Use mixxx::Bpm for some Beats functions #4044

Holzhaus · 2021-07-01T20:53:53Z

Follow up to #4043. This uses the proper mixxx::Bpm type in some method signatures related to beats. I didn't change all methods to keep the diff reasonably small.

Be-ing · 2021-07-01T21:58:38Z

Converted to draft until #4043 is merged.

Holzhaus · 2021-07-02T16:57:46Z

This is ready now.

Swiftb0y

In the future, we might also want to consider making (some parts of) the Bpm class constexpr.

src/analyzer/plugins/analyzersoundtouchbeats.cpp

src/library/dlgtrackinfo.cpp

src/test/beatgridtest.cpp

src/analyzer/plugins/analyzerplugin.h

Holzhaus · 2021-07-03T12:11:21Z

I added some simple tests for the class that we can extend later. A later PR improves the Bpm class further, so I'd rather improve the class there unless you consider it a merge blocker.

src/test/bpmtest.cpp

uklotzde · 2021-07-03T13:53:15Z

src/test/bpmtest.cpp

+    EXPECT_EQ(mixxx::Bpm(120), mixxx::Bpm(240) / 2);
+
+    EXPECT_EQ(mixxx::Bpm(), mixxx::Bpm(mixxx::Bpm::kValueUndefined));
+    EXPECT_EQ(mixxx::Bpm(), mixxx::Bpm(0.0));


This last test is confusing. We could test that mixxx::Bpm::kValueUndefined equals 0.0 but that doesn't really make any sense to me. Otherwise we would need to test the value of each and every constant.

The point is that all invalid values should be equal to another. But it was actually not working, fixed that.

uklotzde · 2021-07-03T21:00:17Z

src/track/bpm.h

+    return bpm1.getValue() >= bpm2.getValue();
+}
+
+inline bool operator==(Bpm bpm1, Bpm bpm2) {


I didn't notice this very special equality comparison! We should add a comment that all invalid values are considered equal.

We also should test the comparison of invalid and valid values.

I will. But do you agree with this comparison? I think it makes sense to consider all invalid values equal.

I'm not saying we should imitate this...

❯ node Welcome to Node.js v14.17.0. Type ".help" for more information. > NaN === NaN false >

https://www.destroyallsoftware.com/talks/wat

This is actually the IEEE-754 standard. It's the same in C++. !(x == x) is a way to implement isNaN.

It could be surprising as the other comparison operators like <= behave differently! Do we really need it? Otherwise I would suggest to avoid these tweaks.

@uklotzde test added.

It could be surprising as the other comparison operators like <= behave differently! Do we really need it? Otherwise I would suggest to avoid these tweaks.

I don't know. My rationale was that someValue == Bpm() is true if someValue is some invalid value.

Btw, I actually have a WIP PR that takes care of that and raises a debug assertion every time you try to do a calculation or comparison with an invalid value: 2217470#diff-6ee8fe6454f9e7e8637c1ba82b07d85ae618df4fbb651d66f8e5fff4b06f51e5

It could be surprising as the other comparison operators like <= behave differently! Do we really need it? Otherwise I would suggest to avoid these tweaks.

I don't know. My rationale was that someValue == Bpm() is true if someValue is some invalid value.

I actually have a WIP PR that takes care of that and raises a debug assertion every time you try to do a calculation or comparison with an invalid value: 2217470#diff-6ee8fe6454f9e7e8637c1ba82b07d85ae618df4fbb651d66f8e5fff4b06f51e5

But I don't want to add all of that here. I can also revert these "all invalid values are equal" changes if you prefer.

uklotzde · 2021-07-05T07:42:00Z

src/track/bpm.h

+    return (!bpm1.hasValue() && !bpm2.hasValue()) || bpm1.getValue() <= bpm2.getValue();
+}
+
+inline bool operator>(Bpm bpm1, Bpm bpm2) {


The definitions of the comparison operators are inconsistent, i.e. the result of lhs < rhs should equal !(lhs >= rhs).

In which cases does it not?

Note that the < operator uses getValue() which throws a debug assert if at least one of the values is invalid.

50 < 100 = true
100 < 50 = false
100 < 100 = false
100 < invalid = debug assert
invalid < 100 = debug assert
invalid < invalid = debug assert

50 >= 100 = false
100 >= 100 = true
100 >= 100 = true
100 >= invalid = debug assert
invalid >= 100 = debug assert
invalid >= invalid = true (because they are equal)

Independent of debug assertions these operators must be interchangeable. Everything else is unexpected.

The condition < must result in the same behavior as not >= because as a developer I expect that I could use either of them depending on which is more suitable for structuring the code.

If I see an expression like if (!(a >= b)) I will refactor it to if (a < b).

getValue() always returns 0.0 if the value is invalid, so it should still work fine:

50 < 100 = true
100 < 50 = false
100 < 100 = false
100 < invalid = false + debug assert
invalid < 100 = true + debug assert
invalid < invalid = false debug assert

50 >= 100 = false
100 >= 100 = true
100 >= 100 = true
100 >= invalid = true + debug assert
invalid >= 100 = false + debug assert
invalid >= invalid = true

Usually you only implement < and then the remaining operators in terms of this to prevent inconsistencies.

uklotzde · 2021-07-05T20:27:43Z

src/track/bpm.h

+    return bpm1.getValue() > bpm2.getValue();
+}
+
+inline bool operator>=(Bpm bpm1, Bpm bpm2) {


Both > and >= should delegate to < and <= with the arguments switched.

good point.

uklotzde · 2021-07-05T22:54:08Z

Please fix the code style issues, then we can merge.

uklotzde

Thank you! I guess the extra rounds during the review were worth the efforts ;) LGTM

Holzhaus added the code quality label Jul 1, 2021

github-actions bot added build library labels Jul 1, 2021

Be-ing marked this pull request as draft July 1, 2021 21:58

Holzhaus mentioned this pull request Jul 1, 2021

Use mixxx::Bpm for some Beats functions Pt. 2 #4045

Merged

Holzhaus force-pushed the bpm branch from 77d726b to 2121b78 Compare July 2, 2021 13:32

Holzhaus added 2 commits July 2, 2021 18:51

Bpm: Add more operator overrides

db34509

Beats: Add mixxx::Bpm in BeatUtils and BeatGrid/BeatMap classes

96e0d64

Holzhaus force-pushed the bpm branch from 2121b78 to 96e0d64 Compare July 2, 2021 16:54

Holzhaus marked this pull request as ready for review July 2, 2021 16:54

Swiftb0y reviewed Jul 2, 2021

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uklotzde reviewed Jul 3, 2021

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Bpm: Fix comparison of invalid values

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Holzhaus force-pushed the bpm branch from 5798363 to a0cd94f Compare July 3, 2021 20:32

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Holzhaus force-pushed the bpm branch from a0cd94f to f8ca914 Compare July 3, 2021 22:12

test: Add some simple tests for Bpm class

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Holzhaus force-pushed the bpm branch from f8ca914 to db51b83 Compare July 3, 2021 22:28

Bpm: Improve and test comparison operators

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Holzhaus requested a review from uklotzde July 3, 2021 23:02

Holzhaus added 4 commits July 5, 2021 01:40

Bpm: Only access value if it's actually valid

a423ff5

Bpm: Also check for invalid values

65e04b5

Bpm: Ensure that bpm value is valid before doing any calculations

bc0d16d

Bpm: Add proper debug output

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Holzhaus force-pushed the bpm branch from 85a5b64 to 4dff17c Compare July 4, 2021 23:43

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Bpm: Simplify </<=/>/>= operator implementations

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Holzhaus force-pushed the bpm branch from 1880daa to 717c1fa Compare July 6, 2021 08:50

Holzhaus requested a review from uklotzde July 6, 2021 08:50

uklotzde approved these changes Jul 6, 2021

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uklotzde merged commit d4a6b2e into mixxxdj:main Jul 6, 2021

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Use mixxx::Bpm for some Beats functions #4044

Use mixxx::Bpm for some Beats functions #4044

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Use mixxx::Bpm for some Beats functions #4044

Use mixxx::Bpm for some Beats functions #4044

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