included test and code for halton sequence, can be used in diverse ps…

…eudo-random gen

src/BlackBoxOptim.jl

@@ -93,6 +93,7 @@ export  Optimizer, AskTellOptimizer, SteppingOptimizer, PopulationOptimizer,
 module Utils
   include("utilities/latin_hypercube_sampling.jl")
   include("utilities/assign_ranks.jl")
+  include("utilities/halton_sequence.jl")
 end
 
 include("search_space.jl")

src/utilities/halton_sequence.jl

@@ -16,14 +16,14 @@ end
   Implementation is based on the psudo code in:
     http://en.wikipedia.org/wiki/Halton_sequence
 """
-function haltonnumber(base, index)
+function haltonnumber(base::Integer, index::Integer)
   res = 0
   f = 1 / base
   i = index
 
   while (i > 0)
     res += f * (i % base)
-    i = ifloor(i / base)
+    i = floor(Integer, i / base)
     f = f / base
   end
 

test/runtests.jl

@@ -6,6 +6,7 @@ import Compat.String
 my_tests = [
 
   "utilities/test_latin_hypercube_sampling.jl",
+  "utilities/test_halton_sequence.jl",
   "utilities/test_assign_ranks.jl",
 
   "test_parameters.jl",

test/utilities/test_halton_sequence.jl

@@ -0,0 +1,44 @@
+haltonnumber = BlackBoxOptim.Utils.haltonnumber
+haltonsequence = BlackBoxOptim.Utils.haltonsequence
+
+# The Halton sequence with base 2 according to http://en.wikipedia.org/wiki/Halton_sequence
+HaltonSequence2 = [
+    1/2, 1/4, 3/4, 1/8, 5/8, 3/8, 7/8, 1/16, 9/16
+]
+
+# The Halton sequence with base 2 according to http://en.wikipedia.org/wiki/Halton_sequence
+HaltonSequence3 = [
+    1/3, 2/3, 1/9, 4/9, 7/9, 2/9, 5/9, 8/9, 1/27
+]
+
+@testset "Halton numbers and sequence" begin
+
+    @testset "Halton numbers" begin
+
+        map(1:length(HaltonSequence2)) do i
+            @test isapprox(haltonnumber(2, i), HaltonSequence2[i])
+        end
+
+        map(1:length(HaltonSequence3)) do i
+            @test isapprox(haltonnumber(3, i), HaltonSequence3[i])
+        end
+
+    end
+
+    @testset "Halton sequences" begin
+
+        hseq2 = haltonsequence(2, length(HaltonSequence2))
+        @test length(hseq2) == length(HaltonSequence2)
+        map(1:length(HaltonSequence2)) do i
+            @test isapprox(hseq2[i], HaltonSequence2[i])
+        end
+
+        hseq3 = haltonsequence(3, length(HaltonSequence3))
+        @test length(hseq3) == length(HaltonSequence3)
+        map(1:length(HaltonSequence3)) do i
+            @test isapprox(hseq3[i], HaltonSequence3[i])
+        end
+
+    end
+
+end