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[Archived] osu!mania SR calculation bugged when copy pasting the entire map

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Ryu Sei
2,897 posts
Joined October 2013
Topic Starter
Ryu Sei
Problem details:
I have two identical maps in structure (i.e same note locations, same LN locations, same LN duration), except one of them is copy-pasted and has SV gimmicks. The copied beatmap has significantly different SR than the original one.

Both maps has different notes in line order when the .osu file is opened in Notepad++ due to how osu! handles copy-paste osu!mania maps.

We can rule out the possiblity of BPM gimmicks affecting the SR since I don't use any. I only use SV gimmicks.

This also affects web-based SR calculation too.

Video or screenshot showing the problem:

In-game screenshots


Example of affected beatmap:
beatmapsets/1945296

osu! version: Stable 20230206 (latest)
Wandie
53 posts
Joined April 2021
Wandie
Strange. It happens to me too.

I tried copy and pasting your map and it yields the changed difficulty.
I copy and pasted the changed diff again and it yields to the original difficulty.
And I copy and pasted the changed changed diff, again, and it yields to the changed difficulty.
All in terms of SR.

Apparently there are 2 alternative calculations of the Star Rating of a map.

This is so weird.

Your map is the only one that is currently being heavily affected with this though, I don't have much luck finding other maps with this big of a difference except for changes like -+0.01 to -+0.08 SR.
Last edited by Wandie , edited 1 time in total.
Ryu Sei
2,897 posts
Joined October 2013
Topic Starter
Ryu Sei
Logically, if the beatmap content is the same, the SR must be the same, no matter how many times you copy and paste it. This isn't always the case for osu!mania.

The effect of this bug can be possibly exploited, from making a PP farm map due to unintended SR increase, or instead harm the mappers due to unintended SR decrease which raises the perspective of "underrated" beatmap.
Death
Technical Support Team
20,477 posts
Joined September 2013
Death
Pretty sure small discrepancies like this are known given that some of the notes appear in slightly different orders in the .osu files (even if the map itself is identical).

But may be worthwhile creating a new discussion post for this here considering the web's difficulty calculation is part of the lazer codebase. Any SR calculations taking place in stable are legacy as far as I know.
Ryu Sei
2,897 posts
Joined October 2013
Topic Starter
Ryu Sei
Discussion open: https://github.com/ppy/osu/discussions/22745
Death
Technical Support Team
20,477 posts
Joined September 2013
Death
Thanks 👍. After having thought about it a bit more, I may have been wrong about this being something that's known. I believe I was thinking about slight offset differences, not out of order objects.

Nevertheless, that repo should still be the correct place to bring this to the attention of individuals who would be able to provide the actual answer. Just wanted to clarify.
Ryu Sei
2,897 posts
Joined October 2013
Topic Starter
Ryu Sei
We can archive this thread for a while.
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