perf: improves the performance of the `Repr (Equiv.Perm α)` instance

[Komyyy]

---

[jcommelin]

!bench

[leanprover-bot]

Here are the benchmark results for commit ad895f31658261254c22f03502b7c96917c2eb93. There were no significant changes against commit d4e8dd237c13d49d33bd63c45199b142b7d5f82b.

[Komyyy]

@eric-wieser #13214

[github-actions[bot]]

PR summary 880283a729

Import changes for modified files

Dependency changes

File	Base Count	Head Count	Change
Mathlib.GroupTheory.Perm.Cycle.Basic	903	902	-1 (-0.11%)

Import changes for all files

Files

Import difference

9 files Mathlib.Algebra.Order.Chebyshev Mathlib.Combinatorics.Additive.Corner.Roth Mathlib.Combinatorics.SimpleGraph.Regularity.Bound Mathlib.Combinatorics.SimpleGraph.Regularity.Chunk Mathlib.Combinatorics.SimpleGraph.Regularity.Increment Mathlib.Combinatorics.SimpleGraph.Regularity.Lemma Mathlib.Combinatorics.SimpleGraph.Triangle.Removal Mathlib.GroupTheory.Perm.Closure Mathlib.GroupTheory.Perm.Cycle.Basic

-1

---

Declarations diff

+ instDecidableRelSameCycle - instance (f : Perm α) [DecidableRel (SameCycle f⁻¹)] : - instance [Fintype α] [DecidableEq α] (f : Perm α) : DecidableRel (SameCycle f) := fun x y =>

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

---

No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[grunweg]

@Komyyy Coming here for PR triage: thanks for your PR. It currently has a merge conflict, which means it won't show up in the review queue (and is less likely to be noticed). Can you merge the master branch, please?

[Komyyy]

@grunweg Sorry for the lack of updates due to mental problems over the past 5 months.

[Komyyy]

@YaelDillies #20519

[mathlib4-dependent-issues-bot]

This PR/issue depends on:

• ~~leanprover-community/mathlib4#20538~~ By Dependent Issues (🤖). Happy coding!

[YaelDillies]

Can you merge master to reduce the diff?

[Komyyy]

@YaelDillies Merged.

[github-actions[bot]]

🚀 Pull request has been placed on the maintainer queue by YaelDillies.

[jcommelin]

Thanks :tada:

bors merge

[mathlib-bors[bot]]

Pull request successfully merged into master.

Build succeeded:

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