1 /*
2     Copyright (c) 2023 Intel Corporation
3 
4     Licensed under the Apache License, Version 2.0 (the "License");
5     you may not use this file except in compliance with the License.
6     You may obtain a copy of the License at
7 
8         http://www.apache.org/licenses/LICENSE-2.0
9 
10     Unless required by applicable law or agreed to in writing, software
11     distributed under the License is distributed on an "AS IS" BASIS,
12     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13     See the License for the specific language governing permissions and
14     limitations under the License.
15 */
16 
17 #ifndef TWO_TASKS_HEADER
18 #define TWO_TASKS_HEADER
19 
20 #include "task_emulation_layer.h"
21 
22 #include <iostream>
23 #include <numeric>
24 #include <utility>
25 #include <functional>
26 
27 extern int cutoff;
28 
29 long serial_fib(int n) {
30     return n < 2 ? n : serial_fib(n - 1) + serial_fib(n - 2);
31 }
32 
33 struct fib_continuation : task_emulation::base_task {
34     fib_continuation(int& s) : sum(s) {}
35 
36     void execute() override {
37         sum = x + y;
38     }
39 
40     int x{ 0 }, y{ 0 };
41     int& sum;
42 };
43 
44 struct fib_computation : task_emulation::base_task {
45     fib_computation(int n, int* x) : n(n), x(x) {}
46 
47     void execute() override {
48         if (n < cutoff) {
49             *x = serial_fib(n);
50         }
51         else {
52             // Continuation passing
53             auto& c = *this->allocate_continuation<fib_continuation>(/* children_counter = */ 2, *x);
54             task_emulation::run_task(c.create_child<fib_computation>(n - 1, &c.x));
55 
56             // Recycling
57             this->recycle_as_child_of(c);
58             n = n - 2;
59             x = &c.y;
60 
61             // Bypass is not supported by task_emulation and next_task executed directly.
62             // However, the old-TBB bypass behavior can be achieved with
63             // `return task_group::defer()` (check Migration Guide).
64             // Consider submit another task if recursion call is not acceptable
65             // i.e. instead of Recycling + Direct Body call
66             // submit task_emulation::run_task(c.create_child<fib_computation>(n - 2, &c.y));
67             this->operator()();
68         }
69     }
70 
71     int n;
72     int* x;
73 };
74 
75 int fibonacci_two_tasks(int n) {
76     int sum{};
77     tbb::task_group tg;
78     tg.run_and_wait(
79         task_emulation::create_root_task<fib_computation>(/* for root task = */ tg, n, &sum));
80     return sum;
81 }
82 
83 #endif // TWO_TASKS_HEADER
84