Extensions for parallelism

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Technical specifications

Filesystem library (filesystem TS)

Library fundamentals (library fundamentals TS)

Library fundamentals 2 (library fundamentals 2 TS)

Extensions for parallelism (parallelism TS)

Extensions for concurrency (concurrency TS)

Concepts (concepts TS)

Ranges (ranges TS)

Special mathematical functions (special math TR)

 

Extensions for parallelism

Execution policies

parallel::execution_policy

parallel::sequential_execution_policyparallel::parallel_execution_policyparallel::parallel_vector_execution_policy

parallel::seqparallel::parparallel::par_vec

Parallel algorithms

Parallel exceptions

parallel::exception_list

Parallelized version of existing algorithms

New algorithms

parallel::for_eachparallel::for_each_n

parallel::reduce

parallel::exclusive_scan

parallel::inclusive_scan

parallel::transform_reduce

parallel::transform_exclusive_scan

parallel::transform_inclusive_scan

 

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_policyparallel_execution_policyparallel_vector_execution_policy	execution policy types (class)
seqparpar_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 ith input element from the ith sum (function template)
inclusive_scan	similar to std::partial_sum, includes the ith input element in the ith 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)