diff options
Diffstat (limited to 'a2')
| -rw-r--r-- | a2/Makefile | 15 | ||||
| -rw-r--r-- | a2/exercise.tex | 10 | ||||
| -rw-r--r-- | a2/measurement.cc | 159 |
3 files changed, 184 insertions, 0 deletions
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"; + } + }); + } +} |