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* pre-commit: Upgrade psf/black for stable style 2023 Updating https://github.com/psf/black ... updating 22.12.0 -> 23.1.0 for their `2023 stable style`. * https://github.com/psf/black/blob/main/CHANGES.md#2310 > This is the first [psf/black] release of 2023, and following our stability policy, it comes with a number of improvements to our stable style… Also, add https://github.com/tox-dev/pyproject-fmt and https://github.com/abravalheri/validate-pyproject to pre-commit. I only modified `.pre-commit-config.yaml` and all other files were modified by pre-commit.ci and psf/black. * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
144 lines
4.2 KiB
Python
144 lines
4.2 KiB
Python
"""
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This is an implementation of odd-even transposition sort.
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It works by performing a series of parallel swaps between odd and even pairs of
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variables in the list.
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This implementation represents each variable in the list with a process and
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each process communicates with its neighboring processes in the list to perform
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comparisons.
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They are synchronized with locks and message passing but other forms of
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synchronization could be used.
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"""
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from multiprocessing import Lock, Pipe, Process
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# lock used to ensure that two processes do not access a pipe at the same time
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process_lock = Lock()
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"""
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The function run by the processes that sorts the list
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position = the position in the list the process represents, used to know which
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neighbor we pass our value to
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value = the initial value at list[position]
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LSend, RSend = the pipes we use to send to our left and right neighbors
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LRcv, RRcv = the pipes we use to receive from our left and right neighbors
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resultPipe = the pipe used to send results back to main
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"""
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def oe_process(position, value, l_send, r_send, lr_cv, rr_cv, result_pipe):
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global process_lock
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# we perform n swaps since after n swaps we know we are sorted
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# we *could* stop early if we are sorted already, but it takes as long to
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# find out we are sorted as it does to sort the list with this algorithm
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for i in range(0, 10):
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if (i + position) % 2 == 0 and r_send is not None:
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# send your value to your right neighbor
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process_lock.acquire()
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r_send[1].send(value)
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process_lock.release()
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# receive your right neighbor's value
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process_lock.acquire()
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temp = rr_cv[0].recv()
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process_lock.release()
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# take the lower value since you are on the left
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value = min(value, temp)
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elif (i + position) % 2 != 0 and l_send is not None:
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# send your value to your left neighbor
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process_lock.acquire()
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l_send[1].send(value)
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process_lock.release()
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# receive your left neighbor's value
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process_lock.acquire()
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temp = lr_cv[0].recv()
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process_lock.release()
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# take the higher value since you are on the right
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value = max(value, temp)
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# after all swaps are performed, send the values back to main
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result_pipe[1].send(value)
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"""
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the function which creates the processes that perform the parallel swaps
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arr = the list to be sorted
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"""
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def odd_even_transposition(arr):
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process_array_ = []
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result_pipe = []
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# initialize the list of pipes where the values will be retrieved
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for _ in arr:
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result_pipe.append(Pipe())
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# creates the processes
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# the first and last process only have one neighbor so they are made outside
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# of the loop
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temp_rs = Pipe()
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temp_rr = Pipe()
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process_array_.append(
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Process(
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target=oe_process,
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args=(0, arr[0], None, temp_rs, None, temp_rr, result_pipe[0]),
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)
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)
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temp_lr = temp_rs
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temp_ls = temp_rr
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for i in range(1, len(arr) - 1):
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temp_rs = Pipe()
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temp_rr = Pipe()
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process_array_.append(
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Process(
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target=oe_process,
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args=(i, arr[i], temp_ls, temp_rs, temp_lr, temp_rr, result_pipe[i]),
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)
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)
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temp_lr = temp_rs
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temp_ls = temp_rr
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process_array_.append(
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Process(
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target=oe_process,
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args=(
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len(arr) - 1,
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arr[len(arr) - 1],
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temp_ls,
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None,
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temp_lr,
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None,
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result_pipe[len(arr) - 1],
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),
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)
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)
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# start the processes
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for p in process_array_:
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p.start()
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# wait for the processes to end and write their values to the list
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for p in range(0, len(result_pipe)):
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arr[p] = result_pipe[p][0].recv()
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process_array_[p].join()
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return arr
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# creates a reverse sorted list and sorts it
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def main():
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arr = list(range(10, 0, -1))
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print("Initial List")
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print(*arr)
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arr = odd_even_transposition(arr)
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print("Sorted List\n")
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print(*arr)
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if __name__ == "__main__":
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main()
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