From 370d4524abf8ca6078f2ac7db4c84992c851308f Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Mon, 5 May 2025 14:40:20 +0200
Subject: [PATCH 1/2] perf: optimize `permutations` (`increment!` loop)

- The construct previously used in the `for` loop is inefficient.
- The loop can exit early as soon as `state[i] <= max` is satisfied.
- All array indexing can be marked `@inbounds`.
---
 src/permutations.jl | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/permutations.jl b/src/permutations.jl
index b6ef788..c1532ca 100644
--- a/src/permutations.jl
+++ b/src/permutations.jl
@@ -28,12 +28,14 @@ function has_repeats(state::Vector{Int})
 end
 
 function increment!(state::Vector{Int}, min::Int, max::Int)
-    state[end] += 1
-    for i in reverse(eachindex(state))[firstindex(state):end-1]
-        if state[i] > max
-            state[i] = min
-            state[i-1] += 1
-        end
+    # All array indexing can be marked inbounds because of the type restriction in the signature.
+    # If the type restriction is ever loosened, please check safety of the `@inbounds`.
+    @inbounds state[end] += 1
+    i = lastindex(state)
+    @inbounds while i > firstindex(state) && state[i] > max
+        state[i] = min
+        state[i-1] += 1
+        i -= 1
     end
 end
 

From 19b6040e14971a092a1a5b8154b39cd7e2b6969f Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Mon, 5 May 2025 16:25:39 +0200
Subject: [PATCH 2/2] style: trailing white spaces

---
 src/permutations.jl  | 6 +++---
 test/permutations.jl | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/permutations.jl b/src/permutations.jl
index c1532ca..482333c 100644
--- a/src/permutations.jl
+++ b/src/permutations.jl
@@ -16,7 +16,7 @@ end
 
 function has_repeats(state::Vector{Int})
     # This can be safely marked inbounds because of the type restriction in the signature.
-    # If the type restriction is ever loosened, please check safety of the `@inbounds`
+    # If the type restriction is ever loosened, please check safety of the `@inbounds`.
     @inbounds for outer in eachindex(state)
         for inner in (outer+1):lastindex(state)
             if state[outer] == state[inner]
@@ -98,7 +98,7 @@ permutations(a) = permutations(a, length(a))
     permutations(a, t)
 
 Generate all size `t` permutations of an indexable object `a`.
-Only works for `a` with defined length. 
+Only works for `a` with defined length.
 If `(t <= 0) || (t > length(a))`, then returns an empty vector of eltype of `a`
 
 # Examples
@@ -124,7 +124,7 @@ julia> [ (len, collect(permutations(1:3, len))) for len in -1:4 ]
 """
 function permutations(a, t::Integer)
     if t == 0
-        # Correct behavior for a permutation of length 0 is a vector containing a single empty vector 
+        # Correct behavior for a permutation of length 0 is a vector containing a single empty vector
         return [Vector{eltype(a)}()]
     elseif t == 1
         # Easy case, just return each element in its own vector
diff --git a/test/permutations.jl b/test/permutations.jl
index ae18b48..162cff7 100644
--- a/test/permutations.jl
+++ b/test/permutations.jl
@@ -30,7 +30,7 @@ end
     @test collect(permutations([], -1)) == Any[]
     @test collect(permutations([], 0)) == [Any[]]
     @test collect(permutations([], 1)) == Any[]
-    
+
     @testset "permutation lengths" begin
         expected_lengths = [1, 5, 20, 60, 120, 120]
         ks = 0:5