1 // This file is part of Eigen, a lightweight C++ template library
2 // for linear algebra.
3 //
4 // Copyright (C) 2016 Dmitry Vyukov <dvyukov@google.com>
5 // Copyright (C) 2016 Benoit Steiner <benoit.steiner.goog@gmail.com>
6 //
7 // This Source Code Form is subject to the terms of the Mozilla
8 // Public License v. 2.0. If a copy of the MPL was not distributed
9 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
10 
11 #define EIGEN_USE_THREADS
12 #include "main.h"
13 #include "Eigen/CXX11/ThreadPool"
14 
15 static void test_create_destroy_empty_pool()
16 {
17   // Just create and destroy the pool. This will wind up and tear down worker
18   // threads. Ensure there are no issues in that logic.
19   for (int i = 0; i < 16; ++i) {
20     NonBlockingThreadPool tp(i);
21   }
22 }
23 
24 
25 static void test_parallelism()
26 {
27   // Test we never-ever fail to match available tasks with idle threads.
28   const int kThreads = 16;  // code below expects that this is a multiple of 4
29   NonBlockingThreadPool tp(kThreads);
30   VERIFY_IS_EQUAL(tp.NumThreads(), kThreads);
31   VERIFY_IS_EQUAL(tp.CurrentThreadId(), -1);
32   for (int iter = 0; iter < 100; ++iter) {
33     std::atomic<int> running(0);
34     std::atomic<int> done(0);
35     std::atomic<int> phase(0);
36     // Schedule kThreads tasks and ensure that they all are running.
37     for (int i = 0; i < kThreads; ++i) {
38       tp.Schedule([&]() {
39         const int thread_id = tp.CurrentThreadId();
40         VERIFY_GE(thread_id, 0);
41         VERIFY_LE(thread_id, kThreads - 1);
42         running++;
43         while (phase < 1) {
44         }
45         done++;
46       });
47     }
48     while (running != kThreads) {
49     }
50     running = 0;
51     phase = 1;
52     // Now, while the previous tasks exit, schedule another kThreads tasks and
53     // ensure that they are running.
54     for (int i = 0; i < kThreads; ++i) {
55       tp.Schedule([&, i]() {
56         running++;
57         while (phase < 2) {
58         }
59         // When all tasks are running, half of tasks exit, quarter of tasks
60         // continue running and quarter of tasks schedule another 2 tasks each.
61         // Concurrently main thread schedules another quarter of tasks.
62         // This gives us another kThreads tasks and we ensure that they all
63         // are running.
64         if (i < kThreads / 2) {
65         } else if (i < 3 * kThreads / 4) {
66           running++;
67           while (phase < 3) {
68           }
69           done++;
70         } else {
71           for (int j = 0; j < 2; ++j) {
72             tp.Schedule([&]() {
73               running++;
74               while (phase < 3) {
75               }
76               done++;
77             });
78           }
79         }
80         done++;
81       });
82     }
83     while (running != kThreads) {
84     }
85     running = 0;
86     phase = 2;
87     for (int i = 0; i < kThreads / 4; ++i) {
88       tp.Schedule([&]() {
89         running++;
90         while (phase < 3) {
91         }
92         done++;
93       });
94     }
95     while (running != kThreads) {
96     }
97     phase = 3;
98     while (done != 3 * kThreads) {
99     }
100   }
101 }
102 
103 void test_cxx11_non_blocking_thread_pool()
104 {
105   CALL_SUBTEST(test_create_destroy_empty_pool());
106   CALL_SUBTEST(test_parallelism());
107 }
108