[execpol.general]

# 26 Algorithms library [[algorithms]](./#algorithms)

## 26.3 Parallel algorithms [[algorithms.parallel]](algorithms.parallel#execpol.general)

### 26.3.6 Execution policies [[execpol]](execpol#general)

#### 26.3.6.1 General [execpol.general]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L636)

Subclause [[execpol]](execpol "26.3.6 Execution policies") describes classes that are [*execution policy*](#def:execution_policy "26.3.6.1 General [execpol.general]") types[.](#1.sentence-1)

An
object of an execution policy type indicates the kinds of parallelism allowed
in the execution of an algorithm and expresses the consequent requirements on
the element access functions[.](#1.sentence-2)

Execution policy types are declared in header [<execution>](execution.syn#header:%3cexecution%3e "33.4 Header <execution> synopsis [execution.syn]")[.](#1.sentence-3)

[*Example [1](#example-1)*: using namespace std;
vector<int> v = /* ... */;

// standard sequential sort sort(v.begin(), v.end());

// explicitly sequential sort sort(execution::seq, v.begin(), v.end());

// permitting parallel execution sort(execution::par, v.begin(), v.end());

// permitting vectorization as well sort(execution::par_unseq, v.begin(), v.end()); — *end example*]

[*Note [1](#note-1)*:

Implementations can provide additional execution policies
to those described in this document as extensions
to address parallel architectures that require idiosyncratic
parameters for efficient execution[.](#1.sentence-4)

— *end note*]