1 // Copyright (c) 2012 The Bitcoin developers
2 // Distributed under the MIT/X11 software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
11 #include <boost/foreach.hpp>
12 #include <boost/thread/condition_variable.hpp>
13 #include <boost/thread/locks.hpp>
14 #include <boost/thread/mutex.hpp>
16 extern bool fShutdown;
18 template<typename T> class CCheckQueueControl;
20 /** Queue for verifications that have to be performed.
21 * The verifications are represented by a type T, which must provide an
22 * operator(), returning a bool.
24 * One thread (the master) is assumed to push batches of verifications
25 * onto the queue, where they are processed by N-1 worker threads. When
26 * the master is done adding work, it temporarily joins the worker pool
27 * as an N'th worker, until all jobs are done.
29 template<typename T> class CCheckQueue {
31 // Mutex to protect the inner state
34 // Worker threads block on this when out of work
35 boost::condition_variable condWorker;
37 // Master thread blocks on this when out of work
38 boost::condition_variable condMaster;
40 // Quit method blocks on this until all workers are gone
41 boost::condition_variable condQuit;
43 // The queue of elements to be processed.
44 // As the order of booleans doesn't matter, it is used as a LIFO (stack)
47 // The number of workers (including the master) that are idle.
50 // The total number of workers (including the master).
53 // The temporary evaluation result.
56 // Number of verifications that haven't completed yet.
57 // This includes elements that are not anymore in queue, but still in
58 // worker's own batches.
61 // Whether we're shutting down.
64 // The maximum number of elements to be processed in one batch
65 unsigned int nBatchSize;
67 // Internal function that does bulk of the verification work.
68 bool Loop(bool fMaster = false) {
69 boost::condition_variable &cond = fMaster ? condMaster : condWorker;
70 std::vector<T> vChecks;
71 vChecks.reserve(nBatchSize);
72 unsigned int nNow = 0;
76 boost::unique_lock<boost::mutex> lock(mutex);
77 // first do the clean-up of the previous loop run (allowing us to do it in the same critsect)
81 if (nTodo == 0 && !fMaster)
82 // We processed the last element; inform the master he can exit and return the result
83 condMaster.notify_one();
88 // logically, the do loop starts here
89 while (queue.empty()) {
90 if ((fMaster || fQuit) && nTodo == 0) {
93 condQuit.notify_one();
95 // reset the status for new work later
98 // return the current status
102 cond.wait(lock); // wait
105 // Decide how many work units to process now.
106 // * Do not try to do everything at once, but aim for increasingly smaller batches so
107 // all workers finish approximately simultaneously.
108 // * Try to account for idle jobs which will instantly start helping.
109 // * Don't do batches smaller than 1 (duh), or larger than nBatchSize.
110 nNow = std::max(1U, std::min(nBatchSize, (unsigned int)queue.size() / (nTotal + nIdle + 1)));
111 vChecks.resize(nNow);
112 for (unsigned int i = 0; i < nNow; i++) {
113 // We want the lock on the mutex to be as short as possible, so swap jobs from the global
114 // queue to the local batch vector instead of copying.
115 vChecks[i].swap(queue.back());
118 // Check whether we need to do work at all
122 BOOST_FOREACH(T &check, vChecks)
126 } while(true && !fShutdown); // HACK: force queue to shut down
131 // Create a new check queue
132 CCheckQueue(unsigned int nBatchSizeIn) :
133 nIdle(0), nTotal(0), fAllOk(true), nTodo(0), fQuit(false), nBatchSize(nBatchSizeIn) {}
140 // Wait until execution finishes, and return whether all evaluations where succesful.
145 // Add a batch of checks to the queue
146 void Add(std::vector<T> &vChecks) {
147 boost::unique_lock<boost::mutex> lock(mutex);
148 BOOST_FOREACH(T &check, vChecks) {
149 queue.push_back(T());
150 check.swap(queue.back());
152 nTodo += vChecks.size();
153 if (vChecks.size() == 1)
154 condWorker.notify_one();
155 else if (vChecks.size() > 1)
156 condWorker.notify_all();
159 // Shut the queue down
161 boost::unique_lock<boost::mutex> lock(mutex);
163 // No need to wake the master, as he will quit automatically when all jobs are
165 condWorker.notify_all();
177 boost::unique_lock<boost::mutex> lock(mutex);
178 return (nTotal == nIdle && nTodo == 0 && fAllOk == true);
182 /** RAII-style controller object for a CCheckQueue that guarantees the passed
183 * queue is finished before continuing.
185 template<typename T> class CCheckQueueControl {
187 CCheckQueue<T> *pqueue;
191 CCheckQueueControl(CCheckQueue<T> *pqueueIn) : pqueue(pqueueIn), fDone(false) {
192 // passed queue is supposed to be unused, or NULL
193 if (pqueue != NULL) {
194 bool isIdle = pqueue->IsIdle();
202 bool fRet = pqueue->Wait();
207 void Add(std::vector<T> &vChecks) {
209 pqueue->Add(vChecks);
212 ~CCheckQueueControl() {