Removed condition.py -- it was just sync.py without

the mrsw lock and without 'condition' allocating a lock by default

2 files changed, 0 insertions, 476 deletions

diff --git a/Demo/threads/README b/Demo/threads/README
index 91af273..c6c4a0b 100644
--- a/Demo/threads/README
+++ b/Demo/threads/README
@@ -4,7 +4,6 @@ These are mostly "proof of concept" type applications:
 
 Generator.py	Generator class implemented with threads.
 bug.py		Demonstrate a bug with importing modules in threads.
-condition.py	Appears to be an earlier version of sync.py.
 find.py		Parallelized "find(1)" (looks for directories).
 sync.py		Condition variables primitives by Tim Peters.
 telnet.py	Version of ../sockets/telnet.py using threads.
diff --git a/Demo/threads/condition.py b/Demo/threads/condition.py
deleted file mode 100755
index 4e99979..0000000
--- a/Demo/threads/condition.py
+++ /dev/null
@@ -1,475 +0,0 @@
-# Defines classes that provide synchronization objects.  Note that use of
-# this module requires that your Python support threads.
-#
-#    condition()   # a POSIX-like condition-variable object
-#    barrier(n)    # an n-thread barrier
-#    event()       # an event object
-#    semaphore(n=1)# a semaphore object, with initial count n
-#
-# CONDITIONS
-#
-# A condition object is created via
-#   import this_module
-#   your_condition_object = this_module.condition()
-#
-# Methods:
-#   .acquire()
-#      acquire the lock associated with the condition
-#   .release()
-#      release the lock associated with the condition
-#   .wait()
-#      block the thread until such time as some other thread does a
-#      .signal or .broadcast on the same condition, and release the
-#      lock associated with the condition.  The lock associated with
-#      the condition MUST be in the acquired state at the time
-#      .wait is invoked.
-#   .signal()
-#      wake up exactly one thread (if any) that previously did a .wait
-#      on the condition; that thread will awaken with the lock associated
-#      with the condition in the acquired state.  If no threads are
-#      .wait'ing, this is a nop.  If more than one thread is .wait'ing on
-#      the condition, any of them may be awakened.
-#   .broadcast()
-#      wake up all threads (if any) that are .wait'ing on the condition;
-#      the threads are woken up serially, each with the lock in the
-#      acquired state, so should .release() as soon as possible.  If no
-#      threads are .wait'ing, this is a nop.
-#
-#      Note that if a thread does a .wait *while* a signal/broadcast is
-#      in progress, it's guaranteeed to block until a subsequent
-#      signal/broadcast.
-#
-#      Secret feature:  `broadcast' actually takes an integer argument,
-#      and will wake up exactly that many waiting threads (or the total
-#      number waiting, if that's less).  Use of this is dubious, though,
-#      and probably won't be supported if this form of condition is
-#      reimplemented in C.
-#
-# DIFFERENCES FROM POSIX
-#
-# + A separate mutex is not needed to guard condition data.  Instead, a
-#   condition object can (must) be .acquire'ed and .release'ed directly.
-#   This eliminates a common error in using POSIX conditions.
-#
-# + Because of implementation difficulties, a POSIX `signal' wakes up
-#   _at least_ one .wait'ing thread.  Race conditions make it difficult
-#   to stop that.  This implementation guarantees to wake up only one,
-#   but you probably shouldn't rely on that.
-#
-# PROTOCOL
-#
-# Condition objects are used to block threads until "some condition" is
-# true.  E.g., a thread may wish to wait until a producer pumps out data
-# for it to consume, or a server may wish to wait until someone requests
-# its services, or perhaps a whole bunch of threads want to wait until a
-# preceding pass over the data is complete.  Early models for conditions
-# relied on some other thread figuring out when a blocked thread's
-# condition was true, and made the other thread responsible both for
-# waking up the blocked thread and guaranteeing that it woke up with all
-# data in a correct state.  This proved to be very delicate in practice,
-# and gave conditions a bad name in some circles.
-#
-# The POSIX model addresses these problems by making a thread responsible
-# for ensuring that its own state is correct when it wakes, and relies
-# on a rigid protocol to make this easy; so long as you stick to the
-# protocol, POSIX conditions are easy to "get right":
-#
-#  A) The thread that's waiting for some arbitrarily-complex condition
-#     (ACC) to become true does:
-#
-#     condition.acquire()
-#     while not (code to evaluate the ACC):
-#           condition.wait()
-#           # That blocks the thread, *and* releases the lock.  When a
-#           # condition.signal() happens, it will wake up some thread that
-#           # did a .wait, *and* acquire the lock again before .wait
-#           # returns.
-#           #
-#           # Because the lock is acquired at this point, the state used
-#           # in evaluating the ACC is frozen, so it's safe to go back &
-#           # reevaluate the ACC.
-#
-#     # At this point, ACC is true, and the thread has the condition
-#     # locked.
-#     # So code here can safely muck with the shared state that
-#     # went into evaluating the ACC -- if it wants to.
-#     # When done mucking with the shared state, do
-#     condition.release()
-#
-#  B) Threads that are mucking with shared state that may affect the
-#     ACC do:
-#
-#     condition.acquire()
-#     # muck with shared state
-#     condition.release()
-#     if it's possible that ACC is true now:
-#         condition.signal() # or .broadcast()
-#
-#     Note:  You may prefer to put the "if" clause before the release().
-#     That's fine, but do note that anyone waiting on the signal will
-#     stay blocked until the release() is done (since acquiring the
-#     condition is part of what .wait() does before it returns).
-#
-# TRICK OF THE TRADE
-#
-# With simpler forms of conditions, it can be impossible to know when
-# a thread that's supposed to do a .wait has actually done it.  But
-# because this form of condition releases a lock as _part_ of doing a
-# wait, the state of that lock can be used to guarantee it.
-#
-# E.g., suppose thread A spawns thread B and later wants to wait for B to
-# complete:
-#
-# In A:                             In B:
-#
-# B_done = condition()              ... do work ...
-# B_done.acquire()                  B_done.acquire(); B_done.release()
-# spawn B                           B_done.signal()
-# ... some time later ...           ... and B exits ...
-# B_done.wait()
-#
-# Because B_done was in the acquire'd state at the time B was spawned,
-# B's attempt to acquire B_done can't succeed until A has done its
-# B_done.wait() (which releases B_done).  So B's B_done.signal() is
-# guaranteed to be seen by the .wait().  Without the lock trick, B
-# may signal before A .waits, and then A would wait forever.
-#
-# BARRIERS
-#
-# A barrier object is created via
-#   import this_module
-#   your_barrier = this_module.barrier(num_threads)
-#
-# Methods:
-#   .enter()
-#      the thread blocks until num_threads threads in all have done
-#      .enter().  Then the num_threads threads that .enter'ed resume,
-#      and the barrier resets to capture the next num_threads threads
-#      that .enter it.
-#
-# EVENTS
-#
-# An event object is created via
-#   import this_module
-#   your_event = this_module.event()
-#
-# An event has two states, `posted' and `cleared'.  An event is
-# created in the cleared state.
-#
-# Methods:
-#
-#   .post()
-#      Put the event in the posted state, and resume all threads
-#      .wait'ing on the event (if any).
-#
-#   .clear()
-#      Put the event in the cleared state.
-#
-#   .is_posted()
-#      Returns 0 if the event is in the cleared state, or 1 if the event
-#      is in the posted state.
-#
-#   .wait()
-#      If the event is in the posted state, returns immediately.
-#      If the event is in the cleared state, blocks the calling thread
-#      until the event is .post'ed by another thread.
-#
-# Note that an event, once posted, remains posted until explicitly
-# cleared.  Relative to conditions, this is both the strength & weakness
-# of events.  It's a strength because the .post'ing thread doesn't have to
-# worry about whether the threads it's trying to communicate with have
-# already done a .wait (a condition .signal is seen only by threads that
-# do a .wait _prior_ to the .signal; a .signal does not persist).  But
-# it's a weakness because .clear'ing an event is error-prone:  it's easy
-# to mistakenly .clear an event before all the threads you intended to
-# see the event get around to .wait'ing on it.  But so long as you don't
-# need to .clear an event, events are easy to use safely.
-#
-# SEMAPHORES
-#
-# A semaphore object is created via
-#   import this_module
-#   your_semaphore = this_module.semaphore(count=1)
-#
-# A semaphore has an integer count associated with it.  The initial value
-# of the count is specified by the optional argument (which defaults to
-# 1) passed to the semaphore constructor.
-#
-# Methods:
-#
-#   .p()
-#      If the semaphore's count is greater than 0, decrements the count
-#      by 1 and returns.
-#      Else if the semaphore's count is 0, blocks the calling thread
-#      until a subsequent .v() increases the count.  When that happens,
-#      the count will be decremented by 1 and the calling thread resumed.
-#
-#   .v()
-#      Increments the semaphore's count by 1, and wakes up a thread (if
-#      any) blocked by a .p().  It's an (detected) error for a .v() to
-#      increase the semaphore's count to a value larger than the initial
-#      count.
-
-import thread
-
-class condition:
-    def __init__(self):
-        # the lock actually used by .acquire() and .release()
-        self.mutex = thread.allocate_lock()
-
-        # lock used to block threads until a signal
-        self.checkout = thread.allocate_lock()
-        self.checkout.acquire()
-
-        # internal critical-section lock, & the data it protects
-        self.idlock = thread.allocate_lock()
-        self.id = 0
-        self.waiting = 0  # num waiters subject to current release
-        self.pending = 0  # num waiters awaiting next signal
-        self.torelease = 0      # num waiters to release
-        self.releasing = 0      # 1 iff release is in progress
-
-    def acquire(self):
-        self.mutex.acquire()
-
-    def release(self):
-        self.mutex.release()
-
-    def wait(self):
-        mutex, checkout, idlock = self.mutex, self.checkout, self.idlock
-        if not mutex.locked():
-            raise ValueError, \
-                  "condition must be .acquire'd when .wait() invoked"
-
-        idlock.acquire()
-        myid = self.id
-        self.pending = self.pending + 1
-        idlock.release()
-
-        mutex.release()
-
-        while 1:
-            checkout.acquire(); idlock.acquire()
-            if myid < self.id:
-                break
-            checkout.release(); idlock.release()
-
-        self.waiting = self.waiting - 1
-        self.torelease = self.torelease - 1
-        if self.torelease:
-            checkout.release()
-        else:
-            self.releasing = 0
-            if self.waiting == self.pending == 0:
-                self.id = 0
-        idlock.release()
-        mutex.acquire()
-
-    def signal(self):
-        self.broadcast(1)
-
-    def broadcast(self, num = -1):
-        if num < -1:
-            raise ValueError, '.broadcast called with num ' + `num`
-        if num == 0:
-            return
-        self.idlock.acquire()
-        if self.pending:
-            self.waiting = self.waiting + self.pending
-            self.pending = 0
-            self.id = self.id + 1
-        if num == -1:
-            self.torelease = self.waiting
-        else:
-            self.torelease = min( self.waiting,
-                                  self.torelease + num )
-        if self.torelease and not self.releasing:
-            self.releasing = 1
-            self.checkout.release()
-        self.idlock.release()
-
-class barrier:
-    def __init__(self, n):
-        self.n = n
-        self.togo = n
-        self.full = condition()
-
-    def enter(self):
-        full = self.full
-        full.acquire()
-        self.togo = self.togo - 1
-        if self.togo:
-            full.wait()
-        else:
-            self.togo = self.n
-            full.broadcast()
-        full.release()
-
-class event:
-    def __init__(self):
-        self.state  = 0
-        self.posted = condition()
-
-    def post(self):
-        self.posted.acquire()
-        self.state = 1
-        self.posted.broadcast()
-        self.posted.release()
-
-    def clear(self):
-        self.posted.acquire()
-        self.state = 0
-        self.posted.release()
-
-    def is_posted(self):
-        self.posted.acquire()
-        answer = self.state
-        self.posted.release()
-        return answer
-
-    def wait(self):
-        self.posted.acquire()
-        if not self.state:
-            self.posted.wait()
-        self.posted.release()
-
-class semaphore:
-    def __init__(self, count=1):
-        if count <= 0:
-            raise ValueError, 'semaphore count %d; must be >= 1' % count
-        self.count = count
-        self.maxcount = count
-        self.nonzero = condition()
-
-    def p(self):
-        self.nonzero.acquire()
-        while self.count == 0:
-            self.nonzero.wait()
-        self.count = self.count - 1
-        self.nonzero.release()
-
-    def v(self):
-        self.nonzero.acquire()
-        if self.count == self.maxcount:
-            raise ValueError, '.v() tried to raise semaphore count above ' \
-                  'initial value ' + `maxcount`
-        self.count = self.count + 1
-        self.nonzero.signal()
-        self.nonzero.release()
-
-# The rest of the file is a test case, that runs a number of parallelized
-# quicksorts in parallel.  If it works, you'll get about 600 lines of
-# tracing output, with a line like
-#     test passed! 209 threads created in all
-# as the last line.  The content and order of preceding lines will
-# vary across runs.
-
-def _new_thread(func, *args):
-    global TID
-    tid.acquire(); id = TID = TID+1; tid.release()
-    io.acquire(); alive.append(id); \
-                  print 'starting thread', id, '--', len(alive), 'alive'; \
-                  io.release()
-    thread.start_new_thread( func, (id,) + args )
-
-def _qsort(tid, a, l, r, finished):
-    # sort a[l:r]; post finished when done
-    io.acquire(); print 'thread', tid, 'qsort', l, r; io.release()
-    if r-l > 1:
-        pivot = a[l]
-        j = l+1   # make a[l:j] <= pivot, and a[j:r] > pivot
-        for i in range(j, r):
-            if a[i] <= pivot:
-                a[j], a[i] = a[i], a[j]
-                j = j + 1
-        a[l], a[j-1] = a[j-1], pivot
-
-        l_subarray_sorted = event()
-        r_subarray_sorted = event()
-        _new_thread(_qsort, a, l, j-1, l_subarray_sorted)
-        _new_thread(_qsort, a, j, r,   r_subarray_sorted)
-        l_subarray_sorted.wait()
-        r_subarray_sorted.wait()
-
-    io.acquire(); print 'thread', tid, 'qsort done'; \
-                  alive.remove(tid); io.release()
-    finished.post()
-
-def _randarray(tid, a, finished):
-    io.acquire(); print 'thread', tid, 'randomizing array'; \
-                  io.release()
-    for i in range(1, len(a)):
-        wh.acquire(); j = randint(0,i); wh.release()
-        a[i], a[j] = a[j], a[i]
-    io.acquire(); print 'thread', tid, 'randomizing done'; \
-                  alive.remove(tid); io.release()
-    finished.post()
-
-def _check_sort(a):
-    if a != range(len(a)):
-        raise ValueError, ('a not sorted', a)
-
-def _run_one_sort(tid, a, bar, done):
-    # randomize a, and quicksort it
-    # for variety, all the threads running this enter a barrier
-    # at the end, and post `done' after the barrier exits
-    io.acquire(); print 'thread', tid, 'randomizing', a; \
-                  io.release()
-    finished = event()
-    _new_thread(_randarray, a, finished)
-    finished.wait()
-
-    io.acquire(); print 'thread', tid, 'sorting', a; io.release()
-    finished.clear()
-    _new_thread(_qsort, a, 0, len(a), finished)
-    finished.wait()
-    _check_sort(a)
-
-    io.acquire(); print 'thread', tid, 'entering barrier'; \
-                  io.release()
-    bar.enter()
-    io.acquire(); print 'thread', tid, 'leaving barrier'; \
-                  io.release()
-    io.acquire(); alive.remove(tid); io.release()
-    bar.enter() # make sure they've all removed themselves from alive
-                ##  before 'done' is posted
-    bar.enter() # just to be cruel
-    done.post()
-
-def test():
-    global TID, tid, io, wh, randint, alive
-    import whrandom
-    randint = whrandom.randint
-
-    TID = 0                             # thread ID (1, 2, ...)
-    tid = thread.allocate_lock()        # for changing TID
-    io  = thread.allocate_lock()        # for printing, and 'alive'
-    wh  = thread.allocate_lock()        # for calls to whrandom
-    alive = []                          # IDs of active threads
-
-    NSORTS = 5
-    arrays = []
-    for i in range(NSORTS):
-        arrays.append( range( (i+1)*10 ) )
-
-    bar = barrier(NSORTS)
-    finished = event()
-    for i in range(NSORTS):
-        _new_thread(_run_one_sort, arrays[i], bar, finished)
-    finished.wait()
-
-    print 'all threads done, and checking results ...'
-    if alive:
-        raise ValueError, ('threads still alive at end', alive)
-    for i in range(NSORTS):
-        a = arrays[i]
-        if len(a) != (i+1)*10:
-            raise ValueError, ('length of array', i, 'screwed up')
-        _check_sort(a)
-
-    print 'test passed!', TID, 'threads created in all'
-
-if __name__ == '__main__':
-    test()
-
-# end of module