From f483c1725ddb5e082edf7b0cdb866270bad2c134 Mon Sep 17 00:00:00 2001
From: Vahagn Khachatryan <vahagn.khachatryan@gmail.com>
Date: Fri, 5 Jul 2013 00:19:25 +0400
Subject: [PATCH] memory_benchmark.cpp

---
 memory_benchmark.cpp | 108 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 memory_benchmark.cpp

diff --git a/memory_benchmark.cpp b/memory_benchmark.cpp
new file mode 100644
index 0000000..8c7af52
--- /dev/null
+++ b/memory_benchmark.cpp
@@ -0,0 +1,108 @@
+/* Check cf5-opt.vim defs.
+VIM: let g:lcppflags="-std=c++11 -O2 -pthread"
+VIM: let g:wcppflags="/O2 /EHsc /DWIN32"
+VIM: let g:cppflags=g:Iboost
+VIM: let g:ldflags=g:Lboost
+VIM: let g:ldlibpath=g:Bboost
+VIM: let g:argv=""
+VIM-: let g:cf5output=0
+*/
+#include <iostream>
+#include <iomanip>
+#include <exception>
+#include <chrono>
+#include <algorithm>
+
+typedef long long duration_type;
+static const size_t ce = 1024L*1024L*1024L;
+
+duration_type scan_read( char * p, const size_t c, const size_t s )
+{
+	auto b = std::chrono::high_resolution_clock::now();
+	
+	int sum = 0;
+	char * qe = p+c;
+	for ( int n =0, ne=ce/c; n < ne; ++n ) 
+		for ( size_t i = 0; i < s; ++i )
+			for ( char * q = p+i; q < qe; q+=s )
+				sum += *q;
+	volatile int no_optimization = sum;
+	auto e = std::chrono::high_resolution_clock::now();
+	return std::chrono::nanoseconds(e-b).count();
+}
+
+duration_type scan_write( char * p, const size_t c, const size_t s )
+{
+	int a = rand();
+
+	auto b = std::chrono::high_resolution_clock::now();
+	
+	char * qe = p+c;
+	for ( int n =0, ne=ce/c; n < ne; ++n ) 
+		for ( size_t i = 0; i < s; ++i )
+			for ( char * q = p+i; q < qe; q+=s )
+				*q = a;
+	
+	auto e = std::chrono::high_resolution_clock::now();
+	return std::chrono::nanoseconds(e-b).count();
+}
+
+template <class F>
+void test_steps( F f , char * p, const size_t c, char * nm )
+{
+	f( p, c, 1 ); // First run ignore.
+
+	std::cout << std::setw(10) << "steps";
+	std::cout << std::setw(16) << nm;
+	std::cout << std::setw(16) << nm;
+	std::cout << std::setw(16) << nm;
+	std::cout << std::setw(16) << "average";
+	std::cout << std::setw(16) << "deviation" << std::endl;
+
+	for ( size_t s = 1; s < c; s<<=1 )
+	{
+		std::cout << std::setw(10) << s << std::flush;
+		auto d1 = f( p, c, s );
+		std::cout << std::setw(16) << d1 << std::flush;
+		auto d2 = f( p, c, s );
+		std::cout << std::setw(16) << d2 << std::flush;
+		auto d3 = f( p, c, s );
+		std::cout << std::setw(16) << d3 << std::flush;
+		auto a = (d1+d2+d3)/3;
+		std::cout << std::setw(16) << a;
+		auto dev = (std::abs(d1-a)+std::abs(d2-a)+std::abs(d3-a))/3;
+		std::cout << std::setw(16) << dev << std::endl;
+	}
+}
+
+void test_workingset( const size_t c )
+{
+	char * p = (char*)malloc( c );
+	
+	std::cout << "Working set " << c << std::endl ;
+	test_steps( scan_read, p, c, "read" );
+	test_steps( scan_write, p, c, "write" );
+}
+
+int main ( void )
+{try{
+
+
+	for ( size_t c = 4096; c <= ce; c <<=1 )
+		test_workingset( c );
+
+	return 0;
+}
+catch ( const std::exception& e )
+{
+	std::cerr << std::endl
+			<< "std::exception(\"" << e.what() << "\")." << std::endl;
+	return 2;
+}
+catch ( ... )
+{
+	std::cerr  << std::endl
+			<< "unknown exception." << std::endl;
+	return 1;
+}}
+