Parallel STL is an implementation of the Technical Specification for C++ Extensions for Parallelism for both CPU and GPU with SYCL Heterogeneous C++ language. This technical specification describes a set of requirements for implementations of an interface that C++ programs may use to invoke algorithms with parallel execution. In practice, this specification allows users to specify execution policies to traditional STL algorithms which will enable the execution of those algorithms in parallel. The various policies can specify different kinds of parallel execution. For example,