Add bench_partition_by.jl

benchmark/bench_partition_by.jl

@@ -0,0 +1,49 @@
+using Statistics
+using BenchmarkTools
+using Transducers
+
+function manual_partition_by(xs)
+    acc = zero(eltype(xs))
+    buffer = similar(xs, 0)
+    pval = xs[1] > 0
+    push!(buffer, xs[1])
+    for x in @view xs[2:end]
+        val = x > 0
+        if val == pval
+            push!(buffer, x)
+        else
+            if mean(abs, buffer) < 1.0
+                acc += prod(buffer)
+            end
+            empty!(buffer)
+            push!(buffer, x)
+            pval = val
+        end
+    end
+    if mean(abs, buffer) < 1.0
+        acc += prod(buffer)
+    end
+    return acc
+end
+
+let suite = BenchmarkGroup()
+
+    xf = PartitionBy(x -> x > 0) |>
+        Filter(xs -> mean(abs, xs) < 1.0) |>
+        Map(prod)
+
+    n = 10^5
+
+    let xs = randn(100)
+        @assert manual_partition_by(xs) == transduce(xf, +, 0.0, xs)
+    end
+
+    suite["xf"] = @benchmarkable(
+        transduce($xf, +, 0.0, xs),
+        setup=(xs = randn($n)))
+    suite["man"] = @benchmarkable(
+        manual_partition_by(xs),
+        setup=(xs = randn($n)))
+
+    suite
+end

benchmark/benchmarks.jl

@@ -2,3 +2,4 @@ using BenchmarkTools
 SUITE = BenchmarkGroup()
 SUITE["filter_map_reduce"] = include("bench_filter_map_reduce.jl")
 SUITE["filter_map_map!"] = include("bench_filter_map_map!.jl")
+SUITE["partition_by"] = include("bench_partition_by.jl")

src/library.jl

@@ -242,7 +242,7 @@ function next(rf::R_{PartitionBy}, result, input)
             push!(iinput, input)
         else
             iresult = next(rf.inner, iresult, iinput)
-            iinput = InType(rf)[]
+            empty!(iinput)
             isreduced(iresult) || push!(iinput, input)
         end
         return (iinput, val), iresult

test/test_library.jl

@@ -9,7 +9,7 @@ end
 
 @testset "PartitionBy" begin
     # https://clojuredocs.org/clojure.core/partition-by#example-542692c7c026201cdc3269da
-    xf = PartitionBy(isequal(3))
+    xf = PartitionBy(isequal(3)) |> Map(copy)
     @test collect(xf, 1:5) == [[1, 2], [3], [4, 5]]
 end