Merge pull request #37 from milankl/mk/keepbitsmax

No rounding for max keepbits

Project.toml

@@ -1,7 +1,7 @@
 name = "BitInformation"
 uuid = "de688a37-743e-4ac2-a6f0-bd62414d1aa7"
 authors = ["Milan <milankloewer@gmx.de> and contributors"]
-version = "0.5.0"
+version = "0.5.1"
 
 [deps]
 Distributions = "31c24e10-a181-5473-b8eb-7969acd0382f"

src/round_nearest.jl

@@ -1,8 +1,12 @@
 """Shift integer to push the mantissa in the right position. Used to determine
 round up or down in the tie case. `keepbits` is the number of mantissa bits to
-be kept (i.e. not zero-ed) after rounding."""
+be kept (i.e. not zero-ed) after rounding. Special case: shift is -1 for
+keepbits == significand_bits(T) to avoid a round away from 0 where no rounding
+should be applied."""
 function get_shift(::Type{T},keepbits::Integer) where {T<:Base.IEEEFloat}
-    return Base.significand_bits(T) - keepbits
+    shift = Base.significand_bits(T) - keepbits     # normal case
+    shift -= keepbits == Base.significand_bits(T)   # to avoid round away from 0
+    return shift
 end
 
 """Returns for a Float-type `T` and `keepbits`, the number of mantissa bits to be

test/round_nearest.jl

@@ -55,7 +55,7 @@ end
 
 @testset "No rounding for keepbits=10,23,52" begin
     for (T,k) in zip([Float16,Float32,Float64],
-                        [11,24,53])
+                        [10,23,52])
         A = rand(T,200,300)
         Ar = round(A,k)
         @test A == Ar