Add popcount

test/bit_popcount_test.cpp

@@ -0,0 +1,46 @@
+// Test for boost/core/bit.hpp (bit_ceil)
+//
+// Copyright 2020 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/core/bit.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/detail/splitmix64.hpp>
+#include <boost/cstdint.hpp>
+#include <limits>
+#include <iostream>
+
+template<class T> void test_popcount( T x )
+{
+    int k = 0;
+    for( T y = x; y; y &= y - 1, ++k );
+
+    BOOST_TEST_EQ( boost::core::popcount( x ), k ) || ( std::cerr << "x: " << +x << std::endl );
+}
+
+int main()
+{
+    {
+        test_popcount( static_cast<unsigned char>( 0 ) );
+        test_popcount( static_cast<unsigned short>( 0 ) );
+        test_popcount( static_cast<unsigned int>( 0 ) );
+        test_popcount( static_cast<unsigned long>( 0 ) );
+        test_popcount( static_cast<unsigned long long>( 0 ) );
+    }
+
+    boost::detail::splitmix64 rng;
+
+    for( int i = 0; i < 1000; ++i )
+    {
+        boost::uint64_t x = rng();
+
+        test_popcount( static_cast<unsigned char>( x ) );
+        test_popcount( static_cast<unsigned short>( x ) );
+        test_popcount( static_cast<unsigned int>( x ) );
+        test_popcount( static_cast<unsigned long>( x ) );
+        test_popcount( static_cast<unsigned long long>( x ) );
+    }
+
+    return boost::report_errors();
+}