From cppreference.com
The C++ Extensions for Parallelism Version 2, ISO/IEC TS 19570:2018 defines the following new components for the C++ standard library:
Parallel exceptions
Execution policies
Parallel algorithms
Task Block
(parallelism TS v2)
data-parallel vector type
(class template)
(parallelism TS v2)
data-parallel type with the element type bool
(class template)
Feature test macros
Defined in header
__cpp_lib_experimental_parallel_task_block
a value of at least 201711 indicates that the task block functionality is supported
(macro constant)Defined in header
__cpp_lib_experimental_execution_vector_policy
a value of at least 201711 indicates that the vector and wavefront policies are supported
(macro constant)Defined in header
__cpp_lib_experimental_parallel_for_loop
a value of at least 201711 indicates that the for_loop class of algorithms is supported
(macro constant)Defined in header
__cpp_lib_experimental_parallel_simd
a value of at least 201803 indicates that the data-parallel types library is supported
(macro constant)