stl algorithms for host objects

Co-authored-by: David Wendt <[email protected]>

cpp/tests/reductions/reduction_tests.cpp

@@ -33,7 +33,6 @@
 #include <cudf/types.hpp>
 #include <cudf/wrappers/timestamps.hpp>
 
-#include <thrust/copy.h>
 #include <thrust/iterator/counting_iterator.h>
 
 #include <algorithm>
@@ -775,7 +774,7 @@ double calc_var(std::vector<T> const& v, int ddof, std::vector<bool> const& mask
   auto const values = [&]() {
     if (mask.empty()) { return v; }
     std::vector<T> masked{};
-    thrust::copy_if(
+    std::copy_if(
       v.begin(), v.end(), mask.begin(), std::back_inserter(masked), [](auto m) { return m; });
     return masked;
   }();