The files for this are on Github.
To check out the repository run:
git clone https://github.com/EPCCed/2019-04-16-ModernCpp.git.git
cd 2019-04-16-ModernCpp/practicals/01
The array is a fundamental data structure, especially for processing large amounts of data, as it allows the system to take advantage of the cache hierarchy.
Recall the array examples from the lecture - in
2019-04-16-ModernCpp/practicals/-array is a basic implementation and
a (hopefully) working test program.
Compile this and run it for a few problem sizes. What is the scaling?
We need to take a decision about copying - do we wish to allow implicit copying which for large arrays is very slow? If not, should we add an explicit method to do this? What would its signature be? How would we tell the compiler not to allow this?
While we’ve taken an RAII approach here, it comes with some overhead: we had to implement (or delete) five functions.
A more idiomatic approach is to wrap the resource into a class that does nothing but manage a resource, then it can be used elsewhere and the compiler will produce correct implicit constructors, destructor and assignment operators with no boilerplate code!
See one of the below for an in-depth discussion:
Fortunately the standard library includes several “smart pointers” that
will do this for you for memory! They can be accessed using the
<memory> header.
They are:
std::unique_ptr - this uniquely owns the pointed-to object. The
object is deleted (can be customised) when the smart pointer
destructs or you assign a new value. You cannot copy a unique_ptr.
This should be your default pointer type!
std::shared_ptr - this shares ownership of the pointed-to object.
All the child shared_ptrs point to the same object. The object
will be deleted when all the pointers are either destructed or
assigned a new value.
std::weak_ptr - much like a shared_ptr but it doesn’t own a
share of the object. It can become invalid. Used to break reference
cycles.
(There also exists a std::auto_ptr. This is deprecated and has been
removed from C++17, so do not use it.)
Have a look at the reference
and re-implement Array using either a unique or shared pointer.