From d4c7424fedc83079d0c460d65f7daa8308ff969c Mon Sep 17 00:00:00 2001
From: Bent Bisballe Nyeng <deva@aasimon.org>
Date: Wed, 26 Jul 2023 08:18:36 +0200
Subject: A2: WIP

---
 a2/measurement.cc | 159 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 a2/measurement.cc

(limited to 'a2/measurement.cc')

diff --git a/a2/measurement.cc b/a2/measurement.cc
new file mode 100644
index 0000000..cf90d52
--- /dev/null
+++ b/a2/measurement.cc
@@ -0,0 +1,159 @@
+#if 0
+import <chrono>;
+import <vector>;
+import <iostream>;
+import <algorithm>;
+import <string>;
+import <thread>;
+#else
+#include <chrono>
+#include <vector>
+#include <iostream>
+#include <algorithm>
+#include <string>
+#include <thread>
+#include <random>
+#endif
+
+class Measure
+{
+public:
+	Measure()
+		: start(std::chrono::high_resolution_clock::now())
+	{
+	}
+
+	~Measure()
+	{
+		auto end = std::chrono::high_resolution_clock::now();
+		std::chrono::duration<double> delta = end - start;
+		std::cout << " " << delta.count() * 1000 << " ms passed" << std::endl;
+	}
+
+	std::chrono::time_point<std::chrono::high_resolution_clock> start{};
+};
+
+template<typename Callable>
+void measure(const std::string& text, Callable c)
+{
+	std::cout << text << ":\n";
+
+	for(int i = 0; i < 3; ++i)
+	{ // RAII timed scoped
+		Measure m;
+		c();
+	}
+}
+
+
+int main()
+{
+	using namespace std::chrono_literals;
+
+	// Sanity check measurement mechanism
+	measure("Sanity check (sleep 100ms):",
+	        []()
+	        {
+		        std::this_thread::sleep_for(100ms);
+	        });
+
+	// std::find() on a vector<int>:
+	// Use a vector large enough to get meaningful values on your machine
+	// (1,000,000 elements are likely not enough). Measure the time needed to
+	//  * Find the 7 in the middle of a vector<int> where all other elements are
+	//    not 7.
+	{
+		std::vector<int> v(1'000'000, 42); // one million items with the int 42
+		v[v.size() / 2] = 7; // set middle item to 7
+		measure("std::find 7 in the middle",
+		        [&v]()
+		        {
+			        std::find(v.begin(), v.end(), 7);
+		        });
+	}
+
+	//  * Try to find a 7 in a vector<int> where no element is 7
+	{
+		std::vector<int> v(1'000'000, 42); // one million items with the int 42
+		measure("std::find 7 not there",
+		        [&v]()
+		        {
+			        std::find(v.begin(), v.end(), 7);
+		        });
+	}
+
+	// std::find_if() on a vector<int>:
+	// Use a vector large enough to get meaningful values on your machine.
+	// Measure the time needed to
+	//  * Find the x < 7 in the middle of a vector<int> where all other elements
+	//    are >= 7.
+	{
+		std::vector<int> v(1'000'000, 42); // one million items with the int 42
+		v[v.size() / 2] = 5; // set middle item to 5
+		measure("std::find_if x < 7 in the middle",
+		        [&v]()
+		        {
+			        std::find_if(v.begin(), v.end(), [](int x){ return x < 7;});
+		        });
+	}
+
+	//  * Try to find an x < 7 in a vector<int> where all elements are >= 7.
+	{
+		std::vector<int> v(1'000'000, 42); // one million items with the int 42
+		measure("std::find_if x < 7 not there",
+		        [&v]()
+		        {
+			        std::find_if(v.begin(), v.end(), [](int x){ return x < 7;});
+		        });
+	}
+
+	// std::find() on a vector<std::string>:
+	// Generate a vector<string> containing 1,000,000 random 20-letter strings
+	// (don't bother timing this).
+	{
+		std::default_random_engine generator;
+		// Randomly generate characters from the range  [A;Z]
+		std::uniform_int_distribution<char> distrib('A', 'Z');
+
+		std::vector<std::string> vs;
+		vs.resize(1'000'000);
+		for(auto &str: vs)
+		{
+			str.reserve(20);
+			for(auto i = 0u; i < str.capacity(); ++i)
+			{
+				str += distrib(generator);
+			}
+		}
+
+		std::string needle(20, 'X');
+
+		// Measure the time needed to
+		//  * Try to find XXXXXXXXXXXXXXXXXXXX (20 Xs) in that vector using
+		//    std::find().
+		measure("Find " + needle + " (not there)",
+		        [&]()
+		        {
+			        if(std::find(vs.begin(), vs.end(), needle) != std::end(vs))
+			        {
+				        std::cout << "That was unexpected!\n";
+			        }
+		        });
+
+		//  * Was it there? Unlikely, but if so, try with another value.
+		//    Alternatively (optional), ensure you never generate
+		//    XXXXXXXXXXXXXXXXXXXX in the first place.
+		//
+		//  * Place XXXXXXXXXXXXXXXXXXXX (or whatever value is not present) in the
+		//    middle and find it using std::find().
+		vs[vs.size() / 2] = needle;
+		measure("Find " + needle + " (in the middle)",
+		        [&]()
+		        {
+			        if(std::find(vs.begin(), vs.end(), needle) == std::end(vs))
+			        {
+				        std::cout << "That was unexpected!\n";
+			        }
+		        });
+	}
+}
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