partialsort by either alg

src/sorting.jl

@@ -899,7 +899,7 @@ function bitonic_sort!(c; by = identity, lt = isless, rev = false, dims=1)
         size(c)[dims], length(c) ÷ size(c)[dims]
     end
 
-    # compile kernels (using Int32 for indexing, if possible, yielding a 10% speedup)
+    # compile kernels (using Int32 for indexing, if possible, yielding a 70% speedup)
     I = c_len <= typemax(Int32) ? Int32 : Int
     args1 = (c, I(c_len), one(I), one(I), one(I), by, lt, Val(rev), Val(dims))
     kernel1 = @cuda launch=false comparator_small_kernel(args1...)
@@ -989,7 +989,7 @@ function Base.sort(c::AnyCuArray; kwargs...)
 end
 
 function Base.partialsort!(c::AnyCuVector, k::Union{Integer, OrdinalRange};
-                           lt=isless, by=identity, rev=false)
+                           lt=isless, by=identity, rev=false, alg::QuickSortAlg)
     # for reverse sorting, invert the less-than function
     if rev
         lt = !lt
@@ -1008,6 +1008,22 @@ function Base.partialsort!(c::AnyCuVector, k::Union{Integer, OrdinalRange};
     return out(k)
 end
 
+function Base.partialsort!(c::AnyCuVector, k::Union{Integer, OrdinalRange};
+    lt=isless, by=identity, rev=false, alg::SortingAlgorithm=BitonicSort)
+
+    function out(k :: OrdinalRange)
+        return copy(c[k])
+    end
+
+    # work around disallowed scalar index
+    function out(k :: Integer)
+        return Array(c[k:k])[1]
+    end
+
+    sort!(c, alg=alg; lt, by, rev)
+    return out(k)
+end
+
 function Base.partialsort(c::AnyCuArray, k::Union{Integer, OrdinalRange}; kwargs...)
     return partialsort!(copy(c), k; kwargs...)
 end