any fetch calls are made.

Steps to adjust the pool size for your game

1. Open (or create) options.rpy in your project.
2. Add or modify the line:

   # Set the number of concurrent fetch threads (default 4)
   config.fetch_thread_count = 8   # example value

3. Save the file and restart the game; the new value takes effect for all subsequent renpy.fetch calls.
4. To verify the current setting at runtime, insert a Python block early in your script:

   python:
       print('fetch thread count:', config.fetch_thread_count)

5. Observe loading behavior by timing a batch of renpy.fetch calls (e.g., loading several images) and comparing elapsed time before and after changing the count.

Missing diagnostic detail that could change the recommendation

To choose an optimal fetch_thread_count you need to know the number of usable CPU cores on the target platform. If you can provide that detail, the recommendation can be refined (e.g., set the count to ≤ core count to avoid excessive contention).