Optimize clamp

src/FixedPointNumbers.jl

@@ -4,7 +4,7 @@ import Base: ==, <, <=, -, +, *, /, ~, isapprox,
              convert, promote_rule, show, bitstring, abs, decompose,
              isnan, isinf, isfinite, isinteger,
              zero, oneunit, one, typemin, typemax, floatmin, floatmax, eps, reinterpret,
-             big, rationalize, float, trunc, round, floor, ceil, bswap,
+             big, rationalize, float, trunc, round, floor, ceil, bswap, clamp,
              div, fld, rem, mod, mod1, fld1, min, max, minmax,
              rand, length
 
@@ -183,6 +183,12 @@ bitstring(x::FixedPoint) = bitstring(x.i)
 
 bswap(x::X) where {X <: FixedPoint} = sizeof(X) == 1 ? x : X(bswap(x.i), 0)
 
+# At least on Julia v1.5.0 or earlier, the following specialization helps the
+# SIMD vectorization. (cf. PR #194)
+clamp(x::X, lo::X, hi::X) where {X <: FixedPoint} = X(clamp(x.i, lo.i, hi.i), 0)
+
+clamp(x, ::Type{X}) where {X <: FixedPoint} = clamp(x, typemin(X), typemax(X)) % X
+
 for f in (:zero, :oneunit, :one, :eps, :rawone, :rawtype, :floattype)
     @eval begin
         $f(x::FixedPoint) = $f(typeof(x))

test/fixed.jl

@@ -406,6 +406,19 @@ end
     @test bswap(Q0f15(0.5)) === reinterpret(Q0f15, signed(0x0040))
 end
 
+@testset "clamp" begin
+    @test clamp(0.5Q0f7, -0.8Q0f7,  0.8Q0f7) === 0.5Q0f7
+    @test clamp(0.5Q0f7, 0.75Q0f7,  0.8Q0f7) === 0.75Q0f7
+    @test clamp(0.5Q0f7, -0.8Q0f7, 0.25Q0f7) === 0.25Q0f7
+    @test clamp(0.5,      -0.8Q0f7,  0.8Q0f7) === 0.5
+    @test clamp(0.5f0,    0.75Q0f7,  0.8Q0f7) === 0.75f0
+    @test clamp(0.5Q0f15, -0.8Q0f7, 0.25Q0f7) === 0.25Q0f15
+    @test clamp(0.5Q0f7, -Inf, Inf) === 0.5
+    @test clamp(0.5,     Q0f7) === 0.5Q0f7
+    @test clamp(-1.5f0,  Q0f7) === -1.0Q0f7
+    @test clamp(1.5Q1f6, Q0f7) === 0.992Q0f7
+end
+
 @testset "Promotion within Fixed" begin
     @test @inferred(promote(Q0f7(0.25), Q0f7(0.75))) ===
         (Q0f7(0.25), Q0f7(0.75))

test/normed.jl

@@ -338,6 +338,19 @@ end
     @test minmax(N0f8(0.8), N0f8(0.2)) === (N0f8(0.2), N0f8(0.8))
 end
 
+@testset "clamp" begin
+    @test clamp(0.5N0f8, 0.2N0f8, 0.8N0f8) === 0.5N0f8
+    @test clamp(0.5N0f8, 0.6N0f8, 0.8N0f8) === 0.6N0f8
+    @test clamp(0.5N0f8, 0.2N0f8, 0.4N0f8) === 0.4N0f8
+    @test clamp(0.5,      0.2N0f8, 0.8N0f8) === 0.5
+    @test clamp(0.5f0,    0.6N0f8, 0.8N0f8) === 0.6f0
+    @test clamp(0.5N0f16, 0.2N0f8, 0.4N0f8) === 0.4N0f16
+    @test clamp(0.6N0f8, -Inf, Inf) === 0.6
+    @test clamp(0.5,     N0f8) === 0.5N0f8
+    @test clamp(-1.0f0,  N0f8) === 0.0N0f8
+    @test clamp(2.0N1f7, N0f8) === 1.0N0f8
+end
+
 @testset "unit range" begin
     @test length(N0f8(0):N0f8(1)) == 2
     @test length(N0f8(1):N0f8(0)) == 0