1/*
2 * Copyright (C) 2011 University of Szeged
3 * Copyright (C) 2011 Gabor Loki <loki@webkit.org>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY UNIVERSITY OF SZEGED ``AS IS'' AND ANY
16 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
18 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL UNIVERSITY OF SZEGED OR
19 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
20 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
22 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
23 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28#ifndef ParallelJobs_h
29#define ParallelJobs_h
30
31#include "platform/Task.h"
32#include "public/platform/Platform.h"
33#include "public/platform/WebThread.h"
34#include "wtf/Assertions.h"
35#include "wtf/Noncopyable.h"
36#include "wtf/OwnPtr.h"
37#include "wtf/Vector.h"
38
39// Usage:
40//
41//     // Initialize parallel jobs
42//     ParallelJobs<TypeOfParameter> parallelJobs(&worker, requestedNumberOfJobs);
43//
44//     // Fill the parameter array
45//     for(i = 0; i < parallelJobs.numberOfJobs(); ++i) {
46//       TypeOfParameter& params = parallelJobs.parameter(i);
47//       params.attr1 = localVars ...
48//       ...
49//     }
50//
51//     // Execute parallel jobs
52//     parallelJobs.execute();
53//
54
55namespace blink {
56
57template<typename Type>
58class ParallelJobs {
59    WTF_MAKE_NONCOPYABLE(ParallelJobs);
60    WTF_MAKE_FAST_ALLOCATED;
61public:
62    typedef void (*WorkerFunction)(Type*);
63
64    ParallelJobs(WorkerFunction func, size_t requestedJobNumber)
65        : m_func(func)
66    {
67        size_t numberOfJobs = std::max(static_cast<size_t>(2), std::min(requestedJobNumber, Platform::current()->numberOfProcessors()));
68        m_parameters.grow(numberOfJobs);
69        // The main thread can execute one job, so only create requestJobNumber - 1 threads.
70        for (size_t i = 0; i < numberOfJobs - 1; ++i) {
71            OwnPtr<WebThread> thread = adoptPtr(Platform::current()->createThread("Unfortunate parallel worker"));
72            m_threads.append(thread.release());
73        }
74    }
75
76    size_t numberOfJobs()
77    {
78        return m_parameters.size();
79    }
80
81    Type& parameter(size_t i)
82    {
83        return m_parameters[i];
84    }
85
86    void execute()
87    {
88        for (size_t i = 0; i < numberOfJobs() - 1; ++i)
89            m_threads[i]->postTask(new Task(WTF::bind(m_func, &parameter(i))));
90        m_func(&parameter(numberOfJobs() - 1));
91        m_threads.clear();
92    }
93
94private:
95    WorkerFunction m_func;
96    Vector<OwnPtr<WebThread> > m_threads;
97    Vector<Type> m_parameters;
98};
99
100} // namespace blink
101
102#endif // ParallelJobs_h
103