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Author: diehlpk

sources/modules/concurrency-parallelism/async-programming.md

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+## Module name: Asynchronous programming
+
+_Skeleton descriptions are typeset in italic text,_
+_so please don't remove these descriptions when editing the topic._
+
+### Overview
+
+_Provides a short natural language abstract of the module’s contents._
+_Specifies the different levels of teaching._
+
+------------------------------------------------------------------------
+Level             Objective
+----------------- ------------------------------------------------------
+Foundational      --- Knowledge about build systems
+
+Main              --- Usage of build system to compile a executable
+
+Advanced          --- Add external libraries as a dependencies  
+
+------------------------------------------------------------------------
+
+### Motivation
+
+_Why is this important?_
+_Why do we want to learn/teach this topic?_
+
+* Asynchronous programming allows for non-blocking functions launches and enables that functions are executed asynchronoulsy.
+* Asynchronous programming is one form of parallism and concurrency included in the C++ standard
+
+### Topic introduction
+
+_Very brief introduction to the topic._
+
+Build systems are used to configure, build, and install complex C++ projects. 
+
+
+### Foundational: Knowledge about build systems
+
+#### Background/Required Knowledge
+
+A student: 
+* Should know [lambdas](../functions/lambdas.md)
+
+#### Student outcomes
+
+_A list of things "a student should be able to" after the curriculum._
+_The next word should be an action word and testable in an exam._
+_Max 5 items._
+
+A student should be able to:
+
+1. To explain what asynchronous programming is
+2. To explain what a futures and promise are
+
+#### Caveats
+
+_This section mentions subtle points to understand, like anything resulting in
+implementation-defined, unspecified, or undefined behavior._
+
+None
+
+#### Points to cover
+
+_This section lists important details for each point._
+
+* Mention how to launch a function or lambda asynchronously using `std::async`  
+* Mention how to use a `std::future` as a place holder for the result
+
+### Main: Launch functions asynchronous and obtain the results
+
+#### Background/Required Knowledge
+
+* All of the above.
+
+#### Student outcomes
+
+A student should be able to:
+
+1. Do define a function or lambda for the computational task
+2. Launch the function or lambda asynchronous and obtain the results
+
+#### Caveats
+
+The concept of asyncrhonous programming is no easy digestiable for most students.
+
+
+#### Points to cover
+
+* The header `<future>` needs to be includes
+* The return type of the function or lambda will the the template type of the future
+* The first argument of `std::async` is the function or lambda and after that all arguments are providesd
+
+Example using a function
+```
+void print_square(double a)
+{
+ std::cout << "Result=" << a * a << std::endl;
+}
+
+std::future<void> f = std::async(print,5.0);
+// We could do other work here
+f.get()
+```
+
+Example using lambdas
+```
+// Compute the sum
+std::future<double> f1 = std::async([](double a, double b){ return a + b;});
+// Compute the square
+std::future<double> f2 = std::async([](double a){ return a * a;});
+
+// Gather the results and add them up
+double res = f1.get() + f2.get();
+```
+
+### Advanced
+
+_These are important topics that are not expected to be covered but provide
+guidance where one can continue to investigate this topic in more depth._
+
+* How to build libraries 
+* How to have external libraries be downloaded during the build process
+* Mention that build systems provide support for unit testing
+