THE STL AND YOULeveraging the C++ Standard Template Library for great good!

A sprinkle of Thrust as well

OVERVIEW

• STL?

• Containers

• Iterators

• Algorithms

• Functional fun.

STL

• A very large body of data structures and algorithms

•Most of the primal data structures

• Stacks, Queues, Lists, Hashmaps(C++11) and more

• Algorithms which operate on these data structures

• Partitioning, Counting, Sorting and more

STL

• Split into 4 sort of groups

• Containers

• Iterators

• Algorithms

• Functors

• Function objects

STL

• Unless you are using an extremely old compiler and libc++ you have most of it

•Newer C++11 features may or may not be implemented depending on your tool chain

• It will be noted when something is only for the new kids on the block

• Influenced the standard library

QUESTIONS

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CONTAINERS

• They contain data.

CONTAINERS

• Just kidding...

• Used to organize data in a regular way

• Sequential containers

• Associative containers

• Unordered containers(C++11)

CONTAINERS

•We will be primarily focusing on sequential containers

• Thrust provides only a single sequential container

SEQUENTIAL CONTAINERS

• std::vector

• a dynamically sized array

• std::list

• generally a doubly linked list

• std::deque

• a double ended queue

STD::VECTOR

• The container we are interested in

• Thrust provides a vector implementation for the GPU

STD::VECTOR

• Superficially very similar to a plain jane array

• foo[ idx ]

• Grows dynamically

• Reallocations tend to be 2x the previous capacity

• Presizing can be important depending on use

STD::VECTOR

• std::vector<int>

• The T in STL

• The following page is from the excellent http://en.cppreference.com/w/cpp

• Replace the en with zh for a handy Chinese reference

STD::VECTOR

STD::VECTOR

•Once created add elements using push_back(ele) or insert(it, ele)

• These will cause resizing events if needed

• using foo[ idx ] = bar will not

STD::VECTOR

• Request the size of vector with size() and the capacity with capacity()

• Size(red) vs Capacity(black)

STD::VECTOR

• Iterating through the elements can be done with a for loop like the arrays you are probably used to.

• There is are better ways...

CONTAINERS

• The interface for containers is largely similar

• Take the time to get to know them

•maps and vectors probably the most used.

HEADERS

• #include<vector>

• #include<stack>

• ...etc

QUESTIONS

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ITERATORS

• Classes of iterators provide guaranties about how elements can be accessed

ITERATORS

•Many different classes

• Important when considering performance and which algorithms to use

ITERATORS

ITERATORS

• http://en.cppreference.com/w/cpp/concept/Iterator

• an example of the requirements for a class of iterators

ITERATOR

• The basics

• Acts like a pointer

• *it

• it++

ITERATORS

•Other operators have a wider range of operators

• See the documentation

QUESTIONS

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GETTING AN ITERATOR

• foo.begin()

• all containers except the containers built on top of other containers(stack, queue, priority_queue)

• also foo.end()

• foo.rbegin()

• foo.cbegin() foo.crbegin() (C++11)

ITERATORS

• From there you can use it!

• for( auto it = foo.begin(); it != foo.end(); ++it)

• for( auto it : foo ) (C++11)

CAVEATS

• Some functions or actions invalidate iterators

• Typically anything that could cause resizing of the container or reorder of the elements within the operator

QUESTIONS

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