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/Makefile | 15 ++++++
a2/exercise.tex | 10 ++++
a2/measurement.cc | 159 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 184 insertions(+)
create mode 100644 a2/Makefile
create mode 100644 a2/exercise.tex
create mode 100644 a2/measurement.cc
(limited to 'a2')
diff --git a/a2/Makefile b/a2/Makefile
new file mode 100644
index 0000000..74f52b2
--- /dev/null
+++ b/a2/Makefile
@@ -0,0 +1,15 @@
+all: measurement
+
+gcm.cache: Makefile
+ rm -Rf gcm.cache
+# g++ -std=c++20 -fmodules-ts -x c++-system-header chrono
+# g++ -std=c++20 -fmodules-ts -x c++-system-header vector
+# g++ -std=c++20 -fmodules-ts -x c++-system-header iostream
+# g++ -std=c++20 -fmodules-ts -x c++-system-header algorithm
+# g++ -std=c++20 -fmodules-ts -x c++-system-header string
+# g++ -std=c++20 -fmodules-ts -x c++-system-header thread
+
+measurement: measurement.cc Makefile
+#gcm.cache
+# g++ -Wall -Werror -Wextra -Wconversion -std=c++20 -fmodules-ts measurement.cc -o measurement
+ g++ -O2 -Wall -Werror -Wextra -Wconversion -std=c++20 measurement.cc -o measurement
diff --git a/a2/exercise.tex b/a2/exercise.tex
new file mode 100644
index 0000000..4615e24
--- /dev/null
+++ b/a2/exercise.tex
@@ -0,0 +1,10 @@
+\title{A2: Measurement}
+\input{preamble.tex}
+
+I got some really wierd behaviour from
+\texttt{std::this\_thread::sleep\_for()} and even a crash and ended up
+having to go back to using \texttt{\#include} instead of modules, which
+solved the issues.
+
+
+\end{document}
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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