Merge pull request #50 from milankl/mk/decompose

Base.decompose(::BFloat16)

src/bfloat16.jl

@@ -78,6 +78,17 @@ end
 Base.exponent(x::BFloat16) =
     ((reinterpret(Unsigned, x) & Base.exponent_mask(BFloat16)) >> 7) - Base.exponent_bias(BFloat16)
 
+function Base.decompose(x::BFloat16)::NTuple{3,Int}
+    isnan(x) && return 0, 0, 0
+    isinf(x) && return ifelse(x < 0, -1, 1), 0, 0
+    n = reinterpret(UInt16, x)
+    s = (n & 0x007f) % Int16
+    e = ((n & 0x7f80) >> 7) % Int
+    s |= Int16(e != 0) << 7
+    d = ifelse(signbit(x), -1, 1)
+    s, e - 134 + (e == 0), d
+end
+
 function Base.frexp(x::BFloat16)
    xp = exponent(x) + 1
    fr = significand(x) * BFloat16(0.5)

test/runtests.jl

@@ -140,6 +140,15 @@ end
   @test isnan(prevfloat(BFloat16s.NaNB16))
 end
 
+@testset "Decompose BFloat16" begin
+  for x in randn(100)
+    bf16 = BFloat16(x)
+    s,e,d = Base.decompose(bf16)
+    @test BFloat16(s*2.0^e/d) == bf16
+  end
+end
+
+
 @testset "Next/prevfloat(x,::Integer)" begin
 
   x = one(BFloat16)
@@ -159,6 +168,5 @@ end
   @test nextfloat(-floatmin(BFloat16),2^8) > 0
 end
 
-
 include("structure.jl")
 include("mathfuncs.jl")