Skip to content

perf(Algebra/EuclideanDomain/Defs): prio decrease of EuclideanDomain.toCommRing #39263

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
kbuzzard wants to merge 2 commits into
base: master
Choose a base branch
from
+11 −0
Open

perf(Algebra/EuclideanDomain/Defs): prio decrease of EuclideanDomain.toCommRing #39263

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
cb31b2b
perf(Algebra/EuclideanDomain/Defs): prio decrease of EuclideanDomain.…
kbuzzard May 12, 2026
84f381f
add comment explaining why instance prio is being lowered
kbuzzard May 12, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
11 changes: 11 additions & 0 deletions Mathlib/Algebra/EuclideanDomain/Defs.lean
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,17 @@ class EuclideanDomain (R : Type u) extends CommRing R, Nontrivial R where
/-- An additional constraint on `r`. -/
mul_left_not_lt : ∀ (a) {b}, b ≠ 0 → ¬r (a * b) a

/-
Lean has far more theorems about fields than about Euclidean domains. We thus
lower the priority of `Euclideandomain.toCommRing`, encouraging typeclass inference
to try `Field.toCommRing` first. Without this priority-lowering, typeclass inference
finds the more inefficient path `Field.toEuclideanDomain.toCommRing` by default. This
priority change saves over 500G instructions across mathlib. See
https://leanprover.zulipchat.com/#narrow/channel/287929-mathlib4/topic/We.20need.20to.20talk.20about.20Euclidean.20Domains/near/594655420
-/
-- see Note [lower instance priority]
attribute [instance 100] EuclideanDomain.toCommRing

namespace EuclideanDomain

variable {R : Type u} [EuclideanDomain R]
Expand Down
Loading