From 3d946ecb711cea4012f8af1ad2ed8e72065445b1 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Mon, 25 Feb 2019 18:59:49 +0200
Subject: [PATCH] Add benchmark2.cpp

---
 benchmark/benchmark1.cpp |   7 ++
 benchmark/benchmark2.cpp | 149 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 156 insertions(+)
 create mode 100644 benchmark/benchmark2.cpp

diff --git a/benchmark/benchmark1.cpp b/benchmark/benchmark1.cpp
index 07cd5d0..703f891 100644
--- a/benchmark/benchmark1.cpp
+++ b/benchmark/benchmark1.cpp
@@ -1,3 +1,10 @@
+// Copyright 2019 Peter Dimov
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
 #if defined(ONLY_V2)
 # define NO_BV
 # define NO_SV
diff --git a/benchmark/benchmark2.cpp b/benchmark/benchmark2.cpp
new file mode 100644
index 0000000..bea5f3a
--- /dev/null
+++ b/benchmark/benchmark2.cpp
@@ -0,0 +1,149 @@
+// Copyright 2019 Peter Dimov
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+#if defined(ONLY_V2)
+# define NO_BV
+# define NO_SV
+#endif
+
+#if defined(ONLY_BV)
+# define NO_V2
+# define NO_SV
+#endif
+
+#if defined(ONLY_SV)
+# define NO_V2
+# define NO_BV
+#endif
+
+#if !defined(NO_V2)
+#include <boost/variant2/variant.hpp>
+#endif
+
+#if !defined(NO_BV)
+#include <boost/variant.hpp>
+#endif
+
+#if !defined(NO_SV)
+#include <variant>
+#endif
+
+#include <type_traits>
+#include <chrono>
+#include <iostream>
+#include <iomanip>
+#include <vector>
+
+struct prefix
+{
+    int v_;
+};
+
+struct X1: prefix {};
+struct X2: prefix {};
+struct X3: prefix {};
+struct X4: prefix {};
+struct X5: prefix {};
+struct X6: prefix {};
+struct X7: prefix {};
+struct X8: prefix {};
+struct X9: prefix {};
+struct X10: prefix {};
+struct X11: prefix {};
+struct X12: prefix {};
+
+inline int get_value( prefix const& v )
+{
+    return v.v_;
+}
+
+#if !defined(NO_V2)
+
+template<class... T> int get_value( boost::variant2::variant<T...> const& v )
+{
+    return visit( []( prefix const& x ) { return x.v_; }, v );
+}
+
+#endif
+
+#if !defined(NO_BV)
+
+template<class... T> int get_value( boost::variant<T...> const& v )
+{
+    return boost::apply_visitor( []( prefix const& x ) { return x.v_; }, v );
+}
+
+#endif
+
+#if !defined(NO_SV)
+
+template<class... T> int get_value( std::variant<T...> const& v )
+{
+    return visit( []( prefix const& x ) { return x.v_; }, v );
+}
+
+#endif
+
+template<class V> void test_( int N )
+{
+    std::vector<V> w;
+    // lack of reserve is deliberate
+
+    auto tp1 = std::chrono::high_resolution_clock::now();
+
+    for( int i = 0; i < N / 12; ++i )
+    {
+        w.push_back( X1{ i } );
+        w.push_back( X2{ i } );
+        w.push_back( X3{ i } );
+        w.push_back( X4{ i } );
+        w.push_back( X5{ i } );
+        w.push_back( X6{ i } );
+        w.push_back( X7{ i } );
+        w.push_back( X8{ i } );
+        w.push_back( X9{ i } );
+        w.push_back( X10{ i } );
+        w.push_back( X11{ i } );
+        w.push_back( X12{ i } );
+    }
+
+    unsigned long long s = 0;
+
+    for( std::size_t i = 0, n = w.size(); i < n; ++i )
+    {
+        s = s + get_value( w[ i ] );
+    }
+
+    auto tp2 = std::chrono::high_resolution_clock::now();
+
+    std::cout << std::setw( 6 ) << std::chrono::duration_cast<std::chrono::milliseconds>( tp2 - tp1 ).count() << " ms; S=" << s << "\n";
+}
+
+template<class... T> void test( int N )
+{
+    std::cout << "N=" << N << ":\n";
+
+    std::cout << "        prefix: "; test_<prefix>( N );
+#if !defined(NO_V2)
+    std::cout << "      variant2: "; test_<boost::variant2::variant<T...>>( N );
+#endif
+#if !defined(NO_BV)
+    std::cout << "boost::variant: "; test_<boost::variant<T...>>( N );
+#endif
+#if !defined(NO_SV)
+    std::cout << "  std::variant: "; test_<std::variant<T...>>( N );
+#endif
+
+    std::cout << '\n';
+}
+
+int main()
+{
+    int const N = 100'000'000;
+
+    test<X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12>( N );
+}