| 1 | n/a | # Defines classes that provide synchronization objects. Note that use of |
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| 2 | n/a | # this module requires that your Python support threads. |
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| 3 | n/a | # |
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| 4 | n/a | # condition(lock=None) # a POSIX-like condition-variable object |
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| 5 | n/a | # barrier(n) # an n-thread barrier |
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| 6 | n/a | # event() # an event object |
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| 7 | n/a | # semaphore(n=1) # a semaphore object, with initial count n |
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| 8 | n/a | # mrsw() # a multiple-reader single-writer lock |
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| 9 | n/a | # |
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| 10 | n/a | # CONDITIONS |
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| 11 | n/a | # |
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| 12 | n/a | # A condition object is created via |
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| 13 | n/a | # import this_module |
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| 14 | n/a | # your_condition_object = this_module.condition(lock=None) |
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| 15 | n/a | # |
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| 16 | n/a | # As explained below, a condition object has a lock associated with it, |
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| 17 | n/a | # used in the protocol to protect condition data. You can specify a |
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| 18 | n/a | # lock to use in the constructor, else the constructor will allocate |
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| 19 | n/a | # an anonymous lock for you. Specifying a lock explicitly can be useful |
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| 20 | n/a | # when more than one condition keys off the same set of shared data. |
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| 21 | n/a | # |
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| 22 | n/a | # Methods: |
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| 23 | n/a | # .acquire() |
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| 24 | n/a | # acquire the lock associated with the condition |
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| 25 | n/a | # .release() |
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| 26 | n/a | # release the lock associated with the condition |
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| 27 | n/a | # .wait() |
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| 28 | n/a | # block the thread until such time as some other thread does a |
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| 29 | n/a | # .signal or .broadcast on the same condition, and release the |
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| 30 | n/a | # lock associated with the condition. The lock associated with |
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| 31 | n/a | # the condition MUST be in the acquired state at the time |
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| 32 | n/a | # .wait is invoked. |
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| 33 | n/a | # .signal() |
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| 34 | n/a | # wake up exactly one thread (if any) that previously did a .wait |
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| 35 | n/a | # on the condition; that thread will awaken with the lock associated |
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| 36 | n/a | # with the condition in the acquired state. If no threads are |
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| 37 | n/a | # .wait'ing, this is a nop. If more than one thread is .wait'ing on |
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| 38 | n/a | # the condition, any of them may be awakened. |
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| 39 | n/a | # .broadcast() |
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| 40 | n/a | # wake up all threads (if any) that are .wait'ing on the condition; |
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| 41 | n/a | # the threads are woken up serially, each with the lock in the |
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| 42 | n/a | # acquired state, so should .release() as soon as possible. If no |
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| 43 | n/a | # threads are .wait'ing, this is a nop. |
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| 44 | n/a | # |
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| 45 | n/a | # Note that if a thread does a .wait *while* a signal/broadcast is |
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| 46 | n/a | # in progress, it's guaranteeed to block until a subsequent |
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| 47 | n/a | # signal/broadcast. |
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| 48 | n/a | # |
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| 49 | n/a | # Secret feature: `broadcast' actually takes an integer argument, |
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| 50 | n/a | # and will wake up exactly that many waiting threads (or the total |
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| 51 | n/a | # number waiting, if that's less). Use of this is dubious, though, |
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| 52 | n/a | # and probably won't be supported if this form of condition is |
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| 53 | n/a | # reimplemented in C. |
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| 54 | n/a | # |
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| 55 | n/a | # DIFFERENCES FROM POSIX |
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| 56 | n/a | # |
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| 57 | n/a | # + A separate mutex is not needed to guard condition data. Instead, a |
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| 58 | n/a | # condition object can (must) be .acquire'ed and .release'ed directly. |
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| 59 | n/a | # This eliminates a common error in using POSIX conditions. |
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| 60 | n/a | # |
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| 61 | n/a | # + Because of implementation difficulties, a POSIX `signal' wakes up |
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| 62 | n/a | # _at least_ one .wait'ing thread. Race conditions make it difficult |
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| 63 | n/a | # to stop that. This implementation guarantees to wake up only one, |
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| 64 | n/a | # but you probably shouldn't rely on that. |
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| 65 | n/a | # |
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| 66 | n/a | # PROTOCOL |
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| 67 | n/a | # |
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| 68 | n/a | # Condition objects are used to block threads until "some condition" is |
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| 69 | n/a | # true. E.g., a thread may wish to wait until a producer pumps out data |
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| 70 | n/a | # for it to consume, or a server may wish to wait until someone requests |
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| 71 | n/a | # its services, or perhaps a whole bunch of threads want to wait until a |
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| 72 | n/a | # preceding pass over the data is complete. Early models for conditions |
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| 73 | n/a | # relied on some other thread figuring out when a blocked thread's |
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| 74 | n/a | # condition was true, and made the other thread responsible both for |
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| 75 | n/a | # waking up the blocked thread and guaranteeing that it woke up with all |
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| 76 | n/a | # data in a correct state. This proved to be very delicate in practice, |
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| 77 | n/a | # and gave conditions a bad name in some circles. |
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| 78 | n/a | # |
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| 79 | n/a | # The POSIX model addresses these problems by making a thread responsible |
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| 80 | n/a | # for ensuring that its own state is correct when it wakes, and relies |
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| 81 | n/a | # on a rigid protocol to make this easy; so long as you stick to the |
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| 82 | n/a | # protocol, POSIX conditions are easy to "get right": |
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| 83 | n/a | # |
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| 84 | n/a | # A) The thread that's waiting for some arbitrarily-complex condition |
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| 85 | n/a | # (ACC) to become true does: |
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| 86 | n/a | # |
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| 87 | n/a | # condition.acquire() |
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| 88 | n/a | # while not (code to evaluate the ACC): |
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| 89 | n/a | # condition.wait() |
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| 90 | n/a | # # That blocks the thread, *and* releases the lock. When a |
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| 91 | n/a | # # condition.signal() happens, it will wake up some thread that |
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| 92 | n/a | # # did a .wait, *and* acquire the lock again before .wait |
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| 93 | n/a | # # returns. |
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| 94 | n/a | # # |
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| 95 | n/a | # # Because the lock is acquired at this point, the state used |
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| 96 | n/a | # # in evaluating the ACC is frozen, so it's safe to go back & |
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| 97 | n/a | # # reevaluate the ACC. |
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| 98 | n/a | # |
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| 99 | n/a | # # At this point, ACC is true, and the thread has the condition |
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| 100 | n/a | # # locked. |
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| 101 | n/a | # # So code here can safely muck with the shared state that |
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| 102 | n/a | # # went into evaluating the ACC -- if it wants to. |
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| 103 | n/a | # # When done mucking with the shared state, do |
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| 104 | n/a | # condition.release() |
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| 105 | n/a | # |
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| 106 | n/a | # B) Threads that are mucking with shared state that may affect the |
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| 107 | n/a | # ACC do: |
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| 108 | n/a | # |
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| 109 | n/a | # condition.acquire() |
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| 110 | n/a | # # muck with shared state |
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| 111 | n/a | # condition.release() |
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| 112 | n/a | # if it's possible that ACC is true now: |
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| 113 | n/a | # condition.signal() # or .broadcast() |
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| 114 | n/a | # |
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| 115 | n/a | # Note: You may prefer to put the "if" clause before the release(). |
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| 116 | n/a | # That's fine, but do note that anyone waiting on the signal will |
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| 117 | n/a | # stay blocked until the release() is done (since acquiring the |
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| 118 | n/a | # condition is part of what .wait() does before it returns). |
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| 119 | n/a | # |
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| 120 | n/a | # TRICK OF THE TRADE |
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| 121 | n/a | # |
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| 122 | n/a | # With simpler forms of conditions, it can be impossible to know when |
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| 123 | n/a | # a thread that's supposed to do a .wait has actually done it. But |
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| 124 | n/a | # because this form of condition releases a lock as _part_ of doing a |
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| 125 | n/a | # wait, the state of that lock can be used to guarantee it. |
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| 126 | n/a | # |
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| 127 | n/a | # E.g., suppose thread A spawns thread B and later wants to wait for B to |
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| 128 | n/a | # complete: |
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| 129 | n/a | # |
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| 130 | n/a | # In A: In B: |
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| 131 | n/a | # |
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| 132 | n/a | # B_done = condition() ... do work ... |
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| 133 | n/a | # B_done.acquire() B_done.acquire(); B_done.release() |
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| 134 | n/a | # spawn B B_done.signal() |
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| 135 | n/a | # ... some time later ... ... and B exits ... |
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| 136 | n/a | # B_done.wait() |
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| 137 | n/a | # |
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| 138 | n/a | # Because B_done was in the acquire'd state at the time B was spawned, |
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| 139 | n/a | # B's attempt to acquire B_done can't succeed until A has done its |
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| 140 | n/a | # B_done.wait() (which releases B_done). So B's B_done.signal() is |
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| 141 | n/a | # guaranteed to be seen by the .wait(). Without the lock trick, B |
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| 142 | n/a | # may signal before A .waits, and then A would wait forever. |
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| 143 | n/a | # |
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| 144 | n/a | # BARRIERS |
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| 145 | n/a | # |
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| 146 | n/a | # A barrier object is created via |
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| 147 | n/a | # import this_module |
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| 148 | n/a | # your_barrier = this_module.barrier(num_threads) |
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| 149 | n/a | # |
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| 150 | n/a | # Methods: |
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| 151 | n/a | # .enter() |
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| 152 | n/a | # the thread blocks until num_threads threads in all have done |
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| 153 | n/a | # .enter(). Then the num_threads threads that .enter'ed resume, |
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| 154 | n/a | # and the barrier resets to capture the next num_threads threads |
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| 155 | n/a | # that .enter it. |
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| 156 | n/a | # |
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| 157 | n/a | # EVENTS |
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| 158 | n/a | # |
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| 159 | n/a | # An event object is created via |
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| 160 | n/a | # import this_module |
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| 161 | n/a | # your_event = this_module.event() |
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| 162 | n/a | # |
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| 163 | n/a | # An event has two states, `posted' and `cleared'. An event is |
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| 164 | n/a | # created in the cleared state. |
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| 165 | n/a | # |
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| 166 | n/a | # Methods: |
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| 167 | n/a | # |
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| 168 | n/a | # .post() |
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| 169 | n/a | # Put the event in the posted state, and resume all threads |
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| 170 | n/a | # .wait'ing on the event (if any). |
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| 171 | n/a | # |
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| 172 | n/a | # .clear() |
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| 173 | n/a | # Put the event in the cleared state. |
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| 174 | n/a | # |
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| 175 | n/a | # .is_posted() |
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| 176 | n/a | # Returns 0 if the event is in the cleared state, or 1 if the event |
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| 177 | n/a | # is in the posted state. |
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| 178 | n/a | # |
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| 179 | n/a | # .wait() |
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| 180 | n/a | # If the event is in the posted state, returns immediately. |
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| 181 | n/a | # If the event is in the cleared state, blocks the calling thread |
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| 182 | n/a | # until the event is .post'ed by another thread. |
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| 183 | n/a | # |
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| 184 | n/a | # Note that an event, once posted, remains posted until explicitly |
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| 185 | n/a | # cleared. Relative to conditions, this is both the strength & weakness |
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| 186 | n/a | # of events. It's a strength because the .post'ing thread doesn't have to |
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| 187 | n/a | # worry about whether the threads it's trying to communicate with have |
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| 188 | n/a | # already done a .wait (a condition .signal is seen only by threads that |
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| 189 | n/a | # do a .wait _prior_ to the .signal; a .signal does not persist). But |
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| 190 | n/a | # it's a weakness because .clear'ing an event is error-prone: it's easy |
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| 191 | n/a | # to mistakenly .clear an event before all the threads you intended to |
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| 192 | n/a | # see the event get around to .wait'ing on it. But so long as you don't |
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| 193 | n/a | # need to .clear an event, events are easy to use safely. |
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| 194 | n/a | # |
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| 195 | n/a | # SEMAPHORES |
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| 196 | n/a | # |
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| 197 | n/a | # A semaphore object is created via |
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| 198 | n/a | # import this_module |
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| 199 | n/a | # your_semaphore = this_module.semaphore(count=1) |
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| 200 | n/a | # |
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| 201 | n/a | # A semaphore has an integer count associated with it. The initial value |
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| 202 | n/a | # of the count is specified by the optional argument (which defaults to |
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| 203 | n/a | # 1) passed to the semaphore constructor. |
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| 204 | n/a | # |
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| 205 | n/a | # Methods: |
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| 206 | n/a | # |
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| 207 | n/a | # .p() |
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| 208 | n/a | # If the semaphore's count is greater than 0, decrements the count |
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| 209 | n/a | # by 1 and returns. |
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| 210 | n/a | # Else if the semaphore's count is 0, blocks the calling thread |
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| 211 | n/a | # until a subsequent .v() increases the count. When that happens, |
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| 212 | n/a | # the count will be decremented by 1 and the calling thread resumed. |
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| 213 | n/a | # |
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| 214 | n/a | # .v() |
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| 215 | n/a | # Increments the semaphore's count by 1, and wakes up a thread (if |
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| 216 | n/a | # any) blocked by a .p(). It's an (detected) error for a .v() to |
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| 217 | n/a | # increase the semaphore's count to a value larger than the initial |
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| 218 | n/a | # count. |
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| 219 | n/a | # |
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| 220 | n/a | # MULTIPLE-READER SINGLE-WRITER LOCKS |
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| 221 | n/a | # |
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| 222 | n/a | # A mrsw lock is created via |
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| 223 | n/a | # import this_module |
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| 224 | n/a | # your_mrsw_lock = this_module.mrsw() |
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| 225 | n/a | # |
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| 226 | n/a | # This kind of lock is often useful with complex shared data structures. |
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| 227 | n/a | # The object lets any number of "readers" proceed, so long as no thread |
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| 228 | n/a | # wishes to "write". When a (one or more) thread declares its intention |
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| 229 | n/a | # to "write" (e.g., to update a shared structure), all current readers |
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| 230 | n/a | # are allowed to finish, and then a writer gets exclusive access; all |
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| 231 | n/a | # other readers & writers are blocked until the current writer completes. |
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| 232 | n/a | # Finally, if some thread is waiting to write and another is waiting to |
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| 233 | n/a | # read, the writer takes precedence. |
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| 234 | n/a | # |
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| 235 | n/a | # Methods: |
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| 236 | n/a | # |
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| 237 | n/a | # .read_in() |
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| 238 | n/a | # If no thread is writing or waiting to write, returns immediately. |
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| 239 | n/a | # Else blocks until no thread is writing or waiting to write. So |
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| 240 | n/a | # long as some thread has completed a .read_in but not a .read_out, |
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| 241 | n/a | # writers are blocked. |
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| 242 | n/a | # |
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| 243 | n/a | # .read_out() |
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| 244 | n/a | # Use sometime after a .read_in to declare that the thread is done |
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| 245 | n/a | # reading. When all threads complete reading, a writer can proceed. |
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| 246 | n/a | # |
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| 247 | n/a | # .write_in() |
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| 248 | n/a | # If no thread is writing (has completed a .write_in, but hasn't yet |
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| 249 | n/a | # done a .write_out) or reading (similarly), returns immediately. |
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| 250 | n/a | # Else blocks the calling thread, and threads waiting to read, until |
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| 251 | n/a | # the current writer completes writing or all the current readers |
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| 252 | n/a | # complete reading; if then more than one thread is waiting to |
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| 253 | n/a | # write, one of them is allowed to proceed, but which one is not |
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| 254 | n/a | # specified. |
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| 255 | n/a | # |
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| 256 | n/a | # .write_out() |
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| 257 | n/a | # Use sometime after a .write_in to declare that the thread is done |
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| 258 | n/a | # writing. Then if some other thread is waiting to write, it's |
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| 259 | n/a | # allowed to proceed. Else all threads (if any) waiting to read are |
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| 260 | n/a | # allowed to proceed. |
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| 261 | n/a | # |
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| 262 | n/a | # .write_to_read() |
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| 263 | n/a | # Use instead of a .write_in to declare that the thread is done |
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| 264 | n/a | # writing but wants to continue reading without other writers |
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| 265 | n/a | # intervening. If there are other threads waiting to write, they |
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| 266 | n/a | # are allowed to proceed only if the current thread calls |
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| 267 | n/a | # .read_out; threads waiting to read are only allowed to proceed |
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| 268 | n/a | # if there are are no threads waiting to write. (This is a |
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| 269 | n/a | # weakness of the interface!) |
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| 270 | n/a | |
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| 271 | n/a | import _thread as thread |
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| 272 | n/a | |
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| 273 | n/a | class condition: |
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| 274 | n/a | def __init__(self, lock=None): |
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| 275 | n/a | # the lock actually used by .acquire() and .release() |
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| 276 | n/a | if lock is None: |
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| 277 | n/a | self.mutex = thread.allocate_lock() |
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| 278 | n/a | else: |
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| 279 | n/a | if hasattr(lock, 'acquire') and \ |
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| 280 | n/a | hasattr(lock, 'release'): |
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| 281 | n/a | self.mutex = lock |
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| 282 | n/a | else: |
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| 283 | n/a | raise TypeError('condition constructor requires ' \ |
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| 284 | n/a | 'a lock argument') |
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| 285 | n/a | |
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| 286 | n/a | # lock used to block threads until a signal |
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| 287 | n/a | self.checkout = thread.allocate_lock() |
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| 288 | n/a | self.checkout.acquire() |
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| 289 | n/a | |
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| 290 | n/a | # internal critical-section lock, & the data it protects |
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| 291 | n/a | self.idlock = thread.allocate_lock() |
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| 292 | n/a | self.id = 0 |
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| 293 | n/a | self.waiting = 0 # num waiters subject to current release |
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| 294 | n/a | self.pending = 0 # num waiters awaiting next signal |
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| 295 | n/a | self.torelease = 0 # num waiters to release |
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| 296 | n/a | self.releasing = 0 # 1 iff release is in progress |
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| 297 | n/a | |
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| 298 | n/a | def acquire(self): |
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| 299 | n/a | self.mutex.acquire() |
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| 300 | n/a | |
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| 301 | n/a | def release(self): |
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| 302 | n/a | self.mutex.release() |
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| 303 | n/a | |
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| 304 | n/a | def wait(self): |
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| 305 | n/a | mutex, checkout, idlock = self.mutex, self.checkout, self.idlock |
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| 306 | n/a | if not mutex.locked(): |
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| 307 | n/a | raise ValueError("condition must be .acquire'd when .wait() invoked") |
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| 308 | n/a | |
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| 309 | n/a | idlock.acquire() |
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| 310 | n/a | myid = self.id |
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| 311 | n/a | self.pending = self.pending + 1 |
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| 312 | n/a | idlock.release() |
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| 313 | n/a | |
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| 314 | n/a | mutex.release() |
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| 315 | n/a | |
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| 316 | n/a | while 1: |
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| 317 | n/a | checkout.acquire(); idlock.acquire() |
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| 318 | n/a | if myid < self.id: |
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| 319 | n/a | break |
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| 320 | n/a | checkout.release(); idlock.release() |
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| 321 | n/a | |
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| 322 | n/a | self.waiting = self.waiting - 1 |
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| 323 | n/a | self.torelease = self.torelease - 1 |
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| 324 | n/a | if self.torelease: |
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| 325 | n/a | checkout.release() |
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| 326 | n/a | else: |
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| 327 | n/a | self.releasing = 0 |
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| 328 | n/a | if self.waiting == self.pending == 0: |
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| 329 | n/a | self.id = 0 |
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| 330 | n/a | idlock.release() |
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| 331 | n/a | mutex.acquire() |
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| 332 | n/a | |
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| 333 | n/a | def signal(self): |
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| 334 | n/a | self.broadcast(1) |
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| 335 | n/a | |
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| 336 | n/a | def broadcast(self, num = -1): |
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| 337 | n/a | if num < -1: |
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| 338 | n/a | raise ValueError('.broadcast called with num %r' % (num,)) |
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| 339 | n/a | if num == 0: |
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| 340 | n/a | return |
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| 341 | n/a | self.idlock.acquire() |
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| 342 | n/a | if self.pending: |
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| 343 | n/a | self.waiting = self.waiting + self.pending |
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| 344 | n/a | self.pending = 0 |
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| 345 | n/a | self.id = self.id + 1 |
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| 346 | n/a | if num == -1: |
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| 347 | n/a | self.torelease = self.waiting |
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| 348 | n/a | else: |
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| 349 | n/a | self.torelease = min( self.waiting, |
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| 350 | n/a | self.torelease + num ) |
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| 351 | n/a | if self.torelease and not self.releasing: |
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| 352 | n/a | self.releasing = 1 |
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| 353 | n/a | self.checkout.release() |
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| 354 | n/a | self.idlock.release() |
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| 355 | n/a | |
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| 356 | n/a | class barrier: |
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| 357 | n/a | def __init__(self, n): |
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| 358 | n/a | self.n = n |
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| 359 | n/a | self.togo = n |
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| 360 | n/a | self.full = condition() |
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| 361 | n/a | |
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| 362 | n/a | def enter(self): |
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| 363 | n/a | full = self.full |
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| 364 | n/a | full.acquire() |
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| 365 | n/a | self.togo = self.togo - 1 |
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| 366 | n/a | if self.togo: |
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| 367 | n/a | full.wait() |
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| 368 | n/a | else: |
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| 369 | n/a | self.togo = self.n |
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| 370 | n/a | full.broadcast() |
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| 371 | n/a | full.release() |
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| 372 | n/a | |
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| 373 | n/a | class event: |
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| 374 | n/a | def __init__(self): |
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| 375 | n/a | self.state = 0 |
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| 376 | n/a | self.posted = condition() |
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| 377 | n/a | |
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| 378 | n/a | def post(self): |
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| 379 | n/a | self.posted.acquire() |
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| 380 | n/a | self.state = 1 |
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| 381 | n/a | self.posted.broadcast() |
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| 382 | n/a | self.posted.release() |
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| 383 | n/a | |
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| 384 | n/a | def clear(self): |
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| 385 | n/a | self.posted.acquire() |
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| 386 | n/a | self.state = 0 |
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| 387 | n/a | self.posted.release() |
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| 388 | n/a | |
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| 389 | n/a | def is_posted(self): |
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| 390 | n/a | self.posted.acquire() |
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| 391 | n/a | answer = self.state |
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| 392 | n/a | self.posted.release() |
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| 393 | n/a | return answer |
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| 394 | n/a | |
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| 395 | n/a | def wait(self): |
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| 396 | n/a | self.posted.acquire() |
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| 397 | n/a | if not self.state: |
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| 398 | n/a | self.posted.wait() |
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| 399 | n/a | self.posted.release() |
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| 400 | n/a | |
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| 401 | n/a | class semaphore: |
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| 402 | n/a | def __init__(self, count=1): |
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| 403 | n/a | if count <= 0: |
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| 404 | n/a | raise ValueError('semaphore count %d; must be >= 1' % count) |
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| 405 | n/a | self.count = count |
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| 406 | n/a | self.maxcount = count |
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| 407 | n/a | self.nonzero = condition() |
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| 408 | n/a | |
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| 409 | n/a | def p(self): |
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| 410 | n/a | self.nonzero.acquire() |
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| 411 | n/a | while self.count == 0: |
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| 412 | n/a | self.nonzero.wait() |
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| 413 | n/a | self.count = self.count - 1 |
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| 414 | n/a | self.nonzero.release() |
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| 415 | n/a | |
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| 416 | n/a | def v(self): |
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| 417 | n/a | self.nonzero.acquire() |
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| 418 | n/a | if self.count == self.maxcount: |
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| 419 | n/a | raise ValueError('.v() tried to raise semaphore count above ' \ |
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| 420 | n/a | 'initial value %r' % self.maxcount) |
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| 421 | n/a | self.count = self.count + 1 |
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| 422 | n/a | self.nonzero.signal() |
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| 423 | n/a | self.nonzero.release() |
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| 424 | n/a | |
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| 425 | n/a | class mrsw: |
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| 426 | n/a | def __init__(self): |
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| 427 | n/a | # critical-section lock & the data it protects |
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| 428 | n/a | self.rwOK = thread.allocate_lock() |
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| 429 | n/a | self.nr = 0 # number readers actively reading (not just waiting) |
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| 430 | n/a | self.nw = 0 # number writers either waiting to write or writing |
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| 431 | n/a | self.writing = 0 # 1 iff some thread is writing |
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| 432 | n/a | |
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| 433 | n/a | # conditions |
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| 434 | n/a | self.readOK = condition(self.rwOK) # OK to unblock readers |
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| 435 | n/a | self.writeOK = condition(self.rwOK) # OK to unblock writers |
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| 436 | n/a | |
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| 437 | n/a | def read_in(self): |
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| 438 | n/a | self.rwOK.acquire() |
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| 439 | n/a | while self.nw: |
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| 440 | n/a | self.readOK.wait() |
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| 441 | n/a | self.nr = self.nr + 1 |
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| 442 | n/a | self.rwOK.release() |
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| 443 | n/a | |
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| 444 | n/a | def read_out(self): |
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| 445 | n/a | self.rwOK.acquire() |
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| 446 | n/a | if self.nr <= 0: |
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| 447 | n/a | raise ValueError('.read_out() invoked without an active reader') |
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| 448 | n/a | self.nr = self.nr - 1 |
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| 449 | n/a | if self.nr == 0: |
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| 450 | n/a | self.writeOK.signal() |
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| 451 | n/a | self.rwOK.release() |
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| 452 | n/a | |
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| 453 | n/a | def write_in(self): |
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| 454 | n/a | self.rwOK.acquire() |
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| 455 | n/a | self.nw = self.nw + 1 |
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| 456 | n/a | while self.writing or self.nr: |
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| 457 | n/a | self.writeOK.wait() |
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| 458 | n/a | self.writing = 1 |
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| 459 | n/a | self.rwOK.release() |
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| 460 | n/a | |
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| 461 | n/a | def write_out(self): |
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| 462 | n/a | self.rwOK.acquire() |
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| 463 | n/a | if not self.writing: |
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| 464 | n/a | raise ValueError('.write_out() invoked without an active writer') |
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| 465 | n/a | self.writing = 0 |
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| 466 | n/a | self.nw = self.nw - 1 |
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| 467 | n/a | if self.nw: |
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| 468 | n/a | self.writeOK.signal() |
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| 469 | n/a | else: |
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| 470 | n/a | self.readOK.broadcast() |
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| 471 | n/a | self.rwOK.release() |
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| 472 | n/a | |
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| 473 | n/a | def write_to_read(self): |
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| 474 | n/a | self.rwOK.acquire() |
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| 475 | n/a | if not self.writing: |
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| 476 | n/a | raise ValueError('.write_to_read() invoked without an active writer') |
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| 477 | n/a | self.writing = 0 |
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| 478 | n/a | self.nw = self.nw - 1 |
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| 479 | n/a | self.nr = self.nr + 1 |
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| 480 | n/a | if not self.nw: |
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| 481 | n/a | self.readOK.broadcast() |
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| 482 | n/a | self.rwOK.release() |
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| 483 | n/a | |
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| 484 | n/a | # The rest of the file is a test case, that runs a number of parallelized |
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| 485 | n/a | # quicksorts in parallel. If it works, you'll get about 600 lines of |
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| 486 | n/a | # tracing output, with a line like |
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| 487 | n/a | # test passed! 209 threads created in all |
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| 488 | n/a | # as the last line. The content and order of preceding lines will |
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| 489 | n/a | # vary across runs. |
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| 490 | n/a | |
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| 491 | n/a | def _new_thread(func, *args): |
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| 492 | n/a | global TID |
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| 493 | n/a | tid.acquire(); id = TID = TID+1; tid.release() |
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| 494 | n/a | io.acquire(); alive.append(id); \ |
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| 495 | n/a | print('starting thread', id, '--', len(alive), 'alive'); \ |
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| 496 | n/a | io.release() |
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| 497 | n/a | thread.start_new_thread( func, (id,) + args ) |
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| 498 | n/a | |
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| 499 | n/a | def _qsort(tid, a, l, r, finished): |
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| 500 | n/a | # sort a[l:r]; post finished when done |
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| 501 | n/a | io.acquire(); print('thread', tid, 'qsort', l, r); io.release() |
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| 502 | n/a | if r-l > 1: |
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| 503 | n/a | pivot = a[l] |
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| 504 | n/a | j = l+1 # make a[l:j] <= pivot, and a[j:r] > pivot |
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| 505 | n/a | for i in range(j, r): |
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| 506 | n/a | if a[i] <= pivot: |
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| 507 | n/a | a[j], a[i] = a[i], a[j] |
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| 508 | n/a | j = j + 1 |
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| 509 | n/a | a[l], a[j-1] = a[j-1], pivot |
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| 510 | n/a | |
|---|
| 511 | n/a | l_subarray_sorted = event() |
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| 512 | n/a | r_subarray_sorted = event() |
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| 513 | n/a | _new_thread(_qsort, a, l, j-1, l_subarray_sorted) |
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| 514 | n/a | _new_thread(_qsort, a, j, r, r_subarray_sorted) |
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| 515 | n/a | l_subarray_sorted.wait() |
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| 516 | n/a | r_subarray_sorted.wait() |
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| 517 | n/a | |
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| 518 | n/a | io.acquire(); print('thread', tid, 'qsort done'); \ |
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| 519 | n/a | alive.remove(tid); io.release() |
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| 520 | n/a | finished.post() |
|---|
| 521 | n/a | |
|---|
| 522 | n/a | def _randarray(tid, a, finished): |
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| 523 | n/a | io.acquire(); print('thread', tid, 'randomizing array'); \ |
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| 524 | n/a | io.release() |
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| 525 | n/a | for i in range(1, len(a)): |
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| 526 | n/a | wh.acquire(); j = randint(0,i); wh.release() |
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| 527 | n/a | a[i], a[j] = a[j], a[i] |
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| 528 | n/a | io.acquire(); print('thread', tid, 'randomizing done'); \ |
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| 529 | n/a | alive.remove(tid); io.release() |
|---|
| 530 | n/a | finished.post() |
|---|
| 531 | n/a | |
|---|
| 532 | n/a | def _check_sort(a): |
|---|
| 533 | n/a | if a != range(len(a)): |
|---|
| 534 | n/a | raise ValueError('a not sorted', a) |
|---|
| 535 | n/a | |
|---|
| 536 | n/a | def _run_one_sort(tid, a, bar, done): |
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| 537 | n/a | # randomize a, and quicksort it |
|---|
| 538 | n/a | # for variety, all the threads running this enter a barrier |
|---|
| 539 | n/a | # at the end, and post `done' after the barrier exits |
|---|
| 540 | n/a | io.acquire(); print('thread', tid, 'randomizing', a); \ |
|---|
| 541 | n/a | io.release() |
|---|
| 542 | n/a | finished = event() |
|---|
| 543 | n/a | _new_thread(_randarray, a, finished) |
|---|
| 544 | n/a | finished.wait() |
|---|
| 545 | n/a | |
|---|
| 546 | n/a | io.acquire(); print('thread', tid, 'sorting', a); io.release() |
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| 547 | n/a | finished.clear() |
|---|
| 548 | n/a | _new_thread(_qsort, a, 0, len(a), finished) |
|---|
| 549 | n/a | finished.wait() |
|---|
| 550 | n/a | _check_sort(a) |
|---|
| 551 | n/a | |
|---|
| 552 | n/a | io.acquire(); print('thread', tid, 'entering barrier'); \ |
|---|
| 553 | n/a | io.release() |
|---|
| 554 | n/a | bar.enter() |
|---|
| 555 | n/a | io.acquire(); print('thread', tid, 'leaving barrier'); \ |
|---|
| 556 | n/a | io.release() |
|---|
| 557 | n/a | io.acquire(); alive.remove(tid); io.release() |
|---|
| 558 | n/a | bar.enter() # make sure they've all removed themselves from alive |
|---|
| 559 | n/a | ## before 'done' is posted |
|---|
| 560 | n/a | bar.enter() # just to be cruel |
|---|
| 561 | n/a | done.post() |
|---|
| 562 | n/a | |
|---|
| 563 | n/a | def test(): |
|---|
| 564 | n/a | global TID, tid, io, wh, randint, alive |
|---|
| 565 | n/a | import random |
|---|
| 566 | n/a | randint = random.randint |
|---|
| 567 | n/a | |
|---|
| 568 | n/a | TID = 0 # thread ID (1, 2, ...) |
|---|
| 569 | n/a | tid = thread.allocate_lock() # for changing TID |
|---|
| 570 | n/a | io = thread.allocate_lock() # for printing, and 'alive' |
|---|
| 571 | n/a | wh = thread.allocate_lock() # for calls to random |
|---|
| 572 | n/a | alive = [] # IDs of active threads |
|---|
| 573 | n/a | |
|---|
| 574 | n/a | NSORTS = 5 |
|---|
| 575 | n/a | arrays = [] |
|---|
| 576 | n/a | for i in range(NSORTS): |
|---|
| 577 | n/a | arrays.append( range( (i+1)*10 ) ) |
|---|
| 578 | n/a | |
|---|
| 579 | n/a | bar = barrier(NSORTS) |
|---|
| 580 | n/a | finished = event() |
|---|
| 581 | n/a | for i in range(NSORTS): |
|---|
| 582 | n/a | _new_thread(_run_one_sort, arrays[i], bar, finished) |
|---|
| 583 | n/a | finished.wait() |
|---|
| 584 | n/a | |
|---|
| 585 | n/a | print('all threads done, and checking results ...') |
|---|
| 586 | n/a | if alive: |
|---|
| 587 | n/a | raise ValueError('threads still alive at end', alive) |
|---|
| 588 | n/a | for i in range(NSORTS): |
|---|
| 589 | n/a | a = arrays[i] |
|---|
| 590 | n/a | if len(a) != (i+1)*10: |
|---|
| 591 | n/a | raise ValueError('length of array', i, 'screwed up') |
|---|
| 592 | n/a | _check_sort(a) |
|---|
| 593 | n/a | |
|---|
| 594 | n/a | print('test passed!', TID, 'threads created in all') |
|---|
| 595 | n/a | |
|---|
| 596 | n/a | if __name__ == '__main__': |
|---|
| 597 | n/a | test() |
|---|
| 598 | n/a | |
|---|
| 599 | n/a | # end of module |
|---|
