threading_backend.h

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
 
#ifndef TVM_RUNTIME_THREADING_BACKEND_H_
#define TVM_RUNTIME_THREADING_BACKEND_H_
 
#include <tvm/runtime/c_backend_api.h>
 
#include <algorithm>
#include <functional>
#include <memory>
#include <vector>
 
#if defined(__linux__) || defined(__ANDROID__)
#if defined(__ANDROID__)
#ifndef CPU_SET
#define CPU_SETSIZE 1024
#define __NCPUBITS (8 * sizeof(uint64_t))
typedef struct {
  uint64_t __bits[CPU_SETSIZE / __NCPUBITS];
} cpu_set_t;
 
#define CPU_SET(cpu, cpusetp) \
  ((cpusetp)->__bits[(cpu) / __NCPUBITS] |= (1UL << ((cpu) % __NCPUBITS)))
#define CPU_ZERO(cpusetp) memset((cpusetp), 0, sizeof(cpu_set_t))
#define CPU_ISSET(cpu, cpusetp)    \
  (1UL << ((cpu) % __NCPUBITS)) == \
      ((cpusetp)->__bits[(cpu) / __NCPUBITS] & (1UL << ((cpu) % __NCPUBITS)))
#define CPU_EQUAL(left, right) (memcmp(&left, &right, sizeof(cpu_set_t)) == 0)
 
#endif
#endif
#endif
 
namespace tvm {
namespace runtime {
namespace threading {
 
class ThreadGroup {
 public:
  class Impl;
 
  TVM_DLL ThreadGroup(int num_workers, std::function<void(int)> worker_callback,
                      bool exclude_worker0 = false);
  TVM_DLL ~ThreadGroup();
 
  TVM_DLL void Join();
 
  enum AffinityMode : int {
    kBig = 1,
    kLittle = -1,
    /*Different threads will get different affinities.*/
    kSpecifyOneCorePerThread = -2,
    /*All threads will get the same core group affinity.*/
    kSpecifyThreadShareAllCore = -3,
  };
  TVM_DLL int Configure(AffinityMode mode, int nthreads, bool exclude_worker0,
                        std::vector<unsigned int> cpus = {});
 
 private:
  Impl* impl_;
};
 
TVM_DLL void Yield();
TVM_DLL int MaxConcurrency();
TVM_DLL void SetMaxConcurrency(int value);
TVM_DLL void ResetThreadPool();
 
TVM_DLL void Configure(tvm::runtime::threading::ThreadGroup::AffinityMode mode, int nthreads,
                       std::vector<unsigned int> cpus);
 
TVM_DLL int32_t NumThreads();
 
}  // namespace threading
 
template <typename T>
inline void parallel_for_with_threading_backend(T flambda, int64_t begin, int64_t end);
 
namespace detail {
 
// The detailed implementation of `parallel_for_with_threading_backend`.
// To avoid template expansion, the implementation cannot be placed
// in .cc files.
 
template <typename T>
struct ParallelForWithThreadingBackendLambdaInvoker {
  static int TVMParallelLambdaInvoke(int task_id, TVMParallelGroupEnv* penv, void* cdata) {
    int num_task = penv->num_task;
    // Convert void* back to lambda type.
    T* lambda_ptr = static_cast<T*>(cdata);
    // Invoke the lambda with the task id (thread id).
    (*lambda_ptr)(task_id, num_task);
    return 0;
  }
};
 
template <typename T>
inline void parallel_launch_with_threading_backend(T flambda) {
  // Launch the lambda by passing its address.
  void* cdata = &flambda;
  TVMBackendParallelLaunch(ParallelForWithThreadingBackendLambdaInvoker<T>::TVMParallelLambdaInvoke,
                           cdata, /*num_task=*/0);
}
 
}  // namespace detail
 
template <typename T>
inline void parallel_for_with_threading_backend(T flambda, int64_t begin, int64_t end) {
  if (end - begin == 1) {
    flambda(begin);
    return;
  }
 
  auto flaunch = [begin, end, flambda](int task_id, int num_task) {
    // For each thread, do static division and call into flambda.
    int64_t total_len = end - begin;
    int64_t step = (total_len + num_task - 1) / num_task;
    int64_t local_begin = std::min(begin + step * task_id, end);
    int64_t local_end = std::min(local_begin + step, end);
    for (int64_t i = local_begin; i < local_end; ++i) {
      flambda(i);
    }
  };
  // Launch with all threads.
  detail::parallel_launch_with_threading_backend(flaunch);
}
 
}  // namespace runtime
}  // namespace tvm
 
#endif  // TVM_RUNTIME_THREADING_BACKEND_H_