Extensions for parallelism

The C++ Extensions for Parallelism, ISO/IEC TS 19570:2015 defines the following new components for the C++ standard library:

Execution policies

The parallelism TS describes three execution policies: sequential , parallel , and parallel+vector , and provides corresponding execution policy types and objects. Users may select an execution policy statically by invoking a parallel algorithm with the an execution policy object of the corresponding type, or dynamically by using the type-erasing execution_policy class.

Implementations may define additional execution policies as an extension. The semantics of parallel algorithms invoked with an execution policy object of implementation-defined type is implementation-defined.

Defined in header <experimental/execution_policy>
sequential_execution_policy parallel_execution_policy parallel_vector_execution_policy	execution policy types (class)
seq par par_vec	global execution policy objects (constant)
execution_policy	dynamic execution policy (class)
is_execution_policy	test whether a class represents an execution policy (class template)

Exception lists

Defined in header <experimental/exception_list>
exception_list	exceptions raised during parallel executions (class)

Parallelized versions of existing algorithms

The TS provides parallelized versions of the following 69 algorithms from <algorithm>, <numeric> and <memory>:

New algorithms

Defined in header <experimental/algorithm>
for_each	similar to std::for_each except returns void (function template)
for_each_n	applies a function object to the first n elements of a sequence (function template)
Defined in header <experimental/numeric>
reduce (parallelism TS)	similar to std::accumulate , except out of order (function template)
exclusive_scan	similar to std::partial_sum , excludes the i th input element from the i th sum (function template)
inclusive_scan	similar to std::partial_sum , includes the i th input element in the i th sum (function template)
transform_reduce (parallelism TS)	applies a functor, then reduces out of order (function template)
transform_exclusive_scan	applies a functor, then calculates exclusive scan (function template)
transform_inclusive_scan	applies a functor, then calculates inclusive scan (function template)