Divrem speedup and tests (#39045)

fixes #22219
JuliaLang · Nov 18, 2021 · 616de75 · 616de75
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diff --git a/base/div.jl b/base/div.jl
@@ -156,6 +156,8 @@ julia> divrem(7,3)
 ```
 """
 divrem(x, y) = divrem(x, y, RoundToZero)
+
+
 function divrem(a, b, r::RoundingMode)
     if r === RoundToZero
         # For compat. Remove in 2.0.
@@ -167,6 +169,25 @@ function divrem(a, b, r::RoundingMode)
         (div(a, b, r), rem(a, b, r))
     end
 end
+#avoids calling rem for Integers-Integers (all modes),
+#a-d*b not precise for Floats - AbstractFloat, AbstractIrrational. Rationals are still slower
+function divrem(a::Integer, b::Integer, r::Union{typeof(RoundUp),
+                                                typeof(RoundDown),
+                                                typeof(RoundToZero)})
+    if r === RoundToZero
+        # For compat. Remove in 2.0.
+        d = div(a, b)
+        (d, a - d*b)
+    elseif r === RoundDown
+        # For compat. Remove in 2.0.
+        d = fld(a, b)
+        (d, a - d*b)
+    elseif r === RoundUp
+        # For compat. Remove in 2.0.
+        d = div(a, b, r)
+        (d, a - d*b)
+    end
+end
 function divrem(x::Integer, y::Integer, rnd::typeof(RoundNearest))
     (q, r) = divrem(x, y)
     if x >= 0

diff --git a/test/numbers.jl b/test/numbers.jl
@@ -2549,6 +2549,41 @@ end
     end
 end
 
+@testset "divrem rounded" begin
+    #rounded Floats
+    for T in (Float16, Float32, Float64, BigFloat)
+        @test divrem(T(1.5), T(2), RoundToZero)[2]  == 1.5
+        @test divrem(T(1.5), T(2), RoundNearest)[2] == -0.5
+        @test divrem(T(1.5), T(2), RoundDown)[2]    == 1.5
+        @test divrem(T(1.5), T(2), RoundUp)[2]      == -0.5
+        @test divrem(T(-1.5), T(2), RoundToZero)[2]  == -1.5
+        @test divrem(T(-1.5), T(2), RoundNearest)[2] == 0.5
+        @test divrem(T(-1.5), T(2), RoundDown)[2]    == 0.5
+        @test divrem(T(-1.5), T(2), RoundUp)[2]      == -1.5
+    end
+    #rounded Integers
+    for (a, b) in (
+            (3, 2),
+            (5, 3),
+            (-3, 2),
+            (5, 2),
+            (-5, 2),
+            (-5, 3),
+            (5, -3))
+        for sign in (+1, -1)
+            (a, b) = (a*sign, b*sign)
+            @test divrem(a, b, RoundNearest) == (div(a, b, RoundNearest),rem(a, b, RoundNearest))
+        end
+    end
+
+    a = 122322388883338838388383888823233122323
+    b = 343443
+    c = 122322388883338838388383888823233122333
+    @test divrem(a, b) == (div(a,b), rem(a,b))
+    @test divrem(a, c) == (div(a,c), rem(a,c))
+    @test divrem(a,-(a-20), RoundDown) == (div(a,-(a-20), RoundDown), rem(a,-(a-20), RoundDown))
+end
+
 @testset "rem2pi $T" for T in (Float16, Float32, Float64, BigFloat)
     @test rem2pi(T(1), RoundToZero)  == 1
     @test rem2pi(T(1), RoundNearest) == 1