Using Base.Sort.InitialOptimizations (#70)

* Use initial optimizations but don't apply initial optimizations to radix sort twice

* Better comment on a test

Author: LilithHafner

src/SortingAlgorithms.jl

@@ -16,8 +16,13 @@ struct TimSortAlg   <: Algorithm end
 struct RadixSortAlg <: Algorithm end
 struct CombSortAlg  <: Algorithm end
 
-const HeapSort  = HeapSortAlg()
-const TimSort   = TimSortAlg()
+function maybe_optimize(x::Algorithm) 
+    isdefined(Base.Sort, :InitialOptimizations) ? Base.Sort.InitialOptimizations(x) : x
+end     
+const HeapSort  = maybe_optimize(HeapSortAlg())
+const TimSort   = maybe_optimize(TimSortAlg())
+# Whenever InitialOptimizations is defined, RadixSort falls 
+# back to Base.DEFAULT_STABLE which already incldues them.
 const RadixSort = RadixSortAlg()
 
 """
@@ -44,7 +49,7 @@ Characteristics:
  - Werneck, N. L., (2020). "ChipSort: a SIMD and cache-aware sorting module. JuliaCon Proceedings, 1(1), 12, https://doi.org/10.21105/jcon.00012
  - H. Inoue, T. Moriyama, H. Komatsu and T. Nakatani, "AA-Sort: A New Parallel Sorting Algorithm for Multi-Core SIMD Processors," 16th International Conference on Parallel Architecture and Compilation Techniques (PACT 2007), 2007, pp. 189-198, doi: 10.1109/PACT.2007.4336211.
 """
-const CombSort  = CombSortAlg()
+const CombSort  = maybe_optimize(CombSortAlg())
 
 
 ## Heap sort

test/runtests.jl

@@ -103,6 +103,10 @@ for n in [0:10..., 100, 101, 1000, 1001]
         # test float sorting with NaNs
         s = sort(v, alg=alg, order=ord)
         @test issorted(s, order=ord)
+        
+        # This tests that NaNs (which compare equivalent) are treated stably 
+        # even when the underlying algorithm is unstable. That it happens to
+        # pass is not a part of the public API:
         @test reinterpret(UInt64, v[map(isnan, v)]) == reinterpret(UInt64, s[map(isnan, s)])
 
         # test float permutation with NaNs