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Mathematically impossible most common BPM? [confirmed] [resolved]

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Total Posts
12
Nebilim
12 posts
Joined October 2009
Topic Starter
Nebilim
Explain the issue you are having:
On this map, osu reports a BPM range of 150-200 and an average BPM of 143 on the beatmap selection screen, which is not possible.


Is it reproducible? If so, explain the steps to do so:

1. Download the above map
2. Click on it in the beatmap selection screen
3. The information in the upper left shows an incorrect average BPM.



Include any relevant video or screenshots, and hardware information for hard crashes or lag issues:
MMzz
Elite Mapper
3,979 posts
Joined June 2009
MMzz
Might be because your BPMs are weird. >150.001 >199.995. It could be messing up the maths.

(BTW THIS HAS NOTHING TO DO WITH THIS PROBLEM BUT: You only need 1 timing section, use green lines for speedups. The BPM does not actually change to 200bpm)
Mismagius
9,237 posts
Joined July 2008
Mismagius
this kinda should be fixed (warning: lots of pics)










no, none of these maps have broken timing or anything. they are perfectly normal multiBPM songs.
Last edited by Mismagius , edited 9 times in total.
[Luanny]
8,248 posts
Joined April 2011
[Luanny]
you broke math, m8
ZeroEightOne
240 posts
Joined August 2011
ZeroEightOne
Some maps have the correct AVG BPM, example :-
http://osu.ppy.sh/b/41865

BPMs are : 140 , 145 , 145.3 , 125 , 134 , 144
AVG = 138.8833333333333333333......
In game = 139

But some of maps have the negative average BPM.

And Finally :-
Go home Math
You are drunk.
TheVileOne
osu! Alumni
8,431 posts
Joined March 2010
TheVileOne
I'm not sure I should be confirming a Testbuild issue, but peppy can unconfirm it if it's not supposed to be confirmed.
Mismagius
9,237 posts
Joined July 2008
Mismagius
This is a public build issue, not test.
peppy
19,301 posts
Here since the beginning
peppy
This should be fixed in the next public release.
statementreply
Pro Tester
307 posts
Joined June 2009
statementreply
Average BPM is still not correctly calculated on latest test build (2012-12-28T09:27:48Z).
SPOILER
[20:22:05] <@peppy> then report it
[20:22:07] <@peppy> in that thread

http://osu.ppy.sh/b/85520
In game: 152-192 (~140)
SPOILER
Correct: 192

The following maps' average BPM in game lies within its BPM range, but it's widely inaccurate.

http://osu.ppy.sh/b/85355
In game: 152-192 (~169)
Correct: 188.062 (geometric mean, may be slightly different depending on how it is actually calculated)

http://osu.ppy.sh/b/170608
In game: 81-96 (~92)
Correct: 95.937

http://osu.ppy.sh/b/61124
In game: 75-168 (~105)
Correct: 164.907

http://osu.ppy.sh/b/188562
In game: 75-174 (~147)
Correct: 167.769

EDIT: Fixed explanation
peppy
19,301 posts
Here since the beginning
peppy
Do the above cases still incur any error with the new display?
statementreply
Pro Tester
307 posts
Joined June 2009
statementreply

statementreply wrote:

peppy wrote:

I've changed this, since I too do not agree with the current implementation. Is up on test build if you would like to test it out.
Would median or 75th percentile (or some other percentile) make more sense? (eg. on maps like ΔMAX)

Anyway it's broken on 2012-12-28T16:19:30Z test build
SPOILER

Edit: x% percentile := y bpm so that ≤x% of draining time is in <y bpm sections and ≤(100-x)% of draining time is in >y bpm sections
bwross
265 posts
Joined December 2009
bwross
I haven't seen anything mathematically impossible yet in the new version (although I've only done a bit of looking), but there are still some very questionable results, like Flutter Girl ("75-168 (75)"... 75 BPM is easily the least representative BPM in the song, it's used for 2 very short transitional retards between the 166 Waltz/168 Common sections).

As for using median/percentile, I don't think it really makes much difference except in weird exceptional cases like medleys and deltaMax, so it's acceptable if things don't work too well for them (range is probably good enough for them). For most maps, the mode and the median are going to be the same because one BPM will dominate almost all of the song. Median is just a bit more prone to catching a value that represents very little of the map (although it requires some coincidences to happen), whereas mode guarantees that you represent as much of the map as possible with a single value.
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