fix: Initialize model _steps and _time during __new__

[rht]

The problem is that #1942 added _steps and _time during model __init__. _steps is used in the data collector and batch_run, so that both support a scheduler-less model implementation. #1942 broke backward compatibility because it requires super().__init__() inside user's model __init__.

This is to retain backward compatibility with Mesa 2.1.x behavior where a model super().__init__() is not necessary.

[rht]

Tested manually by running https://github.com/projectmesa/mesa-examples/blob/34e92d2c29a99e950bc17f7cac860c5b13156b21/examples/bank_reserves/batch_run.py without model super().__init__().

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
Schelling	small	🔵 +0.0% [-0.4%, +0.5%]	🔵 -0.1% [-0.3%, +0.2%]
Schelling	large	🔵 +0.5% [-1.0%, +2.8%]	🔵 +4.4% [+0.4%, +9.2%]
WolfSheep	small	🔵 +1.0% [+0.6%, +1.4%]	🔵 -0.2% [-0.4%, -0.0%]
WolfSheep	large	🔵 +1.3% [+0.6%, +2.1%]	🔵 +3.8% [+1.7%, +5.8%]
BoidFlockers	small	🔵 -1.2% [-1.8%, -0.6%]	🔵 +1.3% [+0.8%, +1.9%]
BoidFlockers	large	🔵 -0.7% [-1.4%, +0.2%]	🔵 +0.8% [+0.4%, +1.3%]

[Corvince]

Good, quick fix.

[rht]

cc: @EwoutH for patch release.

[EwoutH]

Will try to do tonight, and will make screen recording so others can do it as well.

Only this PR needs to be included right?

[EwoutH]

Could someone write a 3-sentence summary with which problem this fixes for the 2.2.5 release notes?

[rht]

The problem is that #1942 added _steps and _time during model __init__. _steps is used in the data collector and batch_run, so that both support a scheduler-less model implementation. #1942 broke backward compatibility because it requires super().__init__() inside user's model __init__. This PR is to have the backward compatibility back.

[rht]

@EwoutH amended PR description. You may pick whichever version you prefer.

[rht]

@EwoutH I know about doing the cherry picking and adding a tag for a release, but I'm not sure about the auto-draft for the release note. Still pending a release checklist (which has more automation than in the past) from your end.

[EwoutH]

Checklist is here: #1917 (comment)

Could you also convert https://github.com/projectmesa/mesa/blob/main/CONTRIBUTING.rst to markdown? Then I will add the checklist to it.

Go ahead of the patch release. Make sure to cherry pick from main to 2.2.x-maintenance. If you have any questions, hit me up! (Matrix is probably the fastest)

[rht]

I looked at the checklist. Step 1 definitely can be scripted in a code as an automated check. Step 2 can be automated as well (API call with draft boolean). Step 3 can be input as a CLI flag. And so on.

[rht]

I made the script for step 1 with the help of ChatGPT:

$ python fetch_unlabeled_prs.py
PR #2039: tests: Speed up test_batch_run - Merged at: 2024-02-16T12:58:38Z
PR #2029: [pre-commit.ci] pre-commit autoupdate - Merged at: 2024-02-05T22:57:38Z

Will update once I have automated the rest.