Compute Library
 22.08
barrier.hpp
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24 #pragma once
25 
26 #ifndef NO_MULTI_THREADING
27 
28 #include <atomic>
29 
30 namespace arm_gemm {
31 
32 class barrier {
33 private:
34  unsigned int m_threads;
35 
36  std::atomic<unsigned int> m_waiters;
37  std::atomic<unsigned int> m_leavers;
38 
39 public:
40  barrier(unsigned int threads) : m_threads(threads), m_waiters(0), m_leavers(0) { }
41 
42  /* This isn't safe if any thread is waiting... */
43  void set_nthreads(unsigned int nthreads) {
44  m_threads = nthreads;
45  }
46 
47  void arrive_and_wait() {
48  m_waiters++;
49 
50  while (m_waiters != m_threads) {
51  ; /* spin */
52  }
53 
54  unsigned int v = m_leavers.fetch_add(1);
55 
56  if (v == (m_threads - 1)) {
57  m_waiters -= m_threads;
58  m_leavers = 0;
59  } else {
60  while (m_leavers > 0) {
61  ; /* spin */
62  }
63  }
64  }
65 };
66 
67 } // namespace arm_gemm
68 
69 #else
70 
71 namespace arm_gemm {
72 
73 class barrier {
74 public:
75  barrier(unsigned int) { }
76 
77  void arrive_and_wait() { }
78  void set_nthreads(unsigned int ) { }
79 };
80 
81 } // namespace arm_gemm
82 
83 #endif
barrier(unsigned int threads)
Definition: barrier.hpp:40
void arrive_and_wait()
Definition: barrier.hpp:47
void set_nthreads(unsigned int nthreads)
Definition: barrier.hpp:43