Quick Start: Execution

Introduction

ZPC offers parallel execution policy classes with a consistent interface, each corresponding to a certain compute back-end marked by execspace_e. Currently there are execspace_e::host, execspace_e::cuda, execspace_e::openmp for parallel executions on CPU and GPUs.

Every execution policy class should provide implementations for the following parallel primitives:

• for_each
• reduce
• scan (exclusive and inclusive)
• radix_sort (and its variant radix_sort_pair)
• merge_sort (and its variant merge_sort_pair)

A policy class object can be configured at runtime. Common settings include:

• sync(bool): specifies whether its execution is synchronous to the host thread that issues the execution when complete.
• profile(bool): specifies whether to profile and print the timings of the executions issues.

For cuda execution policy, additional settings include device(ProcID), etc.

Note that currently host-side radix sort does not support floating points yet.

Usage

To utilize the execution policy for fast and convenient parallel execution,

#include "zensim/execution/ExecutionPolicy.hpp"
// or #include "zensim/cuda/execution/ExecutionPolicy.cuh"
// or #include "zensim/omp/execution/ExecutionPolicy.hpp"

Vector<T> someContainer{...};
constexpr execspace_e space = ...;
auto execPol = par_exec(tag<space>);
execPol.sync(true).profile(true); // these are the default options
// 1
execPol(someContainer, []ZS_LAMBDA(T &v) { 
  // operator on v
});
// 2
execPol(range(someContainer.size()), [vec = proxy<space>(someContainer)]ZS_LAMBDA(int i) { 
  // operator on vec(i)
});
// 3
for_each(execPol, someContainer, []ZS_LAMBDA(T &v) { 
  // operator on v
});

Error Handling

All host-side computations expects programmers to use try-catch idiom to handle exceptions thrown from the execution of the functor. Therefore it is programmer's responsibility to handle it manually.

All device(cuda)-side execution errors are dealt by giving back error codes, which is automatically handled by ZPC.

Advanced Usage

to be done.