A3: Concurrency exercise..

7 files changed, 845 insertions, 41 deletions

diff --git a/a3/concurrency.cc b/a3/concurrency.cc
index da7b51e..9838212 100644
--- a/a3/concurrency.cc
+++ b/a3/concurrency.cc
@@ -41,6 +41,47 @@ void measure(const std::string& text, Callable c)
 	}
 }
 
+template<typename T>
+std::vector<T> get_random_vector(std::size_t size,
+                                 T min = std::numeric_limits<T>::min(),
+                                 T max = std::numeric_limits<T>::max())
+{
+	std::default_random_engine generator;
+	// Randomly generate T-values from the range [min; max]
+	std::uniform_int_distribution<T> distrib(min, max);
+
+	std::vector<T> v;
+	v.resize(size);
+	for(auto& item : v)
+	{
+		item = distrib(generator);
+	}
+
+	return v;
+}
+
+std::vector<std::string> get_random_strings(std::size_t size,
+                                            std::size_t length,
+                                            char min, char max)
+{
+	std::default_random_engine generator;
+	// Randomly generate T-values from the range [min; max]
+	std::uniform_int_distribution<char> distrib(min, max);
+
+	std::vector<std::string> v;
+	v.resize(size);
+	for(auto& str : v)
+	{
+		str.reserve(length);
+		for(auto i = 0u; i < str.capacity(); ++i)
+		{
+			str += distrib(generator);
+		}
+	}
+
+	return v;
+}
+
 template<typename C, typename T>
 //	requires std::forward_iterator<Iter>
 	requires std:: ranges::input_range<C>
@@ -116,47 +157,6 @@ std::vector<const T*> find_all(const C& v, const T& key, std::size_t n)
 	return res;
 }
 
-template<typename T>
-std::vector<T> get_random_vector(std::size_t size,
-                                 T min = std::numeric_limits<T>::min(),
-                                 T max = std::numeric_limits<T>::max())
-{
-	std::default_random_engine generator;
-	// Randomly generate T-values from the range [min; max]
-	std::uniform_int_distribution<T> distrib(min, max);
-
-	std::vector<T> v;
-	v.resize(size);
-	for(auto& item : v)
-	{
-		item = distrib(generator);
-	}
-
-	return v;
-}
-
-std::vector<std::string> get_random_strings(std::size_t size,
-                                            std::size_t length,
-                                            char min, char max)
-{
-	std::default_random_engine generator;
-	// Randomly generate T-values from the range [min; max]
-	std::uniform_int_distribution<char> distrib(min, max);
-
-	std::vector<std::string> v;
-	v.resize(size);
-	for(auto& str : v)
-	{
-		str.reserve(length);
-		for(auto i = 0u; i < str.capacity(); ++i)
-		{
-			str += distrib(generator);
-		}
-	}
-
-	return v;
-}
-
 int main()
 {
 	{
diff --git a/a3/console.log b/a3/console.log
new file mode 100644
index 0000000..cc6ca55
--- /dev/null
+++ b/a3/console.log
@@ -0,0 +1,136 @@
+Single threaded search for int:
+ 99.0755 ms passed
+ 99.502 ms passed
+ 98.4946 ms passed
+Multi threaded (1) search for int:
+ 100.361 ms passed
+ 101.444 ms passed
+ 99.3357 ms passed
+Multi threaded (2) search for int:
+ 51.6977 ms passed
+ 51.4575 ms passed
+ 51.7779 ms passed
+Multi threaded (3) search for int:
+ 34.7178 ms passed
+ 34.4771 ms passed
+ 34.3003 ms passed
+Multi threaded (4) search for int:
+ 25.9185 ms passed
+ 25.8058 ms passed
+ 25.7757 ms passed
+Multi threaded (5) search for int:
+ 32.3892 ms passed
+ 31.1645 ms passed
+ 32.3938 ms passed
+Multi threaded (6) search for int:
+ 26.9827 ms passed
+ 27.004 ms passed
+ 26.9901 ms passed
+Multi threaded (7) search for int:
+ 23.3415 ms passed
+ 23.2642 ms passed
+ 23.6421 ms passed
+Multi threaded (8) search for int:
+ 21.0321 ms passed
+ 26.3786 ms passed
+ 20.651 ms passed
+Multi threaded (9) search for int:
+ 26.4053 ms passed
+ 26.0672 ms passed
+ 25.8895 ms passed
+Multi threaded (10) search for int:
+ 25.8863 ms passed
+ 29.3205 ms passed
+ 24.2901 ms passed
+Multi threaded (11) search for int:
+ 28.1128 ms passed
+ 27.3005 ms passed
+ 24.1081 ms passed
+Multi threaded (12) search for int:
+ 26.8832 ms passed
+ 26.7973 ms passed
+ 25.3346 ms passed
+Multi threaded (13) search for int:
+ 24.995 ms passed
+ 23.6564 ms passed
+ 24.9819 ms passed
+Multi threaded (14) search for int:
+ 23.1928 ms passed
+ 23.1057 ms passed
+ 23.4752 ms passed
+Multi threaded (15) search for int:
+ 23.096 ms passed
+ 24.1333 ms passed
+ 22.1936 ms passed
+Multi threaded (16) search for int:
+ 24.4629 ms passed
+ 20.9868 ms passed
+ 22.8824 ms passed
+Single threaded search for string:
+ 266.31 ms passed
+ 264.754 ms passed
+ 265.04 ms passed
+Multi threaded (1) search for string:
+ 262.007 ms passed
+ 261.643 ms passed
+ 260.548 ms passed
+Multi threaded (2) search for string:
+ 136.218 ms passed
+ 136.152 ms passed
+ 136.74 ms passed
+Multi threaded (3) search for string:
+ 91.529 ms passed
+ 91.1464 ms passed
+ 91.6109 ms passed
+Multi threaded (4) search for string:
+ 77.8617 ms passed
+ 80.5186 ms passed
+ 68.423 ms passed
+Multi threaded (5) search for string:
+ 76.2207 ms passed
+ 70.712 ms passed
+ 76.2605 ms passed
+Multi threaded (6) search for string:
+ 63.9025 ms passed
+ 63.9237 ms passed
+ 63.8663 ms passed
+Multi threaded (7) search for string:
+ 55.3068 ms passed
+ 55.0763 ms passed
+ 55.4004 ms passed
+Multi threaded (8) search for string:
+ 51.9505 ms passed
+ 50.4089 ms passed
+ 51.307 ms passed
+Multi threaded (9) search for string:
+ 59.1842 ms passed
+ 60.9649 ms passed
+ 61.4107 ms passed
+Multi threaded (10) search for string:
+ 58.4679 ms passed
+ 58.8267 ms passed
+ 57.1795 ms passed
+Multi threaded (11) search for string:
+ 60.2347 ms passed
+ 55.0205 ms passed
+ 61.8008 ms passed
+Multi threaded (12) search for string:
+ 59.427 ms passed
+ 54.7694 ms passed
+ 57.2314 ms passed
+Multi threaded (13) search for string:
+ 57.0578 ms passed
+ 56.0438 ms passed
+ 52.5656 ms passed
+Multi threaded (14) search for string:
+ 54.9454 ms passed
+ 53.1546 ms passed
+ 56.7422 ms passed
+Multi threaded (15) search for string:
+ 54.7158 ms passed
+ 55.0651 ms passed
+ 56.6704 ms passed
+Multi threaded (16) search for string:
+ 50.825 ms passed
+ 55.0096 ms passed
+ 53.4777 ms passed
diff --git a/a3/exercise.tex b/a3/exercise.tex
new file mode 100644
index 0000000..92e5cc4
--- /dev/null
+++ b/a3/exercise.tex
@@ -0,0 +1,110 @@
+\title{A3: Concurrency}
+\input{preamble.tex}
+In this assignment experiments with doing multithreaded searches in
+containers is performed measured and evaluated.
+
+A few attempts at using concepts for some generalized utility
+functions were made and any comments on the (success or lack thereof)
+on these is highly welcome.
+
+The utility functions are the following:
+\begin{itemize}
+\item The \texttt{measure} function and \texttt{Measure} class from
+  previous assignment, doing time measurement and printing the result.
+\item \texttt{get\_random\_vector} which is a templated function that
+  generates and returns a \texttt{std::vector} of a given size with
+  random values in a specified range.
+\item \texttt{get\_random\_strings} which is a function that generates
+  a \texttt{std::vector} og \texttt{std::string}s of a specified
+  length (all the same length) and with random characters picked from
+  a specified range.
+\end{itemize}
+
+The two generator function are likely far more generalized than
+necessary for this exercise, but the idea is to be able to re-use them
+in future exercises, facilitate good readability of the code in the
+\texttt{main} function and play around a bit with concepts.
+
+\bigskip
+
+The first task is to implement a \texttt{find\_all} function that
+returns a \texttt{std::vector<T*>} of found keys in the supplied input
+container.
+As the wording later in the assignment are ``How large must the
+\textbf{array} be,...'', I decided to make the function work on any
+container type by using the range concept instead of hard-coding it to
+\texttt{std::vector}. Any comments on how this has been done are more
+than welcome.
+At the top of the \texttt{main} function there are two examples of
+other container types I tried using with the functions (commented
+out); \texttt{std::array} and c-style array.
+
+\bigskip
+
+The next task was to write a 10-way parallel \texttt{find\_all} with
+the same functionality as the first one but executing 10 threads
+working on a 10th of the input container.
+I generalized this to \textit{n} threads in my first implementation (I
+hadn't seen that this was a requirement further down in the
+assignment).
+
+The threads are running through \texttt{std::async(std::launch::async, ...)}
+and each thread is initially blocking on a
+\texttt{std::condition\_variable} to make it possible to start
+measureing the execution time only after spawning all the threads.
+Each threads then simply executes the initial non-threaded
+implementation of \texttt{find\_all} with their respective sub-ranges
+and returns their result in each its own \texttt{std::vector<T*>}
+through a \texttt{std::future}.
+Finally all sub-range results are accumulated in on
+\texttt{std::vector<T*>} and returned to the \texttt{main} function.
+
+\bigskip
+
+Vectors of 10 million elements of both \texttt{int}s and
+\texttt{std::string}s are used for the tests and each of the two are
+tested in single-threaded \texttt{find\_all}, and multithreaded
+\texttt{find\_all} with 1 through 16 threads.
+
+Each run is timed and printed to the console and since the output is
+rather large is is attached in the \texttt{console.log} file alongside
+this report.
+
+\bigskip
+
+The machine used for the tests is an Intel i7 with 4 cores, each hyper
+threaded, so 8 ``virtual'' cores, each sharing parts of the cache with
+one of the others.
+
+\bigskip
+
+Looking at the results for \texttt{int}; non-threaded search took
+about 100ms and (not surprising really) so did the 1-threaded search. From
+there the search performed better and better flattening out.
+
+\begin{figure}
+  \caption{\label{ints} Showing execution times vs number of threads
+    searching for \texttt{int}s.}
+  \includegraphics[scale=0.55]{a3/int.pdf}
+\end{figure}
+
+\begin{figure}
+  \caption{\label{strings} Showing execution times vs number of threads
+    searching for \texttt{std::string}s.}
+  \includegraphics[scale=0.55]{a3/string.pdf}
+\end{figure}
+
+As seen in figure \ref{ints} the performance increase stagnates
+already at around 4 threads, suggesting that the memory pipeline/cache
+is a bottleneck that makes the threads do a lot of waiting for data
+rather than execute instructions.
+
+\bigskip
+
+Similar results are seen on the \texttt{std::string}
+searches. Although there seem to be more calculation going on so the
+memory/cache bottleneck is less dominating. This can be seen in figure
+\ref{strings} the graph seem to flatten out at bit at around 4 threads
+but keeps performing better until all 8 hyperthreads are active.
+
+\end{document}
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diff --git a/a3/int.pdf b/a3/int.pdf
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index 0000000..79de095
--- /dev/null
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diff --git a/a3/string.eps b/a3/string.eps
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diff --git a/a3/string.pdf b/a3/string.pdf
new file mode 100644
index 0000000..af4cfc2
--- /dev/null
+++ b/a3/string.pdf